Serum calcium levels and hypertension among U.S. adults.

Serum calcium levels have been shown to be associated with cardiovascular disease (CVD); however, it is not clear whether serum calcium levels are related to hypertension, a risk factor for CVD. The authors examined the association between serum calcium and hypertension in a representative sample of US adults. A cross-sectional study of 12,405 third National Health and Nutrition Examination Survey participants 20 years and older was conducted. Serum total and ionized calcium levels were analyzed as quartiles. The main outcome of interest was hypertension (n=3437), defined as self-reported use of antihypertensive medication and/or systolic blood pressure ≥140 mm Hg or diastolic blood pressure ≥90 mm Hg. Elevated serum total calcium levels were positively associated with hypertension, independent of potential confounders including C-reactive protein, estimated glomerular filtration rate, serum albumin, 25(OH)D, and phosphorous. Compared with the lowest quartile of serum total calcium (referent category), the multivariable odds ratio (95% confidence interval) of hypertension was 1.49 (1.15-1.93) for the highest quartile (P=.005). This association persisted in subgroup analyses stratified by sex, age, and race-ethnicity. In contrast, serum ionized calcium levels were not associated with hypertension. Higher serum total calcium levels are positively associated with hypertension in a representative sample of U.S. adults.