title: Vitamin D insufficiency and cognitive impairment in Asians: a multi-ethnic population-based study and meta-analysis.
abstract: BACKGROUND
  The relationship between vitamin D insufficiency and cognitive impairment remains equivocal in Asians. We examined the association between circulating 25-hydroxyvitamin D (25OHD) concentration and cognitive performance in a large multi-ethnic Singaporean population-based study. We also conducted a meta-analysis of 25OHD concentrations amongst cognitively impaired older adults in Asia.
  
  
  METHODS
  Our population-based cross-sectional study included 2273 persons ≥60 years of age from the Singapore Epidemiology of Eye Diseases (SEED) study (mean ± SD age 70.4 ± 6.2 years; 44.7% female), who were categorized according to 25OHD concentration (i.e. ≤10, 10.1-20 and >20 ng mL(-1) ). The 25OHD concentration was measured and adjusted to reflect a deseasonalized value. Cognition was assessed using the total and domain scores of the Abbreviated Mental Test (AMT). Global cognitive impairment was defined as AMT score of ≤6 if 0-6 years of education and AMT score of ≤8 if >7 years of education. Fully adjusted multivariate models were used. We included seven studies in a meta-analysis of 25OHD and cognition in Asia (6068 participants; 1179 cognitively impaired cases).
  
  
  RESULTS
  Participants with 25OHD levels >20 ng mL(-1) (n = 1302) had higher AMT total scores (mean ± SD 8.5 ± 1.9) and were less likely to have cognitive impairment (14.1%) than participants with lower 25OHD levels (overall P < 0.001, P-trend < 0.001). Deseasonalized 25OHD concentration was associated with AMT score (β = 0.10 per 10 ng mL(-1) , P = 0.035). Vitamin D insufficiency (25OHD ≤20 ng mL(-1) ) was associated with global cognitive impairment (OR 1.56, P = 0.028). Specifically, 25OHD concentration correlated with semantic memory (r = 0.08, P = 0.009) and orientation in time (r = 0.09, P = 0.003). In the meta-analysis, the pooled mean 25OHD difference was -6.83 ng mL(-1) (95% confidence interval -11.36; -2.30), indicating lower 25OHD concentrations amongst cognitively impaired compared to cognitively healthy participants in Asia.
  
  
  CONCLUSIONS
  Vitamin D insufficiency is associated with a greater likelihood of and more severe cognitive impairment in Asian populations.
authors.affiliation: Division of Geriatric Medicine, Department of Neuroscience, Angers University Hospital, University Memory Clinic of Angers, UNAM, University of Angers, Angers, France.|Department of Medical Biophysics, Schulich School of Medicine and Dentistry, Robarts Research Institute, The University of Western Ontario, London, ON, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Annweiler
authors.affiliation: Singapore Eye Research Institute, Singapore.|Singapore National Eye Centre, Singapore.|Neuroscience and Behavioural Disorders, Duke-NUS, Singapore.|Division of Ophthalmology, Department of Neuroscience, Angers University Hospital, Angers, France.
authors.forename: D
authors.initials: D
authors.lastname: Milea
authors.affiliation: Departments of Medicine and Ophthalmology, Duke University Medical School, Durham, NC, USA.|Duke Aging Center, Duke University, Durham, NC, USA.|Durham VA Medical Center, Geriatrics Research Education and Clinical Center, Durham, NC, USA.
authors.forename: H E
authors.initials: HE
authors.lastname: Whitson
authors.affiliation: Singapore Eye Research Institute, Singapore.|Singapore National Eye Centre, Singapore.|Ophthalmology and Visual Sciences Academic Clinical Program, Medical School, Duke-NUS, Singapore.|Department of Ophthalmology, National University of Singapore, Singapore.
authors.forename: C-Y
authors.initials: CY
authors.lastname: Cheng
authors.affiliation: Singapore Eye Research Institute, Singapore.|Singapore National Eye Centre, Singapore.|Ophthalmology and Visual Sciences Academic Clinical Program, Medical School, Duke-NUS, Singapore.|Department of Ophthalmology, National University of Singapore, Singapore.
authors.forename: T-Y
authors.initials: TY
authors.lastname: Wong
authors.affiliation: Singapore Eye Research Institute, Singapore.|Memory Aging & Cognition Centre, National University Health System, Singapore.
authors.forename: M K
authors.initials: MK
authors.lastname: Ikram
authors.affiliation: Singapore Eye Research Institute, Singapore.|Singapore National Eye Centre, Singapore.|Ophthalmology and Visual Sciences Academic Clinical Program, Medical School, Duke-NUS, Singapore.|Department of Ophthalmology, National University of Singapore, Singapore.
authors.forename: E L
authors.initials: EL
authors.lastname: Lamoureux
authors.affiliation: Singapore Eye Research Institute, Singapore.|Ophthalmology and Visual Sciences Academic Clinical Program, Medical School, Duke-NUS, Singapore.|Department of Ophthalmology, National University of Singapore, Singapore.
authors.forename: C
authors.initials: C
authors.lastname: Sabanayagam
mesh_terms: D000368:Aged; D044466:Asian People / Q000523:psychology*; D003072:Cognition Disorders / Q000097:blood / Q000150:complications* / Q000208:ethnology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D012846:Singapore; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood; D014808:Vitamin D Deficiency / Q000150:complications* / Q000208:ethnology*
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D
keywords: Asia; cognition; older adults; vitamin D