Do plasma melatonin concentrations decline with age?
Level 4 - case-series / case-control
Cross-sectional comparative physiological study comparing two age cohorts
PubMed 10569297 · doi:10.1016/s0002-9343(99)00266-1
What was done
Researchers evaluated plasma melatonin profiles under a constant routine protocol in 34 healthy, drug-free older adults (20 women and 14 men, aged 65 to 81 years) and compared them with 98 healthy, drug-free young men (aged 18 to 30 years) to assess whether endogenous circadian melatonin concentrations change with age.
What was found
No statistically significant differences were found between healthy older subjects and young men in 24-hour average melatonin concentration (70 pmol/L vs 73 pmol/L, P = 0.97), nocturnal peak duration (9.3 hours vs 9.1 hours, P = 0.43), nocturnal peak mean (162 pmol/L vs 161 pmol/L, P = 0.63), or integrated nocturnal area (85,800 pmol x min/L vs 86,700 pmol x min/L, P = 0.66).
Why it matters
This study challenges the common assumption that melatonin secretion inevitably declines with healthy aging, suggesting that age alone should not justify melatonin replacement therapy without documented deficiency.
Limits
The comparison group of young subjects consisted entirely of men, creating a sex imbalance against the mixed-sex older group. The design was cross-sectional rather than longitudinal, the older sample size was modest (n = 34), and the strict exclusion of disease or medication limits generalizability to typical older populations.
Cited by
- contradicts Endogenous melatonin production in the human body begins to decline around age 50.