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Author (up) Esaki, Y.; Kitajima, T.; Obayashi, K.; Saeki, K.; Fujita, K.; Iwata, N. url  doi
  Title Light exposure at night and sleep quality in bipolar disorder: the APPLE cohort study Type Journal Article
  Year 2019 Publication Journal of Affective Disorders Abbreviated Journal Journal of Affective Disorders  
  Volume 257 Issue Pages 314-320  
  Keywords Human Health; mood disorders; Bipolar Disorder; Sleep; sleep efficiency; sleep quality  
  Abstract Background

Sleep disturbance in bipolar disorder (BD) is common and is associated with a risk for mood episode recurrence. Thus, it is important to identify factors that are related to sleep disturbance in BD. This cross-sectional study investigated the association between exposure to light at night (LAN) and sleep parameters in patients with BD.


The sleep parameters of 175 outpatients with BD were recorded using actigraphy at their homes for seven consecutive nights and were evaluated using the Insomnia Severity Index (ISI). The average LAN intensity in the bedroom during bedtime and rising time was measured using a portable photometer, and the participants were divided into two groups: “Light” (≥5 lux) and “Dark” (<5 lux). The association between LAN and sleep parameters was tested with multivariable analysis by adjusting for potential confounder such as age, gender, current smoker, mood state, day length, daytime light exposure, and sedative medications.


After adjusting for potential confounder, the actigraphy sleep parameters showed significantly lower sleep efficiency (mean, 80.1% vs. 83.4%; p = 0.01), longer log-transformed sleep onset latency (2.9 vs. 2.6 min; p = 0.01), and greater wake after sleep onset (51.4 vs. 41.6 min; p = 0.02) in the Light group than in the Dark group. Whereas, there were no significant differences in the ISI scores between the groups.


This was a cross-sectional study; therefore, the results do not necessarily imply that LAN causes sleep disturbance.


Reducing LAN exposure may contribute to improved sleep quality in patients with BD.
  Address Department of Psychiatry, Okehazama Hospital, Aichi, Japan; esakiz(at)  
  Corporate Author Thesis  
  Publisher Elsevier Place of Publication Editor  
  Language English Summary Language English Original Title  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0165-0327 ISBN Medium  
  Area Expedition Conference  
  Notes Approved no  
  Call Number GFZ @ kyba @ Serial 2561  
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