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Preventive effect of morning light exposure on relapse into depressive episode in bipolar disorder
Author(s) -
Esaki Yuichi,
Obayashi Kenji,
Saeki Keigo,
Fujita Kiyoshi,
Iwata Nakao,
Kitajima Tsuyoshi
Publication year - 2021
Publication title -
acta psychiatrica scandinavica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.849
H-Index - 146
eISSN - 1600-0447
pISSN - 0001-690X
DOI - 10.1111/acps.13287
Subject(s) - hazard ratio , bipolar disorder , morning , confidence interval , medicine , light therapy , confounding , mood , proportional hazards model , depression (economics) , psychiatry , psychology , economics , macroeconomics
Objective Light therapy has been suggested to have a curative effect on bipolar depression; however, preventive effects of light exposure on depressive episodes remain unclear. This study evaluated whether daytime light exposure in real‐life situations was associated with a preventive effect on relapse into depressive episodes in patients with bipolar disorder. Methods This prospective, naturalistic, observational study was conducted in Japan between August 2017 and June 2020. Outpatients with bipolar disorder were objectively evaluated for daytime light exposure over 7 consecutive days using an actigraph that could measure ambient light at baseline assessment and then assessed at 12‐month follow‐up for relapse into mood episodes. Results Of 202 participants, 198 (98%) completed follow‐up at 12 months and 78 (38%) experienced relapse into depressive episodes during follow‐up. In a Cox proportional hazards model adjusting for potential confounders, a longer time above 1000 lux at daytime was significantly associated with decrease in relapse into depressive episodes (per log min; hazard ratio, 0.66; 95% confidence interval, 0.50–0.91). In addition, a higher average illuminance and longer time above 1000 lux in the morning exhibited a significant decrease in relapse into depressive episodes (per log lux and per log min; hazard ratio, 0.65 and 0.61; 95% confidence interval, 0.49–0.86 and 0.47–0.78, respectively). The association between daytime light exposure and relapse into manic/hypomanic/mixed episodes was not significantly different. Conclusion A significant association was observed between increased daytime light exposure, mainly in the morning, and decreased relapse into depressive episodes.