title: Association of vitamin D status with socio-demographic factors in Calgary, Alberta: an ecological study using Census Canada data.
abstract: BACKGROUND
  Low 25-hydroxyvitamin D levels are a global health problem with northern countries such as Canada at particular risk. A number of sociodemographic factors have been reported to be associated with low vitamin D levels but prior studies have been limited by the ability of the researchers to gather this data directly from clinical trial participants. The purpose of this study was to use a novel methodology of inferring sociodemographic variables to evaluate the correlates of vitamin D levels in individuals dwelling in the City of Calgary, Alberta, Canada.
  
  
  METHODS
  We utilized data on vitamin D test results from Calgary Laboratory Services between January 1 2010 and August 31 2011. In addition to vitamin D level, we recorded age, sex, and vitamin D testing month as individual-level variables. We inferred sociodemographic variables by associating results with census dissemination areas and using Census Canada data to determine immigration status, education, median household income and first nations status as clustered variables. Associations between vitamin D status and the individual- and dissemination area-specific variables were examined using the population-averaged regression model by a generalized estimating equations approach to account for the clustering in the data.
  
  
  RESULTS
  158,327 individuals were included. Age, sex, month of vitamin D testing (at an individual level), and education, immigrant status, first nations status and income (at an aggregate level) were all statistically significant predictors of vitamin D status.
  
  
  CONCLUSIONS
  Vitamin D status was associated with a number of sociodemographic variables. Knowledge of these variables may improve targeted education and public health initiatives.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Calgary, Calgary, Alberta, Canada. Christopher.naugler@cls.ab.ca
authors.forename: Christopher
authors.initials: C
authors.lastname: Naugler
authors.forename: Jianguo
authors.initials: J
authors.lastname: Zhang
authors.forename: Dan
authors.initials: D
authors.lastname: Henne
authors.forename: Paul
authors.initials: P
authors.lastname: Woods
authors.forename: Brenda R
authors.initials: BR
authors.lastname: Hemmelgarn
mesh_terms: D000328:Adult; D017677:Age Distribution; D000368:Aged; D000416:Alberta / Q000453:epidemiology; D019352:Censuses; D004522:Educational Status; D054242:Emigrants and Immigrants / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007182:Income / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D017678:Sex Distribution; D013997:Time Factors; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000453:epidemiology*
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D