Urinary 6-sulfatoxymelatonin excretion and aging: new results and a critical review of the literature.
Level 4 - case-series / case-control
Cross-sectional observational study and literature re-analysis
PubMed 10551768 · doi:10.1111/j.1600-079x.1999.tb00617.x
What was done
The authors measured urinary 6-sulfatoxymelatonin excretion in 253 subjects aged 21 to 82 years, analyzing age patterns with correlation and ANOVA across 5-year age spans. They also re-evaluated published data from 7 studies across wide age ranges, 11 studies comparing young versus older subjects, and 144 normal subject groups from 137 publications.
What was found
In the primary cohort of 253 subjects, 6-sulfatoxymelatonin excretion correlated inversely with age (r = -0.24, P < 0.05), with the oldest subjects excreting 36% less than the youngest. However, post hoc ANOVA indicated no significant decline after 25 years of age. Re-analysis of prior studies showed age-related changes were essentially complete before age 30. In the 137-publication dataset, plasma melatonin showed no significant difference between groups after 35 years of age, with the oldest groups having levels 43% of the youngest groups.
Why it matters
This paper challenges the assumption of a steady, lifelong decline in melatonin secretion, indicating that the reduction occurs early in adult life (between ages 20 and 30) and remains relatively stable thereafter.
Limits
The study is cross-sectional rather than a longitudinal follow-up, preventing assessment of individual trajectories. The abstract does not detail participant health status, kidney function, medication use, or assay standardization across the reviewed publications.
Cited by
- contradicts Pineal gland melatonin secretion begins to decline precipitously around age 40.