title: Sleep duration and its correlates in middle-aged and elderly Chinese women: the Shanghai Women's Health Study.
abstract: BACKGROUND
  Abnormal sleep duration, either long or short, is associated with disease risk and mortality. Little information is available on sleep duration and its correlates among Chinese women.
  
  
  METHODS
  Using information collected from 68,832 women who participated in the Shanghai Women's Health Study (SWHS), we evaluated sleep duration and its correlations with sociodemographic and lifestyle factors, health status, and anthropometric measurements and their indexes using polynomial logistic regression.
  
  
  RESULTS
  The mean age of the study population was 59.6 years (SD=9.0; range: 44.6-79.9 years) at time of sleep duration assessment. Approximately 80% of women reported sleeping 6-8 h/day, 11.5% slept 5h or less, and 8.7% slept 9h or more. As expected, age was the strongest predictor for sleep duration and was negatively correlated with sleep duration. In general, sleep duration was positively associated with energy intake, intakes of total meat and fruits, body mass index (BMI), waist-hip ratio (WHR), and waist circumference (WC) after adjustment for age and other factors. Both short and long sleep duration were negatively associated with education level, family income, and leisure-time physical activity and positively associated with number of live births, history of night shift work, and certain chronic diseases, compared to sleep duration around 7 h/day (6.5-7.4h/day). Short sleep duration was related to tea consumption and passive smoking. Long sleep duration was related to menopausal status and marital status.
  
  
  CONCLUSIONS
  In this large, population-based study, we found that sleep duration among middle-aged and elderly Chinese women was associated with several sociodemographic and lifestyle factors and with disease status. The main limitation of the study is the cross-sectional design that does not allow us to draw any causal inference. However, this study provides information for future investigation into the nature of these associations so that recommendations can be developed to reduce sleep problems in middle-aged and elderly Chinese women. It also provides important information on potential confounders for investigation of sleep duration on health outcomes in this population.
authors.affiliation: Vanderbilt Epidemiology Center, Department of Medicine and Vanderbilt-Ingram Cancer Center, Nashville, TN 37203-1738, USA.
authors.forename: Xiangdong
authors.initials: X
authors.lastname: Tu
authors.forename: Hui
authors.initials: H
authors.lastname: Cai
authors.forename: Yu-Tang
authors.initials: YT
authors.lastname: Gao
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Wu
authors.forename: Bu-Tian
authors.initials: BT
authors.lastname: Ji
authors.forename: Gong
authors.initials: G
authors.lastname: Yang
authors.forename: Honglan
authors.initials: H
authors.lastname: Li
authors.forename: Wei
authors.initials: W
authors.lastname: Zheng
authors.forename: Xiao Ou
authors.initials: XO
authors.lastname: Shu
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D015992:Body Mass Index; D002681:China / Q000453:epidemiology; D004032:Diet / Q000706:statistics & numerical data; D002149:Energy Intake; D005260:Female; D006304:Health Status; D006801:Humans; D016015:Logistic Models; D017533:Marital Status; D008593:Menopause; D008875:Middle Aged; D012890:Sleep; D012893:Sleep Wake Disorders / Q000150:complications* / Q000453:epidemiology; D013997:Time Factors; D055105:Waist Circumference; D049629:Waist-Hip Ratio