Circadian activity–rest and sleep–wake rhythms in blind adolescents and adults

Abstract

Although light is accepted as the dominant zeitgeber for entrainment of the human circadian system, reports that some totally blind individuals appear entrained to the 24-h day have suggested that non-photic stimuli may also be effective circadian synchronizers in humans. We investigated the sleep and rest–activity patterns of 22 blind subjects (17 teenagers and 5 adults) in their natural environmental conditions. Sleep disorder was assessed using three questionnaires and daily activity was monitored using the actiwatch activity monitoring system. Blind adults showed a significantly decreased “actual sleep time” and “sleep efficiency”. In the blind adult and control adult groups the actigraphic estimates of “sleep latency” and “fragmentation index” increased significantly. The interdaily stability was similar in the four age groups, while blind and control adults showed a significant decrease in relative amplitude. The present study suggests that age might have more effects in the alteration of sleep–wake, activity–rest rhythms than blindness.

Keywords:

• blind
• sleep disorder
• entrainment
• actigraphy
• non-photic stimuli