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Behav Brain Res. 2018 Aug 1;348:267-275. doi: 10.1016/j.bbr.2018.04.021. Epub 2018 Apr 21.

Improved cognitive morning performance in healthy older adults following blue-enriched light exposure on the previous evening.

Author information

1
Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA, United States; Division of Sleep Medicine, Harvard Medical School, Boston, MA, United States; Wits Sleep Laboratory, Brain Function Research Group, School of Physiology, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa. Electronic address: karine.scheuermaier@wits.ac.za.
2
Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA, United States; Division of Sleep Medicine, Harvard Medical School, Boston, MA, United States; Sleep research and clinical chronobiology, Institute of Physiology, Charité Universitätsmedizin, Berlin, Germany; Clinic for Sleep and Chronomedicine, St. Hedwig-Krankenhaus, Berlin, Germany.
3
Division of Sleep and Circadian Disorders, Brigham and Women's Hospital, Boston, MA, United States; Division of Sleep Medicine, Harvard Medical School, Boston, MA, United States.

Abstract

OBJECTIVES:

Exposure to light can have acute alerting and circadian phase-shifting effects. This study investigated the effects of evening exposure to blue-enriched polychromatic white (BEL) vs. polychromatic white light (WL) on sleep inertia dissipation the following morning in older adults.

METHODS:

Ten healthy older adults (average age = 63.3 yrs; 6F) participated in a 13-day study comprising three baseline days, an initial circadian phase assessment, four days with 2-h evening light exposures, a post light exposure circadian phase assessment and three recovery days. Participants were randomized to either BEL or WL of the same irradiance for the four evening light exposures. On the next mornings at 2, 12, 22 and 32 min after each wake time, the participants completed a 90-s digit-symbol substitution test (DSST) to assess working memory, and objective alertness was assessed using a wake EEG recording. DSST and power density from the wake EEG recordings were compared between the two groups.

RESULTS:

DSST performance improved with time awake (p < 0.0001) and across study days in both light exposure groups (p < 0.0001). There was no main effect of group, although we observed a significant day x group interaction (p = 0.0004), whereby participants exposed to BEL performed significantly better on the first two mornings after light exposures than participants in WL (post-hoc, p < 0.05). On those days, the BEL group showed higher EEG activity in some of the frequency bins in the sigma and beta range (p < 0.05) on the wake EEG.

CONCLUSION:

Exposure to blue-enriched white light in the evening significantly improved DSST performance the following morning when compared to polychromatic white light. This was associated with a higher level of objective alertness on the wake EEG, but not with changes in sleep or circadian timing.

KEYWORDS:

Aging; Alertness; Circadian; Cognition; Light; Sleep

PMID:
29684473
PMCID:
PMC6124504
DOI:
10.1016/j.bbr.2018.04.021
[Indexed for MEDLINE]
Free PMC Article

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