Effects on subjective and objective alertness and sleep in response to evening light exposure in older subjects

Jun 14, 2011Behavioural brain research

How Evening Light Affects Feelings of Alertness, Measured Alertness, and Sleep in Older Adults

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Abstract

Evening light exposure significantly increased subjective alertness and altered sleep patterns in older adults.

Ten healthy older adults with sleep complaints participated in a 13-day study.
Circadian phase assessments showed shifts after exposure to evening light.
Subjective alertness and wake brain activity were significantly higher during light exposures compared to pre-exposure levels.
Evening light exposure prolonged the time it took to enter REM sleep.
Increased wake brain activity was negatively correlated with the duration of REM sleep.
Evening light exposure may help older adults with early evening sleepiness without harming subsequent sleep quality.

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Evening bright light exposure is reported to ameliorate daytime sleepiness and age-related sleep complaints, and also delays the timing of circadian rhythms. We tested whether evening light exposure given to older adults with sleep-wake complaints would delay the timing of their circadian rhythms with respect to their sleep timing, thereby reducing evening sleepiness and improving subsequent sleep quality. We examined the impact of evening light exposure from two different light sources on subjective alertness, EEG activity during wakefulness, and sleep stages. Ten healthy older adults with sleep complaints (mean age=63.3 years; 6F) participated in a 13-day study. After three baseline days, circadian phase was assessed. On the evening of days 5-8 the subjects were exposed for 2h to either polychromatic blue-enriched white light or standard white fluorescent light, and on the following day circadian phase was re-assessed. Subjects were allowed to leave the laboratory during all but the two days when the circadian phase assessment took place. Evening assessments of subjective alertness, and wake and sleep EEG data were analyzed. Subjective alertness and wake EEG activity in the alpha range (9.75-11.25 Hz) were significantly higher during light exposures when compared to the pre-light exposure evening (p<0.05). The light exposures produced circadian phase shifts and significantly prolonged latency to rapid eye-movement (REM) sleep for both light groups (p<0.05). The increase in wake EEG alpha activity during the light exposures was negatively correlated with REM sleep duration (p<0.05). Evening light exposure could benefit older adults with early evening sleepiness, without negatively impacting the subsequent sleep episode.

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Effects on subjective and objective alertness and sleep in response to evening light exposure in older subjects

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