Sleep/wake cycles in the dark: sleep recorded by polysomnography in 26 totally blind subjects compared to controls

Objectives: To evaluate subjective sleep difficulties and nocturnal sleep with polysomnography in 26 completely blind subjects, living in normal social environments and to compare the findings with those of matched controls. Methods: Twenty-six blind individuals with no light perception and free-running melatonin rhythms, as assessed by measurements of urinary and salivary 6-sulfatoxymelatonin, were polygraphically monitored. Actigraphy and Braille sleep logs were obtained from the individuals for 14 days. Their sleep was compared to that of matched controls. Results: Blind individuals were ‘free-running’ despite normal and regular social interaction. Each had ordinary working conditions and/or a family life with seeing spouse and children. Actigraphy obtained on 14 successive days showed the presence of small amount of daytime ‘sleep’ – 24.7±25.1 min per day. Total sleep time, sleep latency, sleep efficiency, and total REM sleep were significantly lower than in matched controls. Working blind subjects had a slightly higher total sleep time than those retired and unemployed. Congenital blindness, acquired blindness, presence of bilateral prosthetic eyes or presence of normal human eyes did not produce different nocturnal sleep and ‘free-running’ pattern results. Conclusions: Reduced total sleep time and other sleep abnormalities were associated with the complaint of daytime sleepiness and poor sleep in blind subjects. The abnormalities of sleep, which may be related to the free-running condition, present an additional challenge for these subjects, who are already severely impaired by their complete lack of vision.