Vitamin D status and parathyroid hormone levels in relation to blood pressure: a population-based study in older men and women

Background. Evidence is accumulating that the vitamin D endocrine system has physiological functions beyond bone health including a role in the regulation of blood pressure. Effects of poor vitamin D status on blood pressure may be mediated by elevated parathyroid hormone (PTH) levels. Aim. To evaluate whether serum 25-hydroxyvitamin D [25(OH)D] and PTH levels are independently associated with blood pressure in a population-based study of older men and women. Methods. Subjects were participants of the Longitudinal Aging Study Amsterdam, aged 65 years and older. In 1205 participants, serum 25(OH)D and PTH levels were determined and diastolic and systolic blood pressure were measured. Linear and logistic regression analyses were performed with adjustments for age, sex, region, season, lifestyle factors (physical activity, smoking, alcohol intake), and waist circumference. Results. Serum 25(OH)D was not significantly associated with diastolic (beta 0.00, P = 0.98) or systolic (beta 0.06, P = 0.11) blood pressure. In contrast, higher ln-PTH levels were significantly associated with higher diastolic (beta 1.93, P = 0.03) and systolic (beta 4.67, P = 0.01) blood pressure. Higher PTH levels were associated with a substantially higher prevalence of hypertension (OR 2.00, 95% CI 1.31-3.06 for the highest versus the lowest quartile), whereas 25(OH)D showed no significant association (OR 0.89, 95% CI 0.47-1.69 for the lowest versus the highest 25(OH)D category). Conclusion. These results indicate that PTH is a potentially modifiable determinant of blood pressure in the general elderly population. Serum 25(OH)D, however, was not associated with blood pressure, possibly due to the relatively high levels in our population.