Entrainment of free-running circadian rhythms by melatonin in blind people

Robert Sack, Richard W. Brandes, Adam R. Kendall, Alfred Lewy

Research output: Contribution to journalArticle

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Background: Most totally blind people have circadian rhythms that are 'free-running' (i.e., that are not synchronized to environmental time cues and that oscillate on a cycle slightly longer than 24 hours). This condition causes recurrent insomnia and daytime sleepiness when the rhythms drift out of phase with the normal 24-hour cycle. We investigated whether a daily dose of melatonin could entrain their circadian rhythms to a normal 24-hour cycle. Methods: We performed a crossover study involving seven totally blind subjects who had free-running circadian rhythms. The subjects were given 10 mg of melatonin or placebo daily, one hour before their preferred bedtime, for three to nine weeks. They were then given the other treatment. The timing of the production of endogenous melatonin was measured as a marker of the circadian time (phase), and sleep was monitored by polysomnography. Results: At base line, the subjects had free-running circadian rhythms with distinct and predictable cycles averaging 24.5 hours (range, 24.2 to 24.9). These rhythms were unaffected by the administration of placebo. In six of the seven subjects the rhythm was entrained to a 24.0-hour cycle during melatonin treatment (P

Original languageEnglish (US)
Pages (from-to)1070-1077
Number of pages8
JournalNew England Journal of Medicine
Issue number15
Publication statusPublished - Oct 12 2000


ASJC Scopus subject areas

  • Medicine(all)

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