Vitamin D, parathyroid hormone, and blood pressure in the national health and nutrition examination surveys

Abstract

BackgroundPrevious research shows serum 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone (PTH) are each associated with blood pressure (BP), but it is unclear whether these associations are independent.MethodsCross-sectional data from the US National Health and Nutrition Examination Surveys (NHANES) during 2003-2006. Analyses were restricted to 7,561 participants aged 20 years with measurements of 25(OH)D, PTH, BP, BP treatment, smoking, physical activity, serum calcium, and creatinine. Results were adjusted for these plus demographic variables.ResultsSerum 25(OH)D was more strongly associated (inversely) with systolic than diastolic BP. Adjusted mean (standard error) difference in BP for the lowest 25(OH)D quintile (13ng/ml) was 3.5 (0.7) mm Hg for systolic BP and 1.8 (0.6) mm Hg for diastolic BP, compared with the highest quintile (30ng/ml). In contrast, PTH was positively associated with both systolic and diastolic BP (P 0.0001). Adjusted mean (standard error) difference in BP for the highest PTH quintile (59ng/l) was 5.9 (0.8) mm Hg for systolic BP and 4.5 (0.5) mm Hg for diastolic BP, compared with the lowest quintile (27ng/l). When both 25(OH)D and PTH were included in the same model, the associations of PTH with systolic and diastolic BP were unchanged. However, the associations between 25(OH)D and BP were attenuated, with mean (standard error) difference between the highest and lowest quintiles being 2.2 (0.6) mm Hg for systolic BP (P 0.01) and 0.8 (0.6) mm Hg for diastolic BP.ConclusionPTH may mediate most of the association between 25(OH)D and BP, which was not significant when also adjusting for body mass index. © 2011 American Journal of Hypertension, Ltd.