title: High sleep duration variability is an independent risk factor for weight gain.
abstract: OBJECTIVE
  This study was conducted to evaluate the association between weight gain and variability of sleep duration.
  
  
  METHODS
  A retrospective cohort study was conducted involving apparently healthy individuals aged 20 years or older who underwent annual health checkup at the Center for Preventive Medicine, St. Luke's International Hospital, between 2007 and 2010. The body mass index (BMI) of each participant was measured, and the change in BMI during the study period was calculated. The sleep duration was obtained using a questionnaire that was filled out by participants each year, and the variability in the sleep duration was calculated by dividing the standard deviation (SD) of the sleep duration for 3 years by the square root of the number of data points. Multivariate linear regression analysis was used to explore the association between the change in BMI and the variability of the sleep duration, adjusting for age, sex, alcohol consumption, current smoking, baseline sleep duration, past medical history, and level of physical activity.
  
  
  RESULTS
  A total of 21,148 participants were included in this study. The mean age (SD) was 51 (12) years, and 10,993 (49.6%) participants were male. The mean baseline BMI was 22.4 (SD 3.2). According to the self-reported data, the mean sleep duration (SD) was 6.2 (1.0) h, and the mean of the SD of sleep duration for each participant was 0.32 (min-max, 0-7). The result of the linear regression analysis showed that greater variability in the sleep duration was independently related to an increase in BMI (β coefficient = 0.31; 95% CI = 0.01-0.61).
  
  
  CONCLUSIONS
  The variability of sleep duration is related to body weight gain. Maintaining a constant sleep duration may be recommended for controlling body weight.
authors.affiliation: Department of Medicine, St. Luke's International Hospital, Tokyo, Japan. daikoba@luke.or.jp
authors.forename: Daiki
authors.initials: D
authors.lastname: Kobayashi
authors.forename: Osamu
authors.initials: O
authors.lastname: Takahashi
authors.forename: Takuro
authors.initials: T
authors.lastname: Shimbo
authors.forename: Tomoya
authors.initials: T
authors.lastname: Okubo
authors.forename: Hiroko
authors.initials: H
authors.lastname: Arioka
authors.forename: Tsuguya
authors.initials: T
authors.lastname: Fukui
mesh_terms: D000328:Adult; D015992:Body Mass Index; D015331:Cohort Studies; D004734:Energy Metabolism / Q000502:physiology; D005260:Female; D005500:Follow-Up Studies; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007564:Japan; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology; D012189:Retrospective Studies; D012892:Sleep Deprivation / Q000503:physiopathology*; D015430:Weight Gain / Q000502:physiology*