title: Short or long sleep duration is associated with memory impairment in older Chinese: the Guangzhou Biobank Cohort Study.
abstract: OBJECTIVE
  To examine the association between sleep-related factors and memory impairment.
  
  
  METHODS
  Cross-sectional study
  
  
  METHODS
  Community-based study in Guangzhou, China.
  
  
  METHODS
  28,670 older Chinese (20,776 women and 7,894 men) aged 50 to 85 years.
  
  
  RESULTS
  Demographic and socioeconomic data, sleep-related factors, and cognitive function were collected by face-to-face interview. Potential confounders, such as employment and occupational status, smoking, alcohol and tea use, physical activity, self-rated health, anthropometry, blood pressure, and fasting plasma glucose and lipids were measured. After adjusting for multiple potential confounders, an inverted U-shaped association between sleep duration and delayed word recall test (DWRT) score, a validated measure of memory impairment, was found, with 7 to 8 h of habitual sleep duration showing the highest score (P-values for trend from 3 to 7 h and from 7 to ≥ 10 h were all ≤ 0.001). Compared to sleep duration of 7 h, the adjusted odds ratio for memory impairment from the sleep duration of 3 to 4 or ≥ 10 h was 1.29 (95% confidence interval 1.07-1.56) and 1.52 (1.25-1.86), respectively. Subjects with daily napping, morning tiredness, or insomnia had significantly lower DWRT scores than those without (P ranged from < 0.001 to 0.01).
  
  
  CONCLUSIONS
  Short or long sleep duration was an important sleep-related factor independently associated with memory impairment and may be a useful marker for increased risk of cognitive impairment in older people.
authors.affiliation: Department of Community Medicine, School of Public Health, University of Hong Kong, Hong Kong.
authors.forename: Lin
authors.initials: L
authors.lastname: Xu
authors.forename: Chao Qiang
authors.initials: CQ
authors.lastname: Jiang
authors.forename: Tai Hing
authors.initials: TH
authors.lastname: Lam
authors.forename: Bin
authors.initials: B
authors.lastname: Liu
authors.forename: Ya Li
authors.initials: YL
authors.lastname: Jin
authors.forename: Tong
authors.initials: T
authors.lastname: Zhu
authors.forename: Wei Sen
authors.initials: WS
authors.lastname: Zhang
authors.forename: Kar Keung
authors.initials: KK
authors.lastname: Cheng
authors.forename: G Neil
authors.initials: GN
authors.lastname: Thomas
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D016009:Chi-Square Distribution; D002681:China; D016001:Confidence Intervals; D003430:Cross-Sectional Studies; D004522:Educational Status; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008569:Memory Disorders / Q000209:etiology* / Q000503:physiopathology; D008875:Middle Aged; D009483:Neuropsychological Tests; D016017:Odds Ratio; D012737:Sex Factors; D012890:Sleep / Q000502:physiology*; D013997:Time Factors