title: Vitamin D Status and Rates of Cognitive Decline in a Multiethnic Cohort of Older Adults.
abstract: OBJECTIVE
  Vitamin D (VitD) deficiency is associated with brain structural abnormalities, cognitive decline, and incident dementia.
  
  
  OBJECTIVE
  To assess associations between VitD status and trajectories of change in subdomains of cognitive function in a cohort of ethnically diverse older adults.
  
  
  METHODS
  Longitudinal multiethnic cohort study of 382 participants in an outpatient clinic enrolled between February 2002 and August 2010 with baseline assessment and yearly follow-up visits. Serum 25-hydroxyvitamin D (25-OHD) was measured, with VitD status defined as the following: deficient, less than 12 ng/mL (to convert to nanomoles per liter, multiply by 2.496); insufficient, 12 to less than 20 ng/mL; adequate, 20 to less than 50 ng/mL; or high, 50 ng/mL or higher. Subdomains of cognitive function were assessed using the Spanish and English Neuropsychological Assessment Scales. Associations were evaluated between 25-OHD levels (as continuous and categorical [deficient, insufficient, or adequate]) and trajectories of cognitive decline.
  
  
  METHODS
  Serum 25-OHD levels, cognitive function, and associations between 25-OHD levels and trajectories of cognitive decline.
  
  
  RESULTS
  Participants (N = 382 at baseline) had a mean (SD) age of 75.5 (7.0) years; 61.8% were women; and 41.4% were white, 29.6% African American, 25.1% Hispanic, and 3.9% other race/ethnicity. Diagnosis at enrollment included 17.5% with dementia, 32.7% with mild cognitive impairment, and 49.5% cognitively normal. The mean (SD) 25-OHD level was 19.2 (11.7) ng/mL, with 26.2% of participants being VitD deficient and 35.1% insufficient. The mean (SD) 25-OHD levels were significantly lower for African American and Hispanic participants compared with white participants (17.9 [15.8] and 17.2 [8.4] vs 21.7 [10.0] ng/mL, respectively; P < .001 for both). The mean (SD) 25-OHD levels were similarly lower in the dementia group compared with the mild cognitive impairment and cognitively normal groups (16.2 [9.4] vs 20.0 [10.3] and 19.7 [13.1] ng/mL, respectively; P = .006). The mean (SD) follow-up was 4.8 (2.5) years. Rates of decline in episodic memory and executive function among VitD-deficient (episodic memory: β = -0.04 [SE = 0.02], P = .049; executive function: β = -0.05 [SE = 0.02], P = .01) and VitD-insufficient (episodic memory: β = -0.06 [SE = 0.02], P < .001; executive function: β = -0.04 [SE = 0.02], P = .008) participants were greater than those with adequate status after controlling for age, sex, education, ethnicity, body mass index, season of blood draw, vascular risk, and apolipoprotein E4 genotype. Vitamin D status was not significantly associated with decline in semantic memory or visuospatial ability. Exclusion of participants with dementia did not substantially affect the associations between VitD status and rates of cognitive decline.
  
  
  CONCLUSIONS
  Low VitD status was associated with accelerated decline in cognitive function domains in ethnically diverse older adults, including African American and Hispanic individuals who exhibited a high prevalence of VitD insufficiency or deficiency. It remains to be determined whether VitD supplementation slows cognitive decline.
authors.affiliation: Department of Nutritional Sciences, Rutgers University, New Brunswick, New Jersey2Department of Medical Pathology and Laboratory Medicine, University of California, Davis.
authors.forename: Joshua W
authors.initials: JW
authors.lastname: Miller
authors.affiliation: Division of Biostatistics, Department of Public Health Sciences, University of California, Davis.
authors.forename: Danielle J
authors.initials: DJ
authors.lastname: Harvey
authors.affiliation: Division of Biostatistics, Department of Public Health Sciences, University of California, Davis.
authors.forename: Laurel A
authors.initials: LA
authors.lastname: Beckett
authors.affiliation: Department of Medical Pathology and Laboratory Medicine, University of California, Davis.
authors.forename: Ralph
authors.initials: R
authors.lastname: Green
authors.affiliation: Department of Neurology, University of California, Davis.
authors.forename: Sarah Tomaszewski
authors.initials: ST
authors.lastname: Farias
authors.affiliation: Department of Neurology, University of California, Davis.
authors.forename: Bruce R
authors.initials: BR
authors.lastname: Reed
authors.affiliation: Department of Neurology, University of California, Davis.
authors.forename: John M
authors.initials: JM
authors.lastname: Olichney
authors.affiliation: Department of Neurology, University of California, Davis.
authors.forename: Dan M
authors.initials: DM
authors.lastname: Mungas
authors.affiliation: Department of Neurology, University of California, Davis.
authors.forename: Charles
authors.initials: C
authors.lastname: DeCarli
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood; D044383:Black People / Q000208:ethnology*; D002140:California / Q000208:ethnology; D003072:Cognition Disorders / Q000097:blood* / Q000208:ethnology; D060825:Cognitive Dysfunction / Q000097:blood / Q000208:ethnology; D003704:Dementia / Q000097:blood* / Q000208:ethnology; D005260:Female; D006630:Hispanic or Latino / Q000208:ethnology*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood* / Q000208:ethnology; D044465:White People / Q000208:ethnology*; D001741:Black or African American
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D