Physiological melatonin levels in healthy older people: A systematic review.
Level 3 - non-randomized controlled study
Systematic review of observational and cross-sectional physiological studies
PubMed 27302542 · doi:10.1016/j.jpsychores.2016.05.005
What was done
A systematic review of literature from PubMed and Embase (published January 1, 1980 to October 5, 2015) evaluating physiological melatonin levels and secretion patterns in healthy individuals aged ≥65 years.
What was found
Nineteen studies were included, with sample sizes between 5 and 60 participants per study. Most measured melatonin using radioimmunoassay, with 1 to 96 measurements per 24 hours. Sixteen studies showed a clear nocturnal secretion peak (mostly at 02:00h or 03:00h). Maximum concentrations ranged widely from 11.2 to 91.3 pg/ml. The maximum melatonin level was 49.3 pg/ml in studies with a mean participant age of 65–70 years versus 27.8 pg/ml in studies with a mean age ≥75 years (p < 0.001). Total 24-hour production appeared unchanged in healthy aging, but maximal nocturnal peak concentration declined.
Why it matters
It clarifies that healthy aging is associated with a blunted nocturnal peak rather than a complete loss of 24-hour melatonin production, providing physiological context for dosing melatonin in older populations.
Limits
The review relies on small primary studies (n = 5–60) with substantial methodological heterogeneity in sampling frequency (1 to 96 times per 24 hours) and assay protocols. Findings reflect cross-sectional study comparisons rather than longitudinal intra-individual trajectories.
Cited by
- supports Aging leads to a natural decline in endogenous melatonin production.