title: Seasonal variation in 25-hydroxyvitamin D concentrations in the cardiovascular health study.
abstract: Low circulating concentrations of 25-hydroxyvitamin D (25(OH)D) are associated with adverse health outcomes in diverse populations. However, 25(OH)D concentrations vary seasonally with varying exposure to sunlight, so single measurements may poorly reflect long-term 25(OH)D exposure. The authors investigated cyclical trends in average serum 25(OH)D concentrations among 2,298 individuals enrolled in the Cardiovascular Health Study of community-based older adults (1992-1993). A sinusoidal model closely approximated observed 25(OH)D concentrations and fit the data significantly better than did a mean model (P < 0.0001). The mean annual 25(OH)D concentration was 25.1 ng/mL (95% confidence interval: 24.7, 25.5), and the mean peak-trough difference was 9.6 ng/mL (95% confidence interval: 8.5, 10.7). Male sex, higher latitude of study site, and greater physical activity levels were associated with larger peak-trough difference in 25(OH)D concentration (each P < 0.05). Serum concentrations of intact parathyroid hormone and bone-specific alkaline phosphatase also varied in a sinusoidal fashion (P < 0.0001), inversely to 25(OH)D. In conclusion, serum 25(OH)D varies in a sinusoidal manner, with large seasonal differences relative to mean concentration and laboratory evidence of biologic sequelae. Single 25(OH)D measurements might not capture overall vitamin D status, and the extent of misclassification could vary by demographic and behavioral factors. Accounting for collection time may reduce bias in research studies and improve decision-making in clinical care.
authors: The Ohio State University, 1841 Neil Avenue, Columbus, OH 43210-1240, USA. ashoben@cph.osu.edu
authors: Abigail B
authors: AB
authors: Shoben
authors: Bryan
authors: B
authors: Kestenbaum
authors: Gregory
authors: G
authors: Levin
authors: Andrew N
authors: AN
authors: Hoofnagle
authors: Bruce M
authors: BM
authors: Psaty
authors: David S
authors: DS
authors: Siscovick
authors: Ian H
authors: IH
authors: de Boer
mesh_terms: D000368:Aged; D015415:Biomarkers; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D044469:Racial Groups; D012111:Residence Characteristics; D012621:Seasons; D012737:Sex Factors; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D015415:Biomarkers; D014807:Vitamin D; C104450:25-hydroxyvitamin D