Sleepy concern
melatonin, considered a miracle hormone that banishes illness and reverses ageing has attracted the attention of the public health policy makers in the us. A meeting on melatonin at the National Institute of Health, Bethesda, called for a multicentre clinical trial to determine melatonin's efficacy and safety ( jama , Vol 276).
Melatonin, produced by the pineal gland in the brain, also occurs naturally in some foods and is sold as dietary supplement. Wide media coverage on melatonin has created a us market of about $250-350 million a year.
Secreted during nights, melatonin provides a cue to diurnal and nocturnal species. For animals and birds, it also signals the time for migration, hibernation and reproductive cycles. Melatonin entrains 24 hour rhythm of the body functions controlled by the hypothalamus of brain, the body's master clock.
The meeting noted that the extraordinary consumption of this chemical indicates that sleep disorders are widespread. No medical catastrophe has been reported, yet physicians should prescribe only pharmacological and behavioural treatment for sleep complaints and caution against excessive dependence on the drug.
Albert Levy and his colleagues from the Sleep and Mood Disorders Laboratory at Oregon Health Sciences University (ohsu), Portland, have devised light treatment for numerous disorders of the biological clock.
Light and melatonin function complementarily in the 24 hour cycle. While light provides the daytime signal to the brain, melatonin provides night-time signal. A possible function of melatonin is to suppress the perception of light.
Often it becomes desirable to shift the biological clock like while travelling between continents. For the purpose of shifting the body clock earlier one could use melatonin. But during day time melatonin may induce sleepiness, lower body temperature and extend sleep.
Studies done over 10 years in England have shown that melatonin may be among the safest drugs at doses of five mg per day for not more than a week to cure sleep disorders. Robert Sack, a professor of psychiatry at the ohsu and working with Levy has found melatonin helpful in restoring normal sleep-wake cycle in blind people.
The use of melatonin in young people with sleep problems is causing concern. A 1995 survey estimated most us adults reached out for melatonin unconcerned with its negative impact.
As Gary Richardson of the Harvard Medical School clarifies: "We don't have the data to prescribe it, but because it's out there, in the market, we as physicians have to address it.' Some adverse effects reported include infertility, suppression of male sexual drive, hypothermia and retinal damage. Even product purity as a dietary supplement was a concern, but in the absence of firm evidence, it cannot even be banned.
The meet identified the agenda to develop a standard melatonin preparation, determine its relation to sleep, identify which populations benefit most and take up basic research on long term safety and efficacy