Effects of Season and Daylight Saving Time Shifts on Sleep Symptoms: Canadian Longitudinal Study on Aging

Abstract

Background and Objectives: There has been conflicting evidence regarding the association between seasonal changes and daylight-savings time and sleep disorders. This topic is of current particular interest, as the United States and Canada are considering the elimination of seasonal clock changes. The aim of this study is to compare sleep symptoms among participants who were interviewed in different seasons, and before/after the transition into daylight saving time (DST) and standard time (ST). Methods: 30,097 people aged 45–85 years taking part in the Canadian Longitudinal Study on Aging (CLSA) were studied. Participants completed a questionnaire on sleep duration, satisfaction, sleep-onset insomnia, sleep-maintenance insomnia, and hypersomnolence symptoms. Sleep disorders were compared between participants who were interviewed during different seasons and at different times of the year (DST/ST). Data was analyzed using Chi Square, ANOVA, binary logistic, and linear regression tests. Results: Among participants interviewed in different seasons, we found no difference in dissatisfaction with sleep, sleep-onset, sleep-maintenance, and hypersomnolence. Those interviewed in summer had slightly shorter sleep duration compared to winter (6.76±1.2 vs. 6.84±1.3 hours). Participants interviewed one week before versus one week after DST transition showed no difference in sleep symptoms, except for a 9-minute decrease in sleep duration a week after transition. However, those who were interviewed a week after transition to ST compared to a week before reported more dissatisfaction with sleep (28% vs. 22.6%, adjusted odds ratio [95%CI]=1.34 [1.02,1.76]), higher sleep-onset insomnia (7.1% vs. 3.3%, AOR=2.26 [1.19,4.27]), higher sleep-maintenance insomnia (12.9% vs. 8.2%, AOR=1.64 [1.02,2.66]), and more hypersomnolence with adequate sleep (7.3% vs. 3.6%, AOR=2.08 [1.14,3.79]. Discussion: We found small seasonal variations in sleep duration but no difference in other sleep symptoms. The transition from DST to ST was associated with a transient increase in sleep disorders.