Abstract P424: Prospective Associations of Serum 25-hydroxyvitamin D and Parathyroid Hormone with Arterial Function among Older Adults

Introduction: Low vitamin D and high parathyroid hormone (PTH) concentrations have been associated with higher risk of cardiovascular disease in the general population. The mechanisms by which lower 25-hydroxyvitamin D (25OHD) -an established marker of vitamin D status- and PTH excess may confer vascular risk remain largely unknown. Hypothesis: We tested the hypothesis whether lower 25-hydroxyvitamin D (25OHD) and higher parathyroid hormone (PTH) concentrations are individually, and in combination, associated with arterial function measures, both cross-sectionally and after 8 years of follow-up in older adults. Methods: We used data from the Hoorn Study a prospective population-based cohort in the Netherlands. We included 535 participants for cross-sectional analyses with baseline measurements obtained between 2000- 2001, and 291 participants for longitudinal analyses with follow-up measurements obtained between 2007-2009. Serum 25OHD and intact PTH concentrations were measured using immunoassays. Outcomes were carotid-femoral pulse wave velocity and augmentation index. We used multivariate linear regression analyses for season-and-sex specific 25OHD and PTH quartiles to calculate regression coefficients. Results: Mean age at baseline was 70±6.3 years, and 50% were female. Median 25OHD was 54.2 nmol/L (interquartile range: 26.2-82.2) and median PTH 6.1 pmol/L (3.8-8.4). Mean pulse wave velocity and augmentation index were 10.0±3.0 (m/s) and 20.7±8.2 (%), respectively. In cross-sectional analyses, the lowest 25OHD quartile compared with the highest was associated with greater pulse wave velocity; however, the associations attenuated after adjustments 0.6 (95% CI -0.1, 1.3). In longitudinal analyses, neither 25OHD nor PTH was associated with greater pulse wave velocity and augmentation index. The results of the combination of low 25OHD and high PTH revealed no significant associations with arterial function measures. Conclusions: Among older adults, serum 25OHD and PTH concentrations were not associated with arterial function measures. Cardiovascular risk associated with low 25OHD and high PTH may not be explained by arterial stiffening or wave reflections.