Treatment of
circadian rhythm disorders, whether precipitated by intrinsic factors (e.g.,
sleep disorders,
blindness,
mental disorders, aging) or by extrinsic factors (e.g., shift work,
jet-lag) has led to the development of a new type of agents called 'chronobiotics', among which
melatonin is the prototype. The term 'chronobiotic' defines as a substance capable of shifting the phase of the circadian time system thus re-entraining circadian rhythms.
Melatonin administration synchronizes the sleep-wake cycle in blind people and in individuals suffering from
delayed sleep phase syndrome or
jet lag, as well in shift-workers. The effect of
melatonin on sleep is probably the consequence of increasing sleep propensity (by inducing a fall in body temperature) and of a synchronizing effect on the circadian clock (chronobiotic effect). We successfully employed the timely use of three factors (
melatonin treatment, exposure to light, physical exercise) to hasten the resynchronization after transmeridian flights comprising 12-13 time zones, from an average of 8-10 days to about 2 days. Daily
melatonin production decreases with age, and in several pathologies, attaining its lowest values in Alzheimer's
dementia patients. About 45% of
dementia patients have severe disruptions in their sleep-wakefulness cycle. Both in aged subjects having very minimal
sleep disorders as well as in demented patients with a very severe disorganization of the sleep-wake cycle,
melatonin treatment reduced the variability of sleep onset and restored sleep.