title: A Population-Based Model to Consider the Effect of Seasonal Variation on Serum 25(OH)D and Vitamin D Status.
abstract: BACKGROUND
  We elaborated a model that predicts the centiles of the 25(OH)D distribution taking into account seasonal variation.
  
  
  METHODS
  Data from two Swiss population-based studies were used to generate (CoLaus) and validate (Bus Santé) the model. Serum 25(OH)D was measured by ultra high pressure LC-MS/MS and immunoassay. Linear regression models on square-root transformed 25(OH)D values were used to predict centiles of the 25(OH)D distribution. Distribution functions of the observations from the replication set predicted with the model were inspected to assess replication.
  
  
  RESULTS
  Overall, 4,912 and 2,537 Caucasians were included in original and replication sets, respectively. Mean (SD) 25(OH)D, age, BMI, and % of men were 47.5 (22.1) nmol/L, 49.8 (8.5) years, 25.6 (4.1) kg/m(2), and 49.3% in the original study. The best model included gender, BMI, and sin-cos functions of measurement day. Sex- and BMI-specific 25(OH)D centile curves as a function of measurement date were generated. The model estimates any centile of the 25(OH)D distribution for given values of sex, BMI, and date and the quantile corresponding to a 25(OH)D measurement.
  
  
  CONCLUSIONS
  We generated and validated centile curves of 25(OH)D in the general adult Caucasian population. These curves can help rank vitamin D centile independently of when 25(OH)D is measured.
authors.affiliation: Institute of Social and Preventive Medicine (IUMSP), University Hospital of Lausanne (CHUV), 1010 Lausanne, Switzerland.
authors.forename: Philippe
authors.initials: P
authors.lastname: Vuistiner
authors.affiliation: Institute of Social and Preventive Medicine (IUMSP), University Hospital of Lausanne (CHUV), 1010 Lausanne, Switzerland.
authors.forename: Valentin
authors.initials: V
authors.lastname: Rousson
authors.affiliation: Biomedicine, University Hospital of Lausanne, 1011 Lausanne, Switzerland.
authors.forename: Hugues
authors.initials: H
authors.lastname: Henry
authors.affiliation: Department of Genetic and Laboratory Medicine, Geneva University Hospitals, 1205 Geneva, Switzerland.
authors.forename: Pierre
authors.initials: P
authors.lastname: Lescuyer
authors.affiliation: Biomedicine, University Hospital of Lausanne, 1011 Lausanne, Switzerland.
authors.forename: Olivier
authors.initials: O
authors.lastname: Boulat
authors.affiliation: Unit of Population Epidemiology, Division of Primary Care Medicine, Department of Community Medicine, Primary Care and Emergency Medicine, Geneva University Hospitals, 1205 Geneva, Switzerland.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Gaspoz
authors.affiliation: Biomedicine, University Hospital of Lausanne, 1011 Lausanne, Switzerland.
authors.forename: Vincent
authors.initials: V
authors.lastname: Mooser
authors.affiliation: Department of Internal Medicine, Internal Medicine, University Hospital of Lausanne (CHUV), 1011 Lausanne, Switzerland.
authors.forename: Peter
authors.initials: P
authors.lastname: Vollenweider
authors.affiliation: Department of Internal Medicine, Internal Medicine, University Hospital of Lausanne (CHUV), 1011 Lausanne, Switzerland.
authors.forename: Gerard
authors.initials: G
authors.lastname: Waeber
authors.affiliation: Department for Ambulatory Care and Community Medicine, University of Lausanne, 1011 Lausanne, Switzerland.
authors.forename: Jacques
authors.initials: J
authors.lastname: Cornuz
authors.affiliation: Institute of Social and Preventive Medicine (IUMSP), University Hospital of Lausanne (CHUV), 1010 Lausanne, Switzerland.
authors.forename: Fred
authors.initials: F
authors.lastname: Paccaud
authors.affiliation: Institute of Social and Preventive Medicine (IUMSP), University Hospital of Lausanne (CHUV), 1010 Lausanne, Switzerland.
authors.forename: Murielle
authors.initials: M
authors.lastname: Bochud
authors.affiliation: Institute of Social and Preventive Medicine (IUMSP), University Hospital of Lausanne (CHUV), 1010 Lausanne, Switzerland ; Unit of Population Epidemiology, Division of Primary Care Medicine, Department of Community Medicine, Primary Care and Emergency Medicine, Geneva University Hospitals, 1205 Geneva, Switzerland ; Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA 30322, USA.
authors.forename: Idris
authors.initials: I
authors.lastname: Guessous
mesh_terms: D000328:Adult; D000368:Aged; D015992:Body Mass Index; D006801:Humans; D008875:Middle Aged; D008954:Models, Biological; D015203:Reproducibility of Results; D012621:Seasons; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood*
chemical_list: D014807:Vitamin D; C104450:25-hydroxyvitamin D