Daily melatonin intake resets circadian rhythms of a sighted man with non‐24‐hour sleep‐wake syndrome who lacks the nocturnal melatonin rise

Open Access
Publisher Website
Google Scholar
Abstract
Effects of daily melatonin intake on the circadian rhythms of sleep and wakefulness, rectal temperature and plasma cortisol were examined in a sighted man who had suffered from the non‐24‐hour sleep‐wake syndrome. The subject lacked the nocturnal melatonin rise in plasma, but showed robust circadian rhythms in rectal temperature and plasma cortisol. The sleep‐wake rhythm free‐ran with a period longer than 24 hours. Daily melatonin intake at 21:00 h concentrated sleep episodes in the nocturnal period (24:00–8:00 h), and increased the length of the episodes. A single oral dose (3 mg) of melatonin increased plasma melatonin levels to about 1300 pg/mL within one hour and remained at pharmacological levels for approximately 6 hours. The trough of rectal temperature and the circadian rise of plasma cortisol were fixed to the early morning. A higher dose of melatonin (6 mg) did not improve the general feature. After the cessation of melatonin intake, the sleep‐wake rhythm began to free‐run together with the circadian rhythms in rectal temperature and plasma cortisol. It is concluded that daily intake of melatonin at early night time resets the circadian rhythms in a sighted man who lacked the nocturnal melatonin rise and showed free‐running circadian rhythms in routine life.