Do plasma melatonin concentrations decline with age?

PURPOSE: Numerous reports that secretion of the putative sleep-promoting ho rmone melatonin declines with age have led to suggestions that melatonin re placement therapy be used to treat sleep problems in older patients. We sou ght to reassess whether the endogenous circadian rhythm of plasma melatonin concentration changes with age in healthy drug-free adults. METHODS: We analyzed the amplitude of plasma melatonin profiles during a co nstant routine in 34 healthy drug-free older subjects (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). RESULTS: We could detect no significant difference between a healthy and dr ug-free group of older men and women as compared to one of young men in the endogenous circadian amplitude of the plasma melatonin rhythm, as describe d by mean 24-hour average melatonin concentration (70 pmol/liter vs 73 pmol /liter, P = 0.97), or the duration (9.3 hours vs 9.1 hours, P = 0.43), mean (162 pmol/liter vs 161 pmol/liter, P = 0.63), or integrated area (85,800 p mol x min/liter vs 86,700 pmol x min/liter, P = 0.66) of the nocturnal peak of plasma melatonin. CONCLUSION: These results do not support the hypothesis that reduction of p lasma melatonin concentration is a general characteristic of healthy aging. Should melatonin replacement therapy or melatonin supplementation prove to be clinically useful, we recommend that an assessment of endogenous melato nin be carried out before such treatment is used in older patients. Am J Me d. 1999;107:432-436. (C) 1999 by Excerpta Medica, Inc.