Sleep laboratory investigations on hypnotic properties of melatonin

Melatonin (MLT), a pineal hormone, has some sedative and hypnotic properties. To explore this effect further 20 young, healthy volunteers exposed to artificial insomnia participated in a double-blind, placebo controlled, parallel group design study. They slept in a sleep laboratory for several consecutive nights and were polygraphically monitored and subjected to a battery of psychometric tests and standardized self-report questionnaires each morning. One night all subjects received only placebo (21:00 hours) and on a second night half of them were subjected to placebo and half to MLT. On the later night blood MLT levels were measured. Polygraphic recordings revealed that MLT at bedtime decreased the time the subjects were awake before sleep onset (P less than 0.025), sleep latency (P less than 0.05), and the number of awakenings during the total sleep period (P less than 0.025), and increased sleep efficiency (P less than 0.05). In addition, it decreased sleep stage 1 (P less than 0.05) and increased sleep stage 2 (P less than 0.025). On the morning following the treatment most objective and subjective measures for awakening quality showed a trend towards improvement after MLT. One hour after its oral administration, serum MLT rose to a high pharmacological level (25817 pg/ml; median), but individual peak serum MLT levels varied by a factor of 300.(ABSTRACT TRUNCATED AT 250 WORDS)