Factors Associated With Change in 25-Hydroxyvitamin D Levels Over Longitudinal Follow-Up in the ARIC Study.

CONTEXT

A single measurement of 25-hydroxyvitamin D (25 [OH] D) may not accurately reflect long-term vitamin D status. Little is known about change in 25(OH)D levels over time, particularly among blacks.

OBJECTIVE

The objective of the study was to determine the longitudinal changes in 25(OH)D levels among Atherosclerosis Risk in Communities (ARIC) study participants.

DESIGN

This was a longitudinal study.

SETTING

The study was conducted in the general community.

PARTICIPANTS

A total of 9890 white and 3222 black participants at visit 2 (1990-1992), 888 whites and 876 blacks at visit 3 (1993-1994), and 472 blacks at the brain visit (2004-2006) participated in the study.

MAIN OUTCOME MEASURE

The 25(OH)D levels were measured, and regression models were used to assess the associations between clinical factors and longitudinal changes in 25(OH)D.

RESULTS

Vitamin D deficiency (50 nmol/L [20 ng/mL]) was seen in 23% and 25% of whites at visits 2 and 3, and in 61%, 70%, and 47% of blacks at visits 2, 3, and the brain visit, respectively. The 25(OH)D levels were correlated between visits 2 and 3 (3 y interval) among whites (r = 0.73) and blacks (r = 0.66). Among blacks, the correlation between visit 2 and the brain visit (14 y interval) was 0.33. Overall, increases in 25(OH)D levels over time was associated with male gender, use of vitamin D supplements, greater physical activity, and higher high-density lipoprotein-cholesterol (P .001). Decreases in 25(OH)D levels over time were associated with current smoking, higher body mass index, higher education, diabetes, and hypertension (all P .05).

CONCLUSIONS

Among US blacks and whites, 25(OH)D levels remained relatively stable over time. Certain modifiable lifestyle factors were associated with change in 25(OH)D levels over time.