Melatonin (n-acetyl-5-methoxytryptamine) Is a Hormone Produced during the Hours of Darkness by the Pineal

MELATONIN (N-ACETYL-5-METHOXYTRYPTAMINE) IS A HORMONE PRODUCED DURING THE HOURS OF DARKNESS BY THE PINEAL GLAND. From very low daytime levels an increase in plasma melatonin occurs in the evening, peaking between 01:00-05:00h, and becoming barely detectable again by about 09:00-10:00h Secretion in many animals is truly photoperiodic, that is it is influenced by the length of the day/night cycles during the year. In humans this photoperiodicity may be partially distorted by artificial lighting1,2,3 but can be sustained in subjects maintained for long periods in artificial short or long days.4 Although plasma melatonin levels in older people are reported to be lower than younger people5,6,7,8 plasma levels vary widely in all ages. Some older people have relatively high levels of melatonin, others have significantly reduced levels, and a few have no evidence of melatonin secretion. The effects of reduced melatonin levels are still uncertain, as is the potential of melatonin supplementation. Studies in younger participants have demonstrated the efficacy of melatonin as a mild sedative and sleep-promoting agent using various doses, especially if administered during daytime10,11,12 although administration may13,14 or may not15,16 alter normal sleep. Melatonin administered to older people with sleep problems has shown conflicting results. Improvement in sleep quality has been reported particularly with controlled release melatonin17,18,19 but others suggest that only sleep latency (time from lights out to falling asleep) is reduced and sleep efficiency improved20,21. Age-related problems in sleeping are well described, and are more prevalent in women.22,23 For many, aging is associated with decreased total sleep time, increased sleep latency, and more awakenings particularly in the latter stages of the night (problems with sleep maintenance). Others have problems in sleeping for different reasons, for instance poor health, anxiety or depression, or a less than optimal environment. The object of this research was to investigate whether older people with age-related sleep problems do secrete significantly less melatonin than those who report normal sleep patterns. If this were the case, it would support the widespread but unproved belief that supplementary melatonin improves quality of sleep in this age group.