02559nas a2200349 4500008004100000022001400041245009700055210006900152260001600221300001200237490000800249520158900257653000901846653001501855653003401870653001301904653001101917653001101928653000901939653003001948653001201978653001601990653001402006100002302020700002202043700001902065700002502084700002002109700002402129700002002153856003602173 2011 eng d a1476-625600aSeasonal variation in 25-hydroxyvitamin D concentrations in the cardiovascular health study.0 aSeasonal variation in 25hydroxyvitamin D concentrations in the c c2011 Dec 15 a1363-720 v1743 a

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.

10aAged10aBiomarkers10aContinental Population Groups10aExercise10aFemale10aHumans10aMale10aResidence Characteristics10aSeasons10aSex Factors10aVitamin D1 aShoben, Abigail, B1 aKestenbaum, Bryan1 aLevin, Gregory1 aHoofnagle, Andrew, N1 aPsaty, Bruce, M1 aSiscovick, David, S1 ade Boer, Ian, H uhttps://chs-nhlbi.org/node/135303451nas a2200409 4500008004100000022001400041245015200055210006900207260001600276300001100292490000800303520226000311653000902571653001902580653001102599653002202610653001802632653001102650653000902661653002602670653001402696653003202710653002002742653001702762653001202779653001802791653001402809653002502823100002002848700001902868700003002887700001902917700002302936700002402959700002202983856003603005 2012 eng d a1539-370400aSerum 25-hydroxyvitamin D concentration and risk for major clinical disease events in a community-based population of older adults: a cohort study.0 aSerum 25hydroxyvitamin D concentration and risk for major clinic c2012 May 01 a627-340 v1563 a

BACKGROUND: Circulating concentrations of 25-hydroxyvitamin D [25-(OH)D] are used to define vitamin D deficiency. Current clinical 25-(OH)D targets based on associations with intermediate markers of bone metabolism may not reflect optimal levels for other chronic diseases and do not account for known seasonal variation in 25-(OH)D concentration.

OBJECTIVE: To evaluate the relationship of 25-(OH)D concentration with the incidence of major clinical disease events that are pathophysiologically relevant to vitamin D.

DESIGN: Cohort study.

SETTING: The Cardiovascular Health Study conducted in 4 U.S. communities. Data from 1992 to 2006 were included in this analysis.

PARTICIPANTS: 1621 white older adults.

MEASUREMENTS: Serum 25-(OH)D concentration (using a high-performance liquid chromatography-tandem mass spectrometry assay that conforms to National Institute of Standards and Technology reference standards) and associations with time to a composite outcome of incident hip fracture, myocardial infarction, cancer, or death.

RESULTS: Over a median 11-year follow-up, the composite outcome occurred in 1018 participants (63%). Defining events included 137 hip fractures, 186 myocardial infarctions, 335 incidences of cancer, and 360 deaths. The association of low 25-(OH)D concentration with risk for the composite outcome varied by season (P = 0.057). A concentration lower than a season-specific Z score of -0.54 best discriminated risk for the composite outcome and was associated with a 24% higher risk in adjusted analyses (95% CI, 9% to 42%). Corresponding season-specific 25-(OH)D concentrations were 43, 50, 61, and 55 nmol/L (17, 20, 24, and 22 ng/mL) in winter, spring, summer, and autumn, respectively.

LIMITATION: The observational study was restricted to white participants.

CONCLUSION: Threshold concentrations of 25-(OH)D associated with increased risk for relevant clinical disease events center near 50 nmol/L (20 ng/mL). Season-specific targets for 25-(OH)D concentration may be more appropriate than static targets when evaluating health risk.

PRIMARY FUNDING SOURCE: National Institutes of Health.

10aAged10aCause of Death10aFemale10aFollow-Up Studies10aHip Fractures10aHumans10aMale10aMyocardial Infarction10aNeoplasms10aProportional Hazards Models10aRisk Assessment10aRisk Factors10aSeasons10aUnited States10aVitamin D10aVitamin D Deficiency1 ade Boer, Ian, H1 aLevin, Gregory1 aRobinson-Cohen, Cassianne1 aBiggs, Mary, L1 aHoofnagle, Andy, N1 aSiscovick, David, S1 aKestenbaum, Bryan uhttps://chs-nhlbi.org/node/1384