title: Vitamin D levels and cognition in elderly adults in China.
abstract: OBJECTIVE
  To evaluate the association between vitamin D level and cognitive impairment in individuals aged 60 and older.
  
  
  METHODS
  Cross-sectional cohort study.
  
  
  METHODS
  Chinese Longitudinal Healthy Longevity Survey, a community-based cohort study in areas in China where the density of centenarians is exceptionally high.
  
  
  METHODS
  Individuals with mean age of 84.9 ± 12.7 (N = 2,004).
  
  
  METHODS
  Participants' cognitive state was evaluated using the Mini-Mental State Examination (MMSE). Vitamin D was measured in plasma using an enzyme-linked immunoassay.
  
  
  RESULTS
  The cross-sectional association between quartiles of plasma vitamin D level and cognitive impairment (MMSE score <18) was modeled using logistic regressions. Plasma vitamin D levels were lower in individuals with cognitive impairment (31.9 ± 15.3 nmol/L) than in those without (45.6 ± 19.6 nmol/L). There was a reverse association between plasma vitamin D and cognitive impairment. After adjusting for age, sex, chronic conditions, smoking and drinking habits, outdoor activities, depression, and activity of daily living limitations, the association remained significant. The multivariable-adjusted odds ratio for lowest versus highest vitamin D levels was 2.15 (95% confidence interval (CI) = 1.05-4.41) for cognitive impairment, and the multivariable odds ratio associated with a 1-standard deviation decrement in plasma vitamin D was 1.32 (95% CI = 1.00-1.74) for cognitive impairment.
  
  
  CONCLUSIONS
  Low plasma vitamin D levels were associated with greater odds of cognitive impairment. Further prospective studies in Asian populations are needed to examine the causal direction of this association.
authors.affiliation: Health Services and Systems Research, Duke-NUS Graduate Medical School Singapore, Singapore; Department of Public Health Medicines, Faculty of Medicine, University of Tsukuba, Tsukuba, Japan.
authors.forename: Choy-Lye
authors.initials: CL
authors.lastname: Chei
authors.forename: Prassanna
authors.initials: P
authors.lastname: Raman
authors.forename: Zhao-Xue
authors.initials: ZX
authors.lastname: Yin
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Shi
authors.forename: Yi
authors.initials: Y
authors.lastname: Zeng
authors.forename: David B
authors.initials: DB
authors.lastname: Matchar
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000097:blood* / Q000208:ethnology; D002112:Calcifediol / Q000097:blood*; D002681:China; D003431:Cross-Cultural Comparison; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008136:Longevity; D008297:Male; D008609:Mental Status Schedule; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D013223:Statistics as Topic; D014808:Vitamin D Deficiency / Q000097:blood* / Q000208:ethnology
chemical_list: D002112:Calcifediol
keywords: China; cognition; elderly; oldest old; vitamin D