Open AccessBright Light During Wakefulness Improves Sleep Quality in Healthy Men: A Forced Desynchrony Study Under Dim and Bright Light (III)
Author(s) -
Renske Lok,
Tom Woelders,
Marijke C. M. Gordijn,
Minke J. van Koningsveld,
Klaske Oberman,
Sebastiaan Fuhler,
Domien Beersma,
Roelof A. Hut
Publication year - 2022
Publication title -
journal of biological rhythms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.484
H-Index - 101
eISSN - 1552-4531
pISSN - 0748-7304
DOI - 10.1177/07487304221096910
Subject(s) - wakefulness , circadian rhythm , non rapid eye movement sleep , free running sleep , sleep (system call) , psychology , audiology , anesthesia , medicine , eye movement , electroencephalography , neuroscience , circadian clock , light effects on circadian rhythm , computer science , operating system
Under real-life conditions, increased light exposure during wakefulness seems associated with improved sleep quality, quantified as reduced time awake during bed time, increased time spent in non-rapid eye movement (NREM) sleep, or increased power of the electroencephalogram delta band (0.5-4 Hz). The causality of these important relationships and their dependency on circadian phase and/or time awake has not been studied in depth. To disentangle possible circadian and homeostatic interactions, we employed a forced desynchrony protocol under dim light (6 lux) and under bright light (1300 lux) during wakefulness. Our protocol consisted of a fast cycling sleep-wake schedule (13 h wakefulness-5 h sleep; 4 cycles), followed by 3 h recovery sleep in a within-subject cross-over design. Individuals (8 men) were equipped with 10 polysomnography electrodes. Subjective sleep quality was measured immediately after wakening with a questionnaire. Results indicated that circadian variation in delta power was only detected under dim light. Circadian variation in time in rapid eye movement (REM) sleep and wakefulness were uninfluenced by light. Prior light exposure increased accumulation of delta power and time in NREM sleep, while it decreased wakefulness, especially during the circadian wake phase (biological day). Subjective sleep quality scores showed that participants rated their sleep quality better after bright light exposure while sleeping when the circadian system promoted wakefulness. These results suggest that high environmental light intensity either increases sleep pressure buildup during wakefulness or prevents the occurrence of micro-sleep, leading to improved quality of subsequent sleep.