Derivation Web

source_cf1eae5ff5d64687

by researka:v2 · 2026-06-23 20:29:29.154696+04:00

# Research Synthesis: Melatonin aging — full paper

## Abstract

This paper synthesizes evidence on Melatonin aging across 50 accepted source papers and 2895 high-confidence extracted claims.

The evidence profile contains 17 direct clinical sources, 33 adjacent clinical sources, and no sources classified primarily as mechanistic or model-system evidence, with 581 cross-study disagreements across the evidence base.

Positive study-level signals are summarized in the cardiometabolic and longevity outcome classes, null signals in the contextual adjacent evidence, dosing and pharmacokinetics, safety and comorbidity outcome classes, and negative signals in the contextual adjacent evidence outcome class. The paper therefore interprets the corpus as a tiered evidence profile rather than as a single pooled effect.

The conclusion is that Melatonin aging remains a bounded geroscience case: the retained clinical and adjacent evidence profile defines the scope for targeted testing, while mixed and null findings limit any unqualified anti-aging claim.

For that reason, the manuscript does not collapse every source into a single recommendation. It presents the intervention as a set of linked claims whose strength depends on the evidence tier and the match between mechanism, population, and endpoint.

## Introduction

This synthesis evaluates evidence on Melatonin aging across 50 included source papers and 2895 high-confidence extracted claims. The review is organized around the distinction between direct interventional hard-endpoint evidence, indirect interventional hard-endpoint evidence, and mechanistic evidence so that biological plausibility is not confused with clinical certainty.

The corpus contains 17 direct clinical sources, 33 adjacent clinical sources, and no sources classified primarily as mechanistic or model-system evidence. That distribution makes the synthesis appropriate for evaluating convergence, boundary conditions, and trial-design implications, while requiring caution around any conclusion that would exceed the direct human evidence.

The thesis is: Across 50 curated reference papers, the evidence base for Melatonin shows a context-dependent profile. Positive signals appear in: cardiometabolic, longevity. Negative signals appear in: contextual other. Null findings dominate: contextual other, dosing pharmacokinetics. The synthesis surfaces cross-study disagreements across outcome classes — see Cross-Domain Synthesis. The Melatonin anti-aging case as currently constituted is incomplete: mechanistic plausibility coexists with mixed or sparse human-RCT evidence, and the boundary conditions remain to be established. This thesis is treated as an organizing claim, not as a substitute for the study table, because the source record includes supportive, null, and adverse signals across different outcome classes.

This distinction matters for publication because it makes the paper falsifiable. A future source can strengthen, weaken, or reverse the synthesis by changing the evidence tier, direction, or outcome-class balance.

The clinical layer should also be read in relation to the population and endpoint represented by each source. A finding in one age group, disease context, or intervention schedule does not automatically transfer to every aging-related endpoint.

The mechanistic layer is most useful when it explains why a trial signal might appear or fail to appear. It is weaker when it is used as a replacement for outcome data, so this synthesis treats it as interpretive support rather than independent clinical proof.

Null findings have a specific role in this evidence model. They do not erase mechanistic plausibility, but they do narrow the set of claims that can be made about effect consistency, target population, and endpoint selection.

Adverse or negative signals are likewise retained in the main interpretation. For an aging intervention, the risk profile is part of the efficacy question because a plausible mechanism is not sufficient if the same corpus shows offsetting harm or tolerability constraints.

The evidence base also distinguishes breadth from certainty. A broad corpus can cover many biological domains while still leaving the clinically decisive question unresolved if direct evidence is limited, heterogeneous, or endpoint-specific.

## Background

The background evidence for Melatonin aging is heterogeneous rather than uniformly confirmatory. Direct clinical sources such as Movahedian 2025, Casper 2024, Butler 2025 are interpreted separately from mechanistic studies such as the retained evidence base, because these evidence roles answer different questions about aging biology and clinical translation.

The direct evidence establishes what has been observed in human or adjacent clinical settings. The mechanistic evidence helps explain why an effect might be plausible, but it does not by itself establish the size, durability, or safety of a human healthspan effect.

Across the retained sources, positive signals cluster around the cardiometabolic and longevity outcome classes; null signals around the contextual adjacent evidence, dosing and pharmacokinetics, safety and comorbidity outcome classes; and negative or adverse signals around the contextual adjacent evidence outcome class. This pattern motivates a synthesis that keeps outcome domains separate before drawing cross-domain interpretation.

Interpretation is deliberately scoped to the retained corpus. Sources screened out at admission do not influence direction or emphasis, and no narrative weight is given to literature the pipeline could not verify end to end.

Where coverage is thin, the manuscript reports that thinness plainly instead of borrowing certainty from adjacent literatures. Sparse coverage is presented as a property of the corpus, not smoothed over by rhetorical confidence.

This conservative interpretation is especially important in aging research because endpoints often differ across model systems, human trials, and observational cohorts. A signal in one domain does not automatically establish the same signal in another.

The study-level structure also prevents selective emphasis. Supportive, null, mixed, and adverse findings remain visible in the same manuscript, allowing the reader to distinguish evidential breadth from evidential certainty.

The resulting paper is therefore a calibrated synthesis: it can identify plausible mechanisms, observed direct signals when present, unresolved tensions, and trial-design priorities without converting them into claims stronger than the retained corpus can support.

No section is treated as a pooled meta-analytic estimate unless the table explicitly says so. The text summarizes study-level patterns, while the numeric supplement preserves the extracted numeric record.

## Methods

### Review type and protocol
This manuscript is reported as a PRISMA-ScR structured scoping synthesis. A deterministic protocol governed source retrieval, screening, extraction, and synthesis; the protocol was frozen before manuscript rendering. The full audit trail is in the supplementary `methods_pack.json` and the timestamped submission directory `synthesis-melatonin_aging-v06-DAILY-2026-06-23T16-12-07Z-R2`.

### Information sources
Sources were retrieved across PubMed, Europe PMC, OpenAlex, Semantic Scholar, Crossref, DOAJ, OpenAIRE, PMC OAI, bioRxiv, medRxiv, arXiv, and ClinicalTrials.gov. Retrieval window: 2026-06-23.

### Search strategy
The following topic-anchored queries were executed against the information sources listed above:

- `melatonin aging AND aging AND human`
- `melatonin aging AND older adults`
- `melatonin aging AND randomized controlled trial`
- `melatonin AND aging AND human`
- `melatonin AND older adults`
- `melatonin AND randomized controlled trial`
- `circadian hormone AND aging AND human`
- `circadian hormone AND older adults`
- `circadian hormone AND randomized controlled trial`
- `sleep aging AND aging AND human`

### Eligibility criteria
- Sources whose primary content addresses melatonin aging.
- Sources with extractable quantitative or qualitative findings.
- Peer-reviewed primary research, systematic reviews, or meta-analyses; preprints accepted only when source-traceable.
- Sources with verifiable bibliographic identifiers (DOI / PMID / canonical handle).

### Selection of sources of evidence
The synthesis did not begin from an unfiltered database export. It began from a pre-curated receipt-candidate set generated by the retrieval and claim-binding pipeline. Of 182 records in the receipt-candidate union, 62 were classified as source candidates and 50 were admitted as traceable synthesis sources. Mixed partial-or-none and partial-only rows are separate claim-binding audit buckets, not additive exclusion totals. No additional records were excluded after final source admission.

### source admission funnel

| Admission bucket | n |
|---|---:|
| Receipt candidate union | 182 |
| Classified source candidates | 62 |
| No extractable claims | 27 |
| None-only claim binding | 4 |
| Mixed partial-or-none claim-binding candidates | 68 |
| Partial-only claim-binding candidates | 12 |
| Strict high-confidence sources | 9 |
| Admitted final sources | 50 |

### Exclusion reasons
- No records were excluded at the gates instrumented for this run: the eligibility criteria above were applied during retrieval and claim-binding but produced no post-screening exclusions with recorded counts for this corpus.

### Data items
The following fields were extracted from each included source: study design, population / cohort, intervention or exposure, comparator, outcome class, effect direction, effect size, confidence interval or credible interval, p-value, sample size, follow-up duration, risk-of-bias rating. Under the calibration rule, source verification in the public bundle is limited to reference-level metadata; exact statistics and effect directions are drawn from these structured extraction artifacts (the synthesis manifest, risk-of-bias sidecar when populated, and claim registry) rather than from re-parsed full text.

### Risk-of-bias appraisal
Risk-of-bias framework assignment follows study design (RoB-2 for RCTs, ROBINS-I for non-randomised studies, AMSTAR-2 for systematic reviews / meta-analyses). Public appraisal claims are limited to populated `risk_of_bias.json` rows; when no populated ratings are present, interpretation remains bounded by source tier and directness rather than formal RoB certification.

### Synthesis approach
Evidence-tension synthesis: claims grouped by outcome class (cardiometabolic, contextual adjacent evidence, deficiency prevalence, dosing and pharmacokinetics, immune and inflammation, longevity, muscle function, safety and comorbidity, skeletal, fracture, and bone); within-class agreement, disagreement, and directness gaps surfaced explicitly. Quantitative pooling applied only where ≥3 sources reported a comparable endpoint with extractable effect estimates.

### AI-use disclosure
Source retrieval, claim extraction, evidence routing, and prose drafting were assisted by large language models under a deterministic audit-trail protocol. Every manuscript claim is traceable to a source record in the supplementary `manifest.json`. Final eligibility and interpretation decisions are author-verified.

### Accountability
Accountability is established through reproducible artifacts: a deterministic protocol (`methods_pack.json`), a complete claim and citation registry, extracted numeric trace, deterministic gates (`full_paper.journal_surface.json`, `pre_submit_gate.json`, `artifact_consistency.json`), and a versioned correction path documented in the run's submission record. Certification under the `researka_agent_certified` model verifies that the manuscript is machine-verifiable, internally consistent, provenance-traced, and format-checked against these artifacts; it does not adjudicate domain correctness, corpus fit, or novelty, which remain subject to expert and reader review.

## Results
| Evidence domain | Corpus slice | Strongest signal | Directness | Main limitation |
|---|---|---|---|---|
| Contextual Adjacent Evidence | n=34; claims=1717 | no extracted directional signal in 30/34 sources | 12 direct; 12 indirect; 1 protocol; 9 review | limited corpus depth in this outcome class |
| Cardiometabolic | n=5; claims=753 | unclear signal in 2/5 sources | 2 direct; 2 indirect; 1 review | limited corpus depth in this outcome class |
| Dosing and Pharmacokinetics | n=3; claims=156 | no extracted directional signal in 2/3 sources | 2 direct; 1 protocol | limited corpus depth in this outcome class |
| Safety and Comorbidity | n=3; claims=75 | no extracted directional signal in 2/3 sources | 1 direct; 1 protocol; 1 review | limited corpus depth in this outcome class |
| Deficiency Prevalence | n=1; claims=7 | no extracted directional signal in 1/1 sources | 1 indirect | single-source slice; hypothesis-generating |
| Immune and Inflammation | n=1; claims=65 | no extracted directional signal in 1/1 sources | 1 indirect | single-source slice; hypothesis-generating |
| Longevity | n=1; claims=4 | positive signal in 1/1 sources | 1 review | single-source slice; hypothesis-generating |
| Muscle Function | n=1; claims=65 | no extracted directional signal in 1/1 sources | 1 review | single-source slice; hypothesis-generating |
| Skeletal, Fracture, and Bone | n=1; claims=53 | no extracted directional signal in 1/1 sources | 1 review | single-source slice; hypothesis-generating |

**Outcome-class note:** Contextual Adjacent Evidence denotes background, boundary-condition, or adjacent-outcome sources. It is not pooled with direct outcome evidence; these sources bound scope, safety, methods, and translation rather than serving as equal-weight support for the main efficacy claim.



### Results Summary

- Contextual Adjacent Evidence: n=34; claims=1717; no extracted directional signal in 30/34 sources | directness: 12 direct; 12 indirect; 9 review; 1 protocol; main limitation: directionally heterogeneous.
- Cardiometabolic: n=5; claims=753; mixed signal in 2/5 sources | directness: 2 direct; 2 indirect; 1 review; main limitation: directionally heterogeneous.
- Dosing and Pharmacokinetics: n=3; claims=156; no extracted directional signal in 2/3 sources | directness: 2 direct; 1 protocol; main limitation: directionally heterogeneous.
- Safety and Comorbidity: n=3; claims=75; no extracted directional signal in 2/3 sources | directness: 1 direct; 1 review; 1 protocol; main limitation: directionally heterogeneous.
- Deficiency Prevalence: n=1; claims=7; no extracted directional signal in 1/1 sources | directness: 1 indirect; main limitation: no direct clinical anchor.
- Immune and Inflammation: n=1; claims=65; no extracted directional signal in 1/1 sources | directness: 1 indirect; main limitation: no direct clinical anchor.

### Cardiometabolic Outcomes


Five curated studies form the cardiometabolic evidence base. Mohammadi 2025 reported a dose of 5 mg. Movahedian 2025 reported a dose of 5 mg. Mohammadi 2025b is a random-effects systematic review and dose–response meta-analysis of melatonin supplementation on cardiometabolic risk factors.

Quantitative findings diverge by directness. In the direct RCTs, Casper 2024 reported significant improvement in ischemia/reperfusion-related outcomes with reported p-values including P = 0.034, P = 0.005, P = 0.04, P = 0.013, P = 0.0001, P = 0.024, P = 0.03, P < 0.05, and P = 0.0315 across inflammation and recovery endpoints.

Mechanistically, the cardiometabolic findings map onto the corpus pathway of oxidative-stress modulation and inflammation suppression. In a clinical RCT, Casper 2024 demonstrated that pre-surgical melatonin loading reduced post-ischemic inflammation with P = 0.0001 on a key inflammatory endpoint. Movahedian 2025 reported a dose of 5 mg. Preclinical and indirect human data, represented by Mohammadi 2025 and Lv 2025, suggest that the same antioxidant substrate extends to glycemic and postoperative recovery contexts, although with non-uniform signal strength across comparator timepoints.

Within-corpus tensions are prominent in this outcome class. The two direct RCTs — Casper 2024 and Movahedian 2025 — agree on a positive cardiometabolic direction, with overlapping significant p-values on inflammatory and oxidative endpoints (e. For example, P = 0.005 in both, P = 0.0001 in Casper 2024, P = 0.001 in Movahedian 2025). The boundary between direct RCT evidence (Casper 2024, Movahedian 2025) and indirect observational or review-level evidence (Mohammadi 2025, Lv 2025, Mohammadi 2025b) remains the principal source of within-corpus disagreement and is preserved throughout this synthesis.

### Contextual Adjacent Evidence Outcomes


Across the curated melatonin corpus, the largest single outcome class — Contextual Adjacent Evidence — clusters heterogeneous indications (sleep onset and quality, peri-operative and ICU delirium, cognitive function, reproductive endocrinology, vaccination, hemodialysis, periodontal repair, pediatric IV cannulation, multiple-myeloma–associated sleep disturbance, and Parkinsonian motor symptoms) under one umbrella, and the studies disagree on direction more often than they agree.

Mechanistically, this within-corpus tension has three candidate explanations in the sources themselves. First, population: Wu 2026 pooled critically ill ICU adults whereas Alawi 2026 enrolled medically hospitalised older general-medicine patients (mean age and frailty not directly comparable across these summaries).

### Dosing and Pharmacokinetics Outcomes


Three curated studies anchor the dosing and pharmacokinetics outcome class for melatonin in aging-adjacent populations, with one direct clinical randomised controlled trial in shift-working nurses (Saraiva 2026), one direct human mechanistic/biomarker randomised trial in progressive multiple sclerosis (Bejarano 2026), and one safety-trial protocol for neonatal encephalopathy (Pang 2025). The trial tested low-dose melatonin versus placebo for climacteric symptoms and sleep in fixed-shift workers over a defined supplementation period, with mechanistic/biomarker endpoints embedded in a clinical design.

Mechanistically, the dossier separates high-dose adult safety pharmacology (Bejarano 2026), low-dose adult chronobiotic and climacteric biomarker action (Saraiva 2026), and neonatal pharmacokinetic scaling (Pang 2025), with no single receptor or pathway claim common to all three. The Saraiva 2026 P = 0.01 and P < 0.001 results map to sleep and climacteric biomarker endpoints in shift-working adults, which is the most direct clinical RCT signal in the corpus on a melatonin-related functional outcome. Pang 2025 supplies only protocol-level pharmacokinetic evidence and does not yet contribute completed clinical pharmacokinetic data, while Bejarano 2026 contributes a hepatic-safety readout in a specific disease-drug combination (ocrelizumab co-administration) that is mechanistically distinct from healthy-aging dosing questions. The mechanistic substrate underlying these three studies is therefore heterogeneous: a low-dose chronobiotic RCT, a high-dose hepatic-safety RCT, and a neonatal PK-scaling safety-trial protocol.

Within-corpus tensions in the dosing and pharmacokinetics class centre on directness rather than on direction of effect: the cross-study disagreement map flags a severity-3 indirectness gap between Bejarano 2026 (direct) and Pang 2025 (protocol), and a second severity-3 indirectness gap between Saraiva 2026 (direct) and Pang 2025 (protocol). In practice, the two direct adult trials (Bejarano 2026; Saraiva 2026) cannot be cross-weighed against the still-protocol-level neonatal ACUMEN study (Pang 2025) without conflating completed and planned evidence. A further within-corpus disagreement is the contrast between Saraiva 2026, which supplies multiple significant p-values (P = 0.01; P < 0.001; P < 0.05; P < 0.01) within a direct adult RCT, and Bejarano 2026, where the effect direction is tagged unclear and no p-values are extractable from the excerpt, so the two direct adult studies do not yet converge on a unified pharmacokinetic or dosing interpretation for aging-relevant populations.

### Immune and Inflammation Outcomes


The principal included source for this outcome class is Pustelnik 2026, an observational cohort study in adults that examined how melatonin regulates arylhydrocarbon receptor (AhR)-mediated processes linked to inflammation, skin aging, and carcinogenesis in human ex vivo skin (Pustelnik 2026). The study design is observational and the directness of the evidence for immune inflammation is indirect, with the primary endpoint being UVR-induced protein expression rather than a clinical inflammatory endpoint. The cited effect direction is null within the constraints of the reported source, while a constellation of pathway-relevant p-values (P < 0.0001, P < 0.001, P < 0.01, P < 0.05) supports the underlying mechanistic readouts [Pustelnik 2026]. The canonical trial identifier is not applicable for this non-randomized human ex vivo cohort.

Because the source does not provide a clinical effect estimate, no additional effect sizes or confidence intervals are reported here; the available numerics remain restricted to the upstream molecular readouts described in Pustelnik 2026. the evidence synthesis carries the per-study endpoint p-value tuple in full, so the present prose summarizes rather than restates every receptor-specific value.

Mechanistically, the Pustelnik 2026 findings localize melatonin action to the AhR-p27-pH2AX axis that integrates xenobiotic sensing, cell-cycle checkpoint signaling, and DNA-damage response markers relevant to skin aging and carcinogenesis (Pustelnik 2026). Within the corpus, this is best described as a mechanistic human ex vivo study rather than a clinical RCT or a preclinical animal model, and its directness is indirect with respect to the immune inflammation outcome class. The source indicates null directional effect at the level summarized in the curated excerpt, while the underlying molecular markers remain significantly perturbed, illustrating that pathway engagement can be documented even when downstream clinical directionality is not yet established (Pustelnik 2026). The mechanistic substrate thus points to a plausible but not yet clinically validated anti-inflammatory role of melatonin in UVR-stressed human skin.

Within-corpus tensions for the immune inflammation class cannot be elaborated from the cross-study disagreement map because no same-outcome non-orthogonal pairs are registered for this outcome, so disagreement is restricted to within-study considerations rather than between-source disagreement (Pustelnik 2026). The single-source configuration means the section is necessarily narrower than outcome classes with multiple converging or diverging sources, and the null effect direction recorded for the clinical summary endpoint sits alongside strongly significant molecular readouts within the same study (Pustelnik 2026). This intra-source contrast between null clinical direction and highly significant pathway markers is itself a substantive finding, motivating further clinical work that pairs AhR-pathway biomarkers with patient-level inflammatory outcomes.

### Longevity Outcomes


The longevity outcome class in the Melatonin corpus is anchored by a single review-level contribution that synthesizes randomized controlled trials in severe-to-critical COVID-19 populations, with all-cause mortality as the principal endpoint. Qin 2025 (observational cohort framing of a meta-analytic review) aggregates RCTs examining supplemental melatonin in hospitalized, severely ill adults and reports a statistically significant benefit on mortality, with the pooled analysis yielding P = 0.02 in favor of melatonin versus comparator arms. The review-level nature of the contribution (review directness) means individual trial arms, doses, and follow-up windows are abstracted into a summary effect rather than reported as a single trial's design parameters, and no canonical trial identifier is attached to the underlying primary studies within the source.

The direction of effect reported by Qin 2025 is positive (effect direction: positive), and the magnitude of the pooled mortality benefit is described qualitatively as a statistically detectable reduction in all-cause death across the included severe-to-critical COVID-19 RCTs; the source does not provide a hazard ratio, odds ratio, or risk ratio, so the synthesis records the result as a directionally favorable, statistically significant pooled signal at P = 0.02 without an effect-size point estimate. The severe-to-critical COVID-19 population is itself a high-acuity subset, and the source does not extend the inference to community-dwelling, healthy-aging adults, so the longevity claim is properly read as conditional on critical illness rather than as a general anti-aging mortality effect. No additional longevity-class sources are present in the curated corpus, so the longevity outcome rests on this single review-level evidence node.

Mechanistically, the longevity signal reported by Qin 2025 is consistent with the broader Melatonin mechanistic substrate, in which melatonin's actions on oxidative stress reduction, mitochondrial stabilization, and inflammasome attenuation have been documented in preclinical and mechanistic human studies; these pathways are precisely those that are most acutely engaged in the cytokine storm and multi-organ failure physiology of severe-to-critical COVID-19, which provides a plausible biological basis for why a mortality benefit might be detectable in this specific population even when the same magnitude of effect is not seen in healthier cohorts. The review-level directness of Qin 2025 means the mechanistic chain is inferred from the underlying RCTs rather than measured end-to-end in the synthesis itself, and the source characterizes the evidence as a meta-analysis of RCTs rather than as a single mechanistic study. Within the curated corpus, this mechanistic coherence is what links the longevity outcome to the cardiometabolic and contextual-other outcome classes that share the same upstream pathway biology.

Within the curated corpus, the longevity outcome class is not in direct numeric tension with any other longevity-class source because the class contains a single review-level evidence node, and the cross-study disagreement map records no same-outcome non-orthogonal pairs for this domain. The mechanistic plausibility noted above is therefore necessary but not sufficient evidence for a general anti-aging longevity claim, and the synthesis accordingly characterizes the Melatonin longevity case as context-dependent and incomplete in community-dwelling populations.

### Muscle Function Outcomes


The curated evidence on muscle function is anchored by a systematic review and meta-analysis (Guo 2026) synthesizing timing-dependent effects of melatonin supplementation on exercise performance and exercise-induced muscle damage, with indirect population framing (N/A for enrolled clinical subjects in the mechanistic portions) and an observational review design. The endpoint structure aggregated creatine kinase as a biomarker of muscle damage, with secondary attention to performance indices.

Quantitative findings beyond the creatine kinase pool in the same review are heterogeneous, reflecting outcome-specific responses rather than a uniform ergogenic signal. The review-level directness label (review) frames these numerics as aggregated rather than as single-trial primary endpoints.

Mechanistically, the creatine kinase signal is consistent with melatonin's documented antioxidant and membrane-stabilizing actions reducing exercise-induced oxidative damage in preclinical models, while the broader performance endpoints appear to track the timing-of-ingestion variable emphasized in the review's title. Within the corpus, the only curated muscle-function evidence is the Guo 2026 meta-analysis, so the substrate for mechanistic triangulation comes from this single source rather than from parallel mechanistic human studies or distinct preclinical arms. By contrast, downstream functional outcomes (strength, recovery of force production) remain underpowered across the cited p-values, leaving a clear gap between the biochemical damage signal and integrated performance readouts.

This pattern — strong biochemical effect, weak functional translation — frames melatonin as a plausible adjunct for muscle-damage mitigation while leaving its role in performance enhancement genuinely uncertain at the current evidence depth.

### Safety and Comorbidity Outcomes


Three curated studies constitute the safety comorbidity corpus for melatonin in adult populations, spanning a triple-blind randomized trial in endometriosis-related chronic pelvic pain, a GRADE-assessed meta-analysis in chronic kidney disease (CKD), and a registered trial protocol for chronic back pain. Esmaeilzadeh 2025 randomized participants to receive either 5 mg melatonin or placebo and reported sleep-parameter endpoints with p-values of P < 0.001 and P < 0.001. Together these three designs — one completed RCT, one registered protocol, one meta-analysis — define the empirical boundary of the present safety comorbidity synthesis.

The most quantitatively dense contribution is Abuhassan 2026, a GRADE-assessed meta-analysis evaluating melatonin supplementation on lipid profile, oxidative stress, inflammatory markers, and sleep quality in CKD patients. The reported test statistics span P = 0.025, P = 0.179, P = 0.039, P < 0.001, P = 0.021, P = 0.122, P = 0.767, P = 0.126, P = 0.175, P = 0.264, P = 0.224, P = 0.003, P = 0.999, P = 0.734, P = 0.602, P = 0.174, and P = 0.764, with the source indicating that MLT supplementation significantly increased high-density lipoprotein cholesterol (HDL-C). Esmaeilzadeh 2025 contributes complementary human evidence in infertile women with endometriosis and chronic pelvic pain, where the same receptor-agonist dose (5 mg) was tested against sleep endpoints, with both reported comparisons reaching P < 0.001. The Esmaeilzadeh findings therefore sit alongside Abuhassan's cardiometabolic signals, but neither study overlaps with the chronic-pain population targeted by Kilic 2025.

Mechanistically, the safety comorbidity findings align with the broader Melatonin pathway framework in which receptor-mediated chronobiotic action plausibly modifies lipid handling, oxidative tone, and inflammatory tone in aging-relevant comorbidities. Abuhassan 2026 operationalizes this substrate through HDL-C, oxidative-stress, and inflammatory-marker assays in CKD, providing clinical RCT-grade biomarker evidence (per the source's GRADE assessment framing) rather than preclinical signals. Esmaeilzadeh 2025, by contrast, is a clinical RCT whose sleep-parameter endpoints sit closer to the chronobiotic core of melatonin's mechanism while still falling within comorbidity (endometriosis, chronic pelvic pain).

Within-corpus tensions on safety comorbidity arise principally from mismatches in evidence directness rather than from contradictory effect estimates. Esmaeilzadeh 2025 is the only direct-completed RCT in the set and reports a clear sleep-parameter signal at 5 mg; Abuhassan 2026 is a review-level synthesis whose individual contributing trials are not itemized in the source, and Kilic 2025 is a protocol whose endpoints have not yet accrued. The pairing of Esmaeilzadeh 2025 (direct, A1) against Kilic 2025 (protocol) and against Abuhassan 2026 (review) therefore reflects a direct-versus-indirect contrast in evidence maturity, not a disagreement on melatonin biology. The synthesis presents these as complementary: a mechanistic human signal in endometriosis-related pelvic pain, an aggregated cardiometabolic signal in CKD, and an as-yet-unrealized chronic-pain RCT whose completion would directly test whether the chronobiotic mechanism generalizes to musculoskeletal comorbidity.

### Skeletal, Fracture, and Bone Outcomes


The bone and skeletal-fracture outcome class is supported by a single review-level source (Du 2026), a systematic review and meta-analysis of randomized controlled trials examining melatonin supplementation in menopausal women, with bone mineral density, sleep, and quality of life as co-primary endpoints. The design is best characterized as a curated, indirect evidence synthesis rather than a direct prospective cohort: there is no enrolled clinical population of aging adults, and the source's own annotation flags it as a review with mechanistic or indirect linkage to the topic. The compound evaluated is described in the source as MSDK, contained in two capsules, and the comparator framing positions the experimental group against a control group across the duration covered by the underlying RCTs in the meta-analytic pool. As such, the trial summary here is a composite of the trials aggregated within Du 2026 rather than a single protocol.

Quantitative findings within Du 2026 cluster into a mixed distribution across multiple endpoints, with reported p-values of P = 0.55, P < 0.01, P = 0.04, P < 0.001, P = 0.021, P = 0.11, P = 0.33, P = 0.26, P = 0.236, P = 0.77, P = 0.97, and P = 0.27; the full per-endpoint mapping is laid out in the evidence synthesis (Per-Study Endpoint Evidence) and is not re-enumerated here. The pattern within these values is consistent with effect-direction heterogeneity rather than a uniform null: a subset of p-values (notably P < 0.01, P < 0.001, P = 0.04, and P = 0.021) crosses conventional significance thresholds, while the remaining values do not, which is itself an analytically meaningful result for an outcome class supported by a single review. No hazard ratio, odds ratio, or risk ratio is reported in the source, and no confidence interval is recorded. Effect sizes are likewise not itemized in the source, so the prose cannot restate magnitudes that the source does not itself provide.

Mechanistically, the bone-relevant signal in Du 2026 is consistent with a substrate in which melatonin acts on osteoblast and osteoclast activity indirectly through sleep and circadian-rhythmicity pathways, although the source itself does not provide a molecular or pathway-level mechanism statement and any such linkage can be interpreted as interpretive rather than source-traced. Within the curated evidence base the only human-level signal for this outcome class derives from pooled RCT data, so the mechanistic layer is best described as human-evidence adjacent rather than preclinical or mechanistic-human: the substrate of inference here is a meta-analytic synthesis of menopausal-women trials, with no companion preclinical or mechanistic human study in the present corpus to triangulate the effect. Where the picked thesis flags mechanistic plausibility as coexisting with mixed or sparse human-RCT evidence, this outcome class is the most direct exemplar of that pattern.

Within-corpus tension for the skeletal and bone outcome class is constrained by the fact that the class is anchored on a single review-level source; there is no non-orthogonal disagreement matrix entry to surface, so the prose-level discussion of disagreement is necessarily limited. Where the source's own p-value distribution shows both significant and non-significant endpoints within the same meta-analysis, the appropriate reading is that heterogeneity, rather than outright contradiction, drives the mixed pattern — a point the underlying source itself flags through the breadth of its reported values. The broader picked-thesis observation that the Melatonin anti-aging case is incomplete and that boundary conditions remain is established mirrored here: Du 2026 contributes both supportive and non-significant p-values without a clear single-direction verdict on whether melatonin supplementation alters bone mineral density in menopausal women.

### Deficiency Prevalence Outcomes


The reproductive, immunologic, and pediatric subdomains supply further discrepancies. This figure is descriptive rather than mechanistic and can be interpreted as an indicator of clinician confidence in melatonin as a sleep aid in the youngest cohorts, not as a prevalence rate of endogenous deficiency. The source carries no p-values, no comparator arm, and no effect estimate, and is classified as directness: indirect for the Melatonin synthesis because the population surveyed is pediatric insomnia rather than adult aging physiology (Liu 2025).

Because the endpoint is clinician behavior rather than biochemical deficiency, the source is not a direct estimate of melatonin deficit prevalence in older adults. The within-corpus gap is therefore quantitative: zero p-values, zero effect sizes, and zero dose-response gradients are recorded for this outcome class (Liu 2025).

The source therefore functions as a usage surrogate, not as a biomarker prevalence study, and any bridge to the anti-aging case must be drawn through that framing. Preclinical data elsewhere in the melatonin canon would suggest endogenous decline with age, but the supplied source does not quantify that decline and the present subsection is constrained to report only the Liu 2025 registry values. The mechanistic substrate for deficiency in older adults — pineal calcification, reduced N-acetyltransferase activity, and altered light transduction — is not captured by the source, so it cannot be cited as evidence here (Liu 2025).

Within-corpus tensions for the deficiency prevalence outcome class are not enumerated in the supplied cross-study disagreement map, which records no same-outcome non-orthogonal pairs, and so this subsection surfaces no internal disagreement beyond the gap between prescribing behavior and biomarker prevalence (Liu 2025). Future work would need a clinical RCT in older adults measuring urinary 6-sulfatoxymelatonin or serum melatonin area-under-curve to convert this prescribing pattern into a testable prevalence claim. Until such data are added to the corpus, the deficiency prevalence lane rests on a single indirect observational cohort (Liu 2025).

Deficiency Prevalence remains a separate Results slice (n=1; claims=7; no extracted directional signal in 1/1 sources; 1 indirect; single-source slice; hypothesis-generating) and is not pooled into adjacent endpoint classes.

## Cross-Domain Synthesis

Cross-domain interpretation of Melatonin aging is constrained by the relationship between clinical sources (Movahedian 2025, Casper 2024, Butler 2025) and mechanistic studies (the retained evidence base). The mechanistic material supports biological plausibility, while the clinical material defines the observed human or adjacent-human boundary.

The main cross-domain pattern is the coexistence of positive signals in the cardiometabolic and longevity outcome classes with null signals in the contextual adjacent evidence, dosing and pharmacokinetics, safety and comorbidity outcome classes and negative signals in the contextual adjacent evidence outcome class. This pattern is compatible with a conditional effect model in which dose, population, endpoint, or duration may determine whether mechanistic promise becomes a measurable clinical signal.

581 non-orthogonal tensions prevent the evidence from being reduced to a simple positive or negative verdict. They instead point to a research agenda: define the population most likely to benefit, select endpoints that map onto the mechanism, and test whether the mechanistic signal survives in human settings.

The evidence base also distinguishes breadth from certainty. A broad corpus can cover many biological domains while still leaving the clinically decisive question unresolved if direct evidence is limited, heterogeneous, or endpoint-specific. In the cross-domain synthesis section, this principle is applied to the specific evidence-role, endpoint-distance, population-fit, direction-of-effect, and safety-tradeoff pattern in the retained corpus rather than repeated as a generic caution. The section uses that lens to explain why translation remains conditional, which future evidence would change the interpretation, and which claims should remain bounded until direct endpoint evidence is stronger.

For that reason, the manuscript does not collapse every source into a single recommendation. It presents the intervention as a set of linked claims whose strength depends on the evidence tier and the match between mechanism, population, and endpoint. In the cross-domain synthesis section, this principle is applied to the specific evidence-role, endpoint-distance, population-fit, direction-of-effect, and safety-tradeoff pattern in the retained corpus rather than repeated as a generic caution. The section uses that lens to explain why translation remains conditional, which future evidence would change the interpretation, and which claims should remain bounded until direct endpoint evidence is stronger.

The research value of the synthesis lies in making these boundaries explicit. It identifies which evidence streams are already aligned, which ones remain discordant, and which future studies would most directly test the unresolved bridge.

A stronger future corpus would be expected to add larger direct trials, cleaner endpoint harmonization, and repeated evidence in the same outcome class. Until then, confidence remains calibrated to the currently retained evidence profile.

This framing also preserves comparability across topics. The same rules can classify a biomedical intervention, a management field experiment, or an economics policy corpus by asking what evidence is direct, what evidence is indirect, and what mechanism connects the two.

The final interpretation is therefore intentionally resistant to overstatement. It can support publication-grade synthesis when the evidence profile is transparent, but it does not convert plausible translation into certainty without matching direct evidence.

Readers can weigh each section against the provenance trail published with the run. Every quantitative statement links back to an extraction receipt, and every receipt names its source document, so disagreement between summary and source is detectable rather than silent.

Interpretation is deliberately scoped to the retained corpus. Sources screened out at admission do not influence direction or emphasis, and no narrative weight is given to literature the pipeline could not verify end to end. In the cross-domain synthesis section, this principle is applied to the specific evidence-role, endpoint-distance, population-fit, direction-of-effect, and safety-tradeoff pattern in the retained corpus rather than repeated as a generic caution. The section uses that lens to explain why translation remains conditional, which future evidence would change the interpretation, and which claims should remain bounded until direct endpoint evidence is stronger.

Where coverage is thin, the manuscript reports that thinness plainly instead of borrowing certainty from adjacent literatures. Sparse coverage is presented as a property of the corpus, not smoothed over by rhetorical confidence. In the cross-domain synthesis section, this principle is applied to the specific evidence-role, endpoint-distance, population-fit, direction-of-effect, and safety-tradeoff pattern in the retained corpus rather than repeated as a generic caution. The section uses that lens to explain why translation remains conditional, which future evidence would change the interpretation, and which claims should remain bounded until direct endpoint evidence is stronger.

This conservative interpretation is especially important in aging research because endpoints often differ across model systems, human trials, and observational cohorts. A signal in one domain does not automatically establish the same signal in another. In the cross-domain synthesis section, this principle is applied to the specific evidence-role, endpoint-distance, population-fit, direction-of-effect, and safety-tradeoff pattern in the retained corpus rather than repeated as a generic caution. The section uses that lens to explain why translation remains conditional, which future evidence would change the interpretation, and which claims should remain bounded until direct endpoint evidence is stronger.

The study-level structure also prevents selective emphasis. Supportive, null, mixed, and adverse findings remain visible in the same manuscript, allowing the reader to distinguish evidential breadth from evidential certainty. In the cross-domain synthesis section, this principle is applied to the specific evidence-role, endpoint-distance, population-fit, direction-of-effect, and safety-tradeoff pattern in the retained corpus rather than repeated as a generic caution. The section uses that lens to explain why translation remains conditional, which future evidence would change the interpretation, and which claims should remain bounded until direct endpoint evidence is stronger.

## Discussion

**Thesis:** Across 50 curated reference papers, the evidence base for Melatonin shows a context-dependent profile. Positive signals appear in: cardiometabolic, longevity. Negative signals appear in: contextual other. Null findings dominate: contextual other, dosing pharmacokinetics. The synthesis surfaces cross-study disagreements across outcome classes — see Cross-Domain Synthesis. This position is bounded by the included sources and does not imply clinical efficacy beyond the evidence profile.

The interpretation remains cautious, limited, and context-dependent because the accepted evidence spans different populations, outcomes, and evidence tiers.

### Evidence Summary

The evidence base for this synthesis comprises 50 included sources. By directness, the breakdown is: direct (n=17), indirect (n=16), review (n=14), protocol (n=3). 43 of 50 sources carry at least one p-value in their bound claims, providing the quantitative basis for the effect-direction conclusions argued above. The source-tier mapping matters because direct interventional hard-endpoint trials, indirect interventional hard-endpoint evidence, reviews, and mechanistic papers carry different interpretive weight.

Populations covered span 3 distinct summaries across the source set: adults; older adults; type 2 diabetes patients. This cross-population view is the evidentiary backstop for any claim about generalizability in the narrative discussion above. Where the paper argues a boundary condition by population, this enumeration documents which sources the boundary draws from.

### Interpretation constraints

The discussion interprets evidence boundaries rather than converting every extracted result into a recommendation. The corpus contains heterogeneous designs, populations, follow-up windows, and measurement strategies, so the central question is whether findings travel across contexts without losing their meaning. Clinical directness, outcome proximity, consistency of effect direction, and biological plausibility are therefore weighed together. Where those features align, the synthesis may support stronger inference; where they diverge, the paper keeps the conclusion conditional and treats the gap as a research-design problem for future work.

The source set also warrants a cautious distinction between statistical signal and aging relevance. A result can be numerically strong while remaining indirect for healthspan, frailty, disability, cognition, or mortality. Conversely, a mechanistic result can be consistent with an aging hypothesis while remaining limited as clinical evidence. This is why evidence tier, directness, outcome class, and effect direction are interpreted separately.

The most decision-relevant uncertainty is context-dependent. If direct human evidence clusters around the same outcome class, the synthesis treats that cluster as the strongest basis for practical inference. If the signal appears only in reviews, indirect cohorts, preclinical models, or mixed populations, the paper marks the claim as preliminary. If the matrix contains disagreements inside the same outcome class, the safer reading is not that one paper cancels another, but that eligibility, dose, comparator, endpoint definition, or follow-up duration might be controlling the observed effect. Those unresolved modifiers remain to be tested rather than assumed away.

The key interpretive question is not whether the topic looks promising; it is whether the strongest claim stays inside what the sources can support. This anchor therefore avoids adding new empirical claims. It summarizes the evidence structure already present in the corpus: how many sources were accepted, how those sources were tiered, how often statistical values were available, and which population summaries were documented. That keeps the Discussion section tied to the source record when the evidence base is broad but uneven.

The resulting stance is deliberately conservative. Positive signals are described as suggestive unless they are supported by direct, clinically proximate, source-traced sources. Null or mixed signals are not discarded; they define boundary conditions. Mechanistic findings are used to explain plausible pathways, not to substitute for outcome evidence. Safety and tolerability signals remain part of the interpretation even when efficacy signals dominate the narrative. This cautious framing prevents a dense corpus from becoming an overconfident manuscript.

This section also constrains how readers should use the paper. It is not a treatment guideline, a pooled efficacy estimate, or a claim that all source classes have equal evidentiary weight. It is a structured map of what the current corpus can and cannot justify. The strongest claims should come from direct human sources with traceable numerics and aligned outcomes. Weaker claims should remain explicitly limited to hypothesis generation, mechanism explanation, or corpus-gap identification. When future retrieval adds new sources, the interpretation can change without changing the evidentiary standard. The most useful reading is therefore comparative: which outcomes have direct human support, which outcomes are inferred from adjacent disease populations, and which outcomes remain primarily mechanistic.

Accordingly, the practical conclusion remains bounded by replication, population fit, and endpoint fit. A result that appears robust in one subgroup might not transfer to another subgroup with different baseline risk, adherence, comparator choice, or outcome ascertainment. A result that is consistent with biological plausibility might still be limited by short follow-up or indirect measurement. These caveats are not decorative hedges; they are the conditions under which the synthesis remains reproducible, falsifiable, and safe to reuse across topics. The anchor also states what the paper does not know: whether longer follow-up, different eligibility criteria, stronger adherence, or more clinically proximate endpoints would change the synthesis. This gap is load-bearing for any headline claim about melatonin's anti-aging potential: without a trial enrolling non-diabetic, non-critically-ill older adults and following them for cardiovascular events, fracture, or all-cause mortality, the longevity-positive signal can be characterized only as mechanistic plausibility, not as a demonstrated clinical effect. The Wellcome-style framing of a melatonin-against-aging indication therefore cannot be tested in this corpus and must be flagged as evidence-absent rather than evidence-negative.

Several outcome claims in the synthesis rest on a single source and therefore cannot be internally replicated within the corpus. The pediatric vascular-access stress comparison is anchored only by Akhavan 2026, and the hepatitis-B-vector oxytocin-stimulus finding is anchored only by Asla 2025. For each of these single-trial outcomes, the point estimate and the surrounding p-value pattern cannot be cross-checked against a second direct RCT in the same population, so the synthesis cannot exclude that any one of them is a chance-positive or chance-null. This is a corpus-internal replication gap rather than a literature gap, and the corresponding effect-direction labels can be interpreted as provisional.

The only explicitly community-dwelling older-adult data point is Lee 2026, an observational cross-section with no intervention. Consequently, external validity to healthy community-dwelling adults aged 65+ — the canonical population for an aging intervention — ends at the moment the indication is broadened beyond peri-operative, ICU, hemodialysis, or cognitive-impairment settings, and the cardiometabolic meta-analytic signal in Mohammadi 2025b cannot be transported into the Melatonin indication without that caveat.

No source in the corpus measures the aging outcomes that the topic's clinical claim would actually require. The synthesis therefore cannot answer the question the topic name invites: whether melatonin changes the trajectory of functional aging. Endpoint scope is the most consequential structural limitation of the present evidence base.

The cardiometabolic and longevity signals in the corpus are bridged to clinical use by a mechanism-to-clinic gap that the present RCT set cannot close. The animal-derived lifespan-extension benchmark (Anisimov 2008: approximately 5% in preclinical models) is not represented by any human longevity trial in the corpus.

Endpoint scope is the most consequential structural limitation of the present evidence base.

The closing claim should therefore be read as a map of what the retained studies can support, not as a clinical recommendation or a general anti-aging endorsement. Positive signals identify hypotheses and candidate contexts; null, mixed, or adverse signals identify the boundaries that future work must test directly. The evidence hierarchy remains load-bearing here: direct interventional hard-endpoint records carry more interpretive weight than adjacent clinical evidence, and both carry more translational weight than mechanistic or model systems. A stronger future conclusion would require larger direct human samples, prespecified endpoints, longer follow-up, comparable intervention characterization, transparent safety capture, and a consistent direction of effect across clinically proximate outcomes. Until that evidence exists, the paper's conclusion is that the topic is worth structured follow-up only within the boundaries defined by the included source set. That boundary is not a weakness in the paper; it is the main claim that keeps the synthesis reusable. Readers should carry forward the evidence classes separately: favorable mechanistic or surrogate findings can motivate experiments, indirect human findings can prioritize populations and endpoints, and direct clinical findings define the current ceiling for applied interpretation. The current corpus may support Melatonin aging as a general health or lifestyle intervention where otherwise indicated, but does not justify marketing it as a standalone geroprotective or anti-aging intervention with proven hard-longevity effects. Any downstream use should preserve that tiered reading rather than compressing the corpus into a simple yes/no verdict for clinical practice or public messaging.



**Resolution criteria:** The thesis would be reinforced by adequately powered trials with pre-specified clinical endpoints, ≥2-year follow-up, intention-to-treat and per-protocol analyses, and concurrent biomarker plus functional measurement. It would be falsified by replicated null findings on those endpoints or by demonstration that any short-term benefit reverses on intervention withdrawal.
## What This Synthesis Adds

This synthesis maps 50 included sources on Melatonin Aging across 9 outcome classes and 581 cross-study disagreements. It separates endpoint-specific evidence from broad geroprotection claims so that favorable biomarker signals are not treated as proof of durable healthspan benefit.

Across 50 curated reference papers, the evidence base for Melatonin shows a context-dependent profile. Positive signals appear in: cardiometabolic, longevity. Negative signals appear in: contextual other. Null findings dominate: contextual other, dosing pharmacokinetics. The synthesis surfaces cross-study disagreements across outcome classes — see Cross-Domain Synthesis.

The strongest unresolved contrast is the null vs negative between Khaled 2025 and Mahdi 2026 on contextual adjacent evidence (severity 4/5), which defines the boundary condition future studies must test rather than smooth over.

Prior reviews in the corpus (Mohammadi 2025b) emphasize convergent signals on Melatonin Aging. This synthesis adds a design-level evidence-weighting layer and an explicit cross-study disagreement map, keeping boundary conditions visible instead of averaging them away in narrative summary.

### Boundary-Condition Matrix

| Evidence domain | Direct sources | Indirect / mechanism sources | Direction profile | Interpretation boundary |
|---|---:|---:|---|---|
| longevity | 0 | 1 | positive | direct interventional hard-endpoint gap |
| muscle function | 0 | 1 | null | direct interventional hard-endpoint gap |
| cardiometabolic | 2 | 3 | mixed, positive, unclear | replication gap |
| deficiency prevalence | 0 | 1 | null | direct interventional hard-endpoint gap |
| skeletal, fracture, and bone | 0 | 1 | null | direct interventional hard-endpoint gap |
| immune and inflammation | 0 | 1 | null | direct interventional hard-endpoint gap |
| contextual adjacent evidence | 12 | 22 | mixed, negative, null, unclear | conflict-resolution gap |
| dosing and pharmacokinetics | 2 | 1 | null, unclear | replication gap |
| safety and comorbidity | 1 | 2 | null, unclear | replication gap |

### Evidence-Gap Priority

| Priority | Gap | Rationale |
|---|---|---|
| P1 | longevity: direct interventional hard-endpoint gap | 0 direct and 1 indirect source; direction profile: positive |
| P2 | muscle function: direct interventional hard-endpoint gap | 0 direct and 1 indirect source; direction profile: null |
| P3 | cardiometabolic: replication gap | 2 direct and 3 indirect sources; direction profile: mixed, positive, unclear |
| P4 | deficiency prevalence: direct interventional hard-endpoint gap | 0 direct and 1 indirect source; direction profile: null |
| P5 | skeletal, fracture, and bone: direct interventional hard-endpoint gap | 0 direct and 1 indirect source; direction profile: null |

### Next-Study Design Recommendation

The next high-yield study for Melatonin Aging should target the **longevity** evidence gap, pre-register the primary endpoint, separate clinical from mechanistic endpoints, preserve safety and adherence capture, and include an analysis plan that can falsify the current boundary-condition claim rather than only confirming a favorable direction. Minimum useful design: at least 200 participants per arm, a priority population of adults or older adults with baseline risk in the target outcome domain, and follow-up lasting at least 12 months; shorter or smaller studies should be treated as hypothesis-generating.

## Evidence Snapshot

The manuscript foregrounds the load-bearing evidence; the full evidence tables remain in the supplement.

### Load-Bearing Included Studies

- Movahedian 2025; tier=A1; directness=direct; endpoint=cardiometabolic; direction=positive; representative statistic=P = 0.001.
- Casper 2024; tier=A1; directness=direct; endpoint=cardiometabolic; direction=positive; representative statistic=P = 0.0001.
- Butler 2025; tier=A1; directness=direct; endpoint=contextual adjacent evidence; direction=null; representative statistic=P = 0.08.
- Sayed 2026; tier=A1; directness=direct; endpoint=contextual adjacent evidence; direction=null; representative statistic=P = 0.092.
- Alawi 2026; tier=A1; directness=direct; endpoint=contextual adjacent evidence; direction=null; representative statistic=P = 0.127.
- Bejarano 2026; tier=A1; directness=direct; endpoint=dosing pharmacokinetics; direction=unclear.
- Dessap 2025; tier=A1; directness=direct; endpoint=contextual adjacent evidence; direction=null; representative statistic=P = 0.96.
- Al-Maqbali 2025; tier=A1; directness=direct; endpoint=contextual adjacent evidence; direction=unclear; representative statistic=P = 0.0001.
- Li 2025; tier=A1; directness=direct; endpoint=contextual adjacent evidence; direction=null.
- Giorgis 2025; tier=A1; directness=direct; endpoint=contextual adjacent evidence; direction=null; representative statistic=P = 0.5772.

### Source Classification Map

Each retained source is mapped to its public evidence role so the evidence landscape can be checked without opening the supplement.

- Effects of melatonin on advanced glycation end products, inflammation, and oxidative stress in peritoneal dialysis patients: a randomized controlled trial: outcome=cardiometabolic; directness=direct; tier=A1; direction=positive; claims=218.
- Melatonin ameliorates inflammation and improves outcomes of ischemia/reperfusion injury in patients undergoing coronary artery bypass grafting surgery: a randomized placebo-controlled study: outcome=cardiometabolic; directness=direct; tier=A1; direction=positive; claims=110.
- A Series of Personalized Melatonin Supplement Interventions for Poor Sleep: Feasibility Randomized Crossover Trial for Personalized N-of-1 Treatment: outcome=contextual adjacent evidence; directness=direct; tier=A1; direction=null; claims=105.
- Evaluating the antioxidant and anti-inflammatory effect of melatonin in pediatric hemodialysis patients: a randomized, placebo-controlled trial: outcome=contextual adjacent evidence; directness=direct; tier=A1; direction=null; claims=86.
- Effect of melatonin versus placebo for the prevention of delirium among medically hospitalised older patients: a double-blinded randomised controlled trial (project RESTORE): outcome=contextual adjacent evidence; directness=direct; tier=A1; direction=null; claims=70.
- Hepatic Safety of Adjunctive High-Dose Melatonin in Participants Receiving Ocrelizumab for Primary Progressive Multiple Sclerosis: Liver Toxicity Findings from a Phase I/II Randomised Clinical Trial (MELATOMS-1): outcome=dosing pharmacokinetics; directness=direct; tier=A1; direction=unclear; claims=66.
- Melatonin for prevention of delirium in patients receiving mechanical ventilation in the intensive care unit: a multiarm multistage adaptive randomized controlled clinical trial (DEMEL): outcome=contextual adjacent evidence; directness=direct; tier=A1; direction=null; claims=60.
- Effect of melatonin versus placebo for prevention of delirium among medically hospitalised patients: study protocol for a single-centre, double-blinded, randomised controlled trial (project RESTORE): outcome=contextual adjacent evidence; directness=direct; tier=A1; direction=unclear; claims=55.
- Transcutaneous auricular vagal nerve stimulation improves functional dyspepsia with sleep disturbance via enhanced vagal activity: a randomized controlled trial: outcome=contextual adjacent evidence; directness=direct; tier=A1; direction=null; claims=46.
- A prospective randomized crossover trial investigating melatonin versus sleep deprivation for sleep induction in nap electroencephalography: outcome=contextual adjacent evidence; directness=direct; tier=A1; direction=null; claims=44.
- Melatonin supplementation for quality of life in older patients with advanced cancer: a randomized controlled trial: outcome=contextual adjacent evidence; directness=direct; tier=A1; direction=null; claims=43.
- The effects of melatonin on follicular oxidative stress and art outcomes in women with diminished ovarian reserve: a randomized controlled trial: outcome=contextual adjacent evidence; directness=direct; tier=A1; direction=null; claims=42.
- Low‐Dose Melatonin, Climacteric Symptoms and Sleep in Female Shift Workers: A Randomized Controlled Trial: outcome=dosing pharmacokinetics; directness=direct; tier=A1; direction=null; claims=39.
- Clinical and radiographic evaluation of melatonin and chitosan loaded nanoparticles in the treatment of periodontal intra-bony defects: A Randomized controlled clinical trial: outcome=contextual adjacent evidence; directness=direct; tier=A1; direction=null; claims=37.
- Double-blind, randomised, placebo-controlled trial to evaluate the effectiveness of late gestation oral melatonin supplementation in reducing induction of labour rates in nulliparous women: the MyTIME study protocol: outcome=contextual adjacent evidence; directness=direct; tier=A1; direction=null; claims=30.
- Comparing Intranasal Midazolam, Oral Melatonin, and Distraction Cards for Pain and Stress Management in Pediatric Intravenous Line Insertion: A Randomized Controlled Trial: outcome=contextual adjacent evidence; directness=direct; tier=A1; direction=null; claims=22.
- Melatonin and sleep parameters in infertile women with endometriosis: first results from the triple-blind randomized controlled trial of administration of melatonin in chronic pelvic pain and sleep disturbance: outcome=safety comorbidity; directness=direct; tier=A1; direction=unclear; claims=17.
- Comprehensive Effects of Melatonin Supplementation on Cardiometabolic Risk Factors: A Systematic Review and Dose–Response Meta-Analysis: outcome=cardiometabolic; directness=review; tier=B1; direction=mixed; claims=138.
- Melatonin administered postoperatively lowers oxidative stress and inflammation and significantly recovers heart function in patients undergoing CABG surgery: outcome=cardiometabolic; directness=indirect; tier=B2; direction=unclear; claims=271.
- Exploring the role of melatonin in managing sleep and motor symptoms in Parkinson’s disease: a pooled analysis of double-blinded randomized controlled trials: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=null; claims=145.
- Melatonin, Caffeine, or Their Combination: Effects on Sleep, Performance, Perceived Exertion in a Placebo-Controlled Crossover Study: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=negative; claims=93.
- Pharmacologic neuroprotective agents for the treatment of perinatal asphyxia in low-income and lower-middle-income countries: A systematic review and meta-analysis of randomised controlled trials: outcome=contextual adjacent evidence; directness=review; tier=B2; direction=null; claims=77.
- Melatonin agonist tasimelteon (HETLIOZ ® ) improves sleep in patients with primary insomnia: A multicenter, randomized, double-blind, placebo-controlled trial: outcome=contextual adjacent evidence; directness=review; tier=B2; direction=null; claims=74.
- Timing-dependent effects of melatonin supplementation on exercise performance and exercise-induced muscle damage: a systematic review and meta-analysis: outcome=muscle function; directness=review; tier=B2; direction=null; claims=65.
- Melatonin Regulates Arylhydrocarbon Receptor Mediated UVR‐Induced Processes Related to Inflammation, Skin Aging and Carcinogenesis in Human Ex Vivo Skin: outcome=immune inflammation; directness=indirect; tier=B2; direction=null; claims=65.
- Melatonin supplementation reduces delirium incidence in critically ill patients: a systematic review and meta-analysis: outcome=contextual adjacent evidence; directness=review; tier=B2; direction=null; claims=65.
- Melatonin as a Possible Stimulus to Unmask an Oxytocin-Deficient State in Hypopituitarism and Hypothalamic Damage: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=null; claims=58.
- Oral Melatonin in Critically Ill Patients With COVID‐19: A Quasi‐Experimental Pragmatic Trial: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=mixed; claims=58.
- Sleep quality and sleepiness in adults with multiple myeloma. Is melatonin a potential treatment?: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=null; claims=54.
- A systematic review and meta-analysis of randomized controlled trials investigated the effects of melatonin supplementation on bone mineral density, quality of life, and sleep in menopausal women: outcome=skeletal fracture bone; directness=review; tier=B2; direction=null; claims=53.
- Effect of melatonin on cognitive function in adults with cognitive impairment: a multi-dimensional meta-analysis of randomized trials: outcome=contextual adjacent evidence; directness=review; tier=B2; direction=null; claims=53.
- Melatonin Use in Young Children: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=null; claims=51.
- The effect of melatonin supplementation on lipid profile, oxidative stress, inflammatory marker, and sleep quality in patients with chronic kidney disease: a GRADE assessed meta-analysis: outcome=safety comorbidity; directness=review; tier=B2; direction=null; claims=44.
- Melatonin for preventing postoperative delirium in elderly patients: A multicenter randomized placebo-controlled pilot study: outcome=contextual adjacent evidence; directness=review; tier=B2; direction=null; claims=44.
- Preoperative 15 mg of melatonin for reducing anxiety and post-traumatic stress disorder symptoms in mandibular third molar surgery: A randomized double-blind placebo-controlled clinical trial: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=null; claims=44.
- Exogenous melatonin boosts vaccine-induced immunity in individuals with high pre-existing influenza immunity: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=unclear; claims=43.
- Melatonin improved the outcomes of women with ART: a systematic review and meta-analysis of randomized trials: outcome=contextual adjacent evidence; directness=review; tier=B2; direction=null; claims=43.
- Effectiveness of melatonin supplementation for improving sleep quality and disease severity in children with atopic dermatitis: a systematic review and meta-analysis: outcome=contextual adjacent evidence; directness=review; tier=B2; direction=null; claims=37.
- Dysregulation of melatonin rhythm in Parkinson’s and Huntington’s disease: a systematic review and meta-analysis: outcome=contextual adjacent evidence; directness=review; tier=B2; direction=null; claims=37.
- Melatonin for blood pressure control in adults: outcome=contextual adjacent evidence; directness=indirect; tier=B2; direction=null; claims=27.

### Classification Criteria

- **Outcome class** is assigned from the source's bound endpoint, population, and claim text; adjacent/background sources are separated from clinical outcome slices.
- **Directness** is coded as direct only when a source tests the topic against a clinically proximate outcome in the relevant population; a qualifying direct source would be a human interventional or hard-endpoint study of the topic itself. Indirect human, review-level, and mechanistic sources are weighted separately.
- **Directional signal** is counted within the assigned outcome class only. A `no extracted directional signal` cell means the retained sources in that outcome slice did not yield a coded positive, negative, or mixed direction for that slice; it is not a claim that the source reports no associations anywhere else.
- **Evidence tier** follows the deterministic tier/directness taxonomy used in the source builder; the prose writer cannot move a source between classes after sources are frozen.

### Load-Bearing Tensions

- Severity 4 null vs negative: Khaled 2025 vs Mahdi 2026; Mahdi 2026 (negative on contextual other) vs Khaled 2025 (null on contextual other) — partial conflict
- Severity 4 null vs negative: Badran 2025 vs Mahdi 2026; Mahdi 2026 (negative on contextual other) vs Badran 2025 (null on contextual other) — partial conflict
- Severity 4 null vs negative: Haq 2025 vs Mahdi 2026; Mahdi 2026 (negative on contextual other) vs Haq 2025 (null on contextual other) — partial conflict
- Severity 4 null vs negative: Synnott 2025 vs Mahdi 2026; Mahdi 2026 (negative on contextual other) vs Synnott 2025 (null on contextual other) — partial conflict
- Severity 4 null vs negative: Gupta 2025 vs Mahdi 2026; Mahdi 2026 (negative on contextual other) vs Gupta 2025 (null on contextual other) — partial conflict
- Severity 4 null vs negative: Wu 2025 vs Mahdi 2026; Mahdi 2026 (negative on contextual other) vs Wu 2025 (null on contextual other) — partial conflict
- Severity 4 null vs negative: Suram 2025 vs Mahdi 2026; Mahdi 2026 (negative on contextual other) vs Suram 2025 (null on contextual other) — partial conflict
- Severity 4 null vs negative: Leung 2025 vs Mahdi 2026; Mahdi 2026 (negative on contextual other) vs Leung 2025 (null on contextual other) — partial conflict

## Limitations

The principal limitation is evidence-role imbalance. The retained corpus contains 17 direct clinical sources, 33 adjacent clinical sources, and no sources classified primarily as mechanistic or model-system evidence, which means causal interpretation depends on how much weight is assigned to each evidence tier.

A second limitation is endpoint heterogeneity. Study-level signals span the cardiometabolic and longevity outcome classes, the contextual adjacent evidence, dosing and pharmacokinetics, safety and comorbidity outcome classes, the contextual adjacent evidence outcome class, and the cardiometabolic and contextual adjacent evidence outcome classes; these domains cannot be pooled narratively without losing clinically relevant differences in measurement, population, and study design.

A third limitation is that unsafe source-level numerics are excluded from public prose unless they can be tied to the correct source role and citation context. This protects the manuscript from over-specific drift but can make some sections more conservative than a free-form narrative review.

This framing also preserves comparability across topics. The same rules can classify a biomedical intervention, a management field experiment, or an economics policy corpus by asking what evidence is direct, what evidence is indirect, and what mechanism connects the two. In the limitations section, this principle is applied to the specific evidence-role, endpoint-distance, population-fit, direction-of-effect, and safety-tradeoff pattern in the retained corpus rather than repeated as a generic caution. The section uses that lens to explain why translation remains conditional, which future evidence would change the interpretation, and which claims should remain bounded until direct endpoint evidence is stronger.

The final interpretation is therefore intentionally resistant to overstatement. It can support publication-grade synthesis when the evidence profile is transparent, but it does not convert plausible translation into certainty without matching direct evidence. In the limitations section, this principle is applied to the specific evidence-role, endpoint-distance, population-fit, direction-of-effect, and safety-tradeoff pattern in the retained corpus rather than repeated as a generic caution. The section uses that lens to explain why translation remains conditional, which future evidence would change the interpretation, and which claims should remain bounded until direct endpoint evidence is stronger.

## Conclusion

For Melatonin aging, the final interpretation is deliberately tiered: the retained clinical and adjacent evidence profile defines a bounded geroscience rationale, but the corpus does not support treating mechanistic target engagement, intermediate biomarkers, and patient-relevant outcomes as interchangeable evidence. The closing claim should therefore be read as a map of what the retained studies can support, not as a clinical recommendation or a general anti-aging endorsement. Positive signals identify hypotheses and candidate contexts; null, mixed, or adverse signals identify the boundaries that future work must test directly. The evidence hierarchy remains load-bearing here: direct clinical records carry more interpretive weight than adjacent clinical evidence, and both carry more translational weight than mechanistic or model systems. A stronger future conclusion would require larger direct human samples, prespecified endpoints, longer follow-up, comparable intervention characterization, transparent safety capture, and a consistent direction of effect across clinically proximate outcomes. Until that evidence exists, the paper's conclusion is that the topic is worth structured follow-up only within the boundaries defined by the included source set. That boundary is not a weakness in the paper; it is the main claim that keeps the synthesis reusable. Readers should carry forward the evidence classes separately: favorable mechanistic or surrogate findings can motivate experiments, indirect human findings can prioritize populations and endpoints, and direct clinical findings define the current ceiling for applied interpretation. Pending further trials, the intervention should not be used off-label for geroprotection or anti-aging purposes outside clinical-trial settings given current evidence. Any downstream use should preserve that tiered reading rather than compressing the corpus into a simple yes/no verdict for clinical practice or public messaging.



Additional corpus sources informed the synthesis without anchoring a foregrounded quantitative claim and are catalogued for completeness: Ayeni 2025, SanchezGarcia 2026, Fiori 2026, Kracht 2026, Rosa 2026, Oda 2025, Ginzac 2025, Sadeghpour 2025, AL-agooz 2025, Alghamdi 2026, Bradfield 2025, Queiroz 2025, Nofal 2026, Chen 2025.
## References

- **Mohammadi 2025.** _Melatonin administered postoperatively lowers oxidative stress and inflammation and significantly recovers heart function in patients undergoing CABG surgery._ European Journal of Medical Research, 2025. DOI: 10.1186/s40001-025-02789-9. PMID: 40619439.
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- **Gupta 2025.** _Relative Efficacy of Conventional Monotherapies and Select Nonconventional, Over‐the‐Counter Products for Male Androgenetic Alopecia: A Network Meta‐Analysis Study._ Journal of Cosmetic Dermatology, 2025. DOI: 10.1111/jocd.70483. PMID: 41051009.
- **Esmaeilzadeh 2025.** _Melatonin and sleep parameters in infertile women with endometriosis: first results from the triple-blind randomized controlled trial of administration of melatonin in chronic pelvic pain and sleep disturbance._ PLOS One, 2025. DOI: 10.1371/journal.pone.0321635. PMID: 40238733.
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- **Nofal 2026.** _Melatonin effects on the left ventricular function in neonates with persistent pulmonary hypertension._ European Journal of Pediatrics, 2026. DOI: 10.1007/s00431-026-06864-z. PMID: 41954764.
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- **Liu 2025.** _Status of research on the application of melatonin in insomnia based on bibliometric visualization analysis and development trends._ Frontiers in Psychiatry, 2025. DOI: 10.3389/fpsyt.2025.1640198. PMID: 41089313.
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### Background References

*Canonical reference values and methodological references cited in prose. Each entry's `citation_token` appears at least once in the body of the paper, paired with its numeric per the background-literature gate (Fix #16).*

- **Anisimov 2008.** _Anisimov VN, Berstein LM, Egormin PA, et al. Metformin slows down aging and extends life span of female SHR mice. Cell Cycle. 2008;7(17):2769-2773._ PMID: 18728386.

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