Alterations in the circadian rhythm of salivary melatonin begin during middle-age.
Level 4 - case-series / case-control
Cross-sectional observational study across age cohorts
PubMed 12485366 · doi:10.1034/j.1600-079x.2003.01897.x
What was done
Evaluated 24-hour salivary melatonin circadian rhythms in 52 healthy volunteers categorized into four age groups: young, middle-aged, old, and oldest. Saliva was collected at 12 time points over a 24-hour period for each participant, and circadian rhythmicity was analyzed using base cosine function curve fitting.
What was found
Significant 24-hour circadian rhythms were detected in 51 of 52 subjects. A stepwise decline in rhythm amplitude started in middle age (~40 years old), with middle-aged subjects displaying only 60% of the nocturnal peak amplitude of young subjects, alongside the longest peak duration and lowest daytime baseline levels. Old and oldest subjects exhibited diminished nocturnal peaks and elevated daytime baseline levels, with the oldest group showing offset melatonin levels more than two times higher than the other groups.
Why it matters
It indicates that pineal secretory decline and circadian alterations in free melatonin begin in middle age rather than emerging only in late senescence.
Limits
The study is cross-sectional rather than longitudinal. The sample is small (52 participants across four cohorts), and the abstract omits exact concentration values, age cutoffs, sex distribution, and control for light exposure.
Cited by
- supports Aging leads to a natural decline in endogenous melatonin production.