Low Doses of Melatonin Promote Sleep Onset and Maintenance in Older People—An Update
Plasma melatonin levels in young adults are about 10-fold higher during the night than during daylight hours, and these high levels promote both the onset of sleep at bedtime and the speedy resumption of sleep after premature nocturnal awakenings. With aging, melatonins nocturnal secretion from the pineal gland declines, as do plasma melatonin levels, total sleep time, and sleep efficiency. A very small dose (0.3 mg) of melatonin is usually sufficient to restore nighttime plasma melatonin levels to those characteristic of young people, and to accelerate the resumption of sleep after premature awakenings. The much larger doses that are marketed can produce side effects that are not observed when the melatonin in the plasma derives solely from its secretion by the pineal. Very high doses may also desensitize melatonins receptors in the brain, subsequently diminishing melatonins efficacy in promoting sleep. This article updates an earlier summary (Richard J Wurtman, Use of melatonin to promote sleep in older people,US Neurology, 2012;8(1):101) of melatonins utility in promoting sleep among older people.