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. 2011 Dec 15;174(12):1363-72.
doi: 10.1093/aje/kwr258. Epub 2011 Nov 23.

Seasonal variation in 25-hydroxyvitamin D concentrations in the cardiovascular health study

Abigail B Shoben  1 , Bryan Kestenbaum, Gregory Levin, Andrew N Hoofnagle, Bruce M Psaty, David S Siscovick, Ian H de Boer
Affiliations

Seasonal variation in 25-hydroxyvitamin D concentrations in the cardiovascular health study

Abigail B Shoben et al. Am J Epidemiol. .

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.

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Figures

Figure 1.
Figure 1.
Fitted sinusoidal model for observed serum 25-hydroxyvitamin D (25(OH)D) concentration superimposed on plot of observed monthly mean (standard deviation) values for 25-hydroxyvitamin D concentration among 2,298 participants in the Cardiovascular Health Study, 1992–1993. Bars, 1 standard deviation.
Figure 2.
Figure 2.
Modeled mean serum concentrations of 25-hydroxyvitamin D (25(OH)D) over the course of the calendar year by sex and race, adjusted for the main effects of age and clinical site, Cardiovascular Health Study, 1992–1993. A) Compared with women, men had higher mean 25(OH)D concentrations throughout the year and greater seasonal variation. B) Compared with black participants, white participants had higher mean 25(OH)D concentrations throughout the year but no difference in seasonal variation.
Figure 3.
Figure 3.
Fitted sinusoidal model for observed serum concentrations of parathyroid hormone (PTH), bone-specific alkaline phosphatase (BAP), calcium, and phosphate, each superimposed on plot of observed monthly mean (standard deviation) values, Cardiovascular Health Study, 1992–1993. PTH and BAP are presented on the geometric mean (log) scale. Bars, 1 standard deviation.
See this image and copyright information in PMC

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