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In previous studies, we found that many totally blind people have free-running melatonin rhythms, but that free-running melatonin rhythms were not necessarily associated with periodic insomnia and daytime sleepiness. Thus, it was not clear if the circadian sleep propensity rhythm was free-running with the other circadian rhythms. In the present study, we report that the sleep propensity rhythm (as defined by an ultrashort sleep-wake schedule) free-ran with the melatonin, temperature and cortisol rhythms in a 44-year-old totally blind man even though he maintained a conventional sleep schedule and did not complain of clinically significant insomnia or excessive daytime sleepiness.
Nakagawa et al. (Wed,) studied this question.