Lessons from the blind

Abstract

During the late 1970s, I saw the first blind patient on circadian rhythms [2] also concluded that “light does not have the capacity to affect parameters who came for consultation in the Technion sleep laboratory because of severe insomnia. He became of autonomous rhythms regularly when operating continuously” (p. 93). From the vantage point of blind following a war injury in 1948. His symptoms were unusual and different from those of most knowing that even ordinary room light may affect the circadian pacemaker in humans [3], some of insomniacs I had seen. This man mostly complained of severe sleep onset insomnia, but added that Aschoff and Wever observations in the time-free environment indeed hinted that light plays an imwhen he found it difficult to fall asleep at night, he could easily fall asleep during the day. His wife added portant role in circadian regulation. When they isolated some of their subjects in total darkness that he became accustomed to staying awake at night because “being blind, it was obvious that it throughout the study period, they had significantly shorter free-running rhythms than subjects isolated did not matter to him if it was day or night.” With the hindsight of what we know today about circadian under a variety of lighting conditions. In fact, they even studied blind subjects in the time-free ensleep disorders in the blind, most probably this blind person suffered from a free-running sleep– vironment and found that their free-running rhythms were similar to those of subjects inwake cycle. Unfortunately, my attempts to document what seemed to me at that time to be unusual vestigated in total darkness. Interestingly, as reported by Sack and Lewy, the free-running rhythms sleep disturbances, by asking his wife to keep a of blind people studied in their normal environment, sleep diary, were unsuccessful. In this issue of Sleep are similar to the rhythms of sighted subjects who Medicine Reviews, Sack and Lewy, whose fruitful were isolated in the Andech’s studies under various collaboration has produced many of the original lighting conditions. This points to the potential observations on sleep and circadian rhythms in importance of non-photic stimuli to the fine tuning the blind, comprehensively review the impact of of the circadian system. Investigating the sleep–wake blindness on sleep, and how sleep disorders in the cycles of blind people in isolated and non-isolated blind have helped to understand the regulation of conditions may provide useful information on this circadian rhythms in general. important issue. It is surprising how late the pervasive effect of Sack and Lewy conclude their paper by discussing light on the circadian clock was recognized. In 1975, the potential role of melatonin in the entrainment Aschoff et al. [1] who were the first to demonstrate of free-running blind people. Here, they relied on free-running rhythms, concluded that “An artificial their own impressive list of studies on the relight–dark cycle seems to be of little importance lationship between melatonin and circadian sleep– for the entrainment of human circadian rhythms in wake regulation, starting with the first otherwise constant conditions.” (p. 64). Likewise, demonstration of the suppressing effect of bright Wever, Aschoff’s long-time collaborator, in his book light on melatonin production in humans [4], and culminating in their recent description of entraining free-running blind people to the 24-h cycle by Correspondence should be addressed to: P. Lavie PhD. E-mail: plavie@tx.technion.ac.il timed melatonin administration [5]. The theoretical