Calcium intake and blood pressure in elderly women.

Abstract

The authors studied the relative importance of calcium intake as a correlate of blood pressure in a cross-sectional analysis of 6,517 nonblack women aged > or = 65 years from Portland, Oregon; Minneapolis, Minnesota; Baltimore, Maryland; and the Monongahela Valley near Pittsburgh, Pennsylvania, who enrolled in the Study of Osteoporotic Fractures in 1986. Dietary calcium intake was measured by using a modified food frequency questionnaire. There were weak associations between total calcium intake and blood pressure, such that each 1,000 mg/day increase in calcium intake was associated with a 1.5 mmHg decrease in systolic blood pressure (95% confidence interval -2.2 to -0.8, p < 0.0001) and a 0.5 mmHg decrease in diastolic pressure (95% confidence interval -0.8 to -0.20, p < 0.004). After adjustment for confounding variables, total calcium intake continued to have a weak inverse association only with diastolic blood pressure. The multivariate models revealed several stronger independent risk factors for blood pressure, including age, body mass index, alcohol consumption, and level of education (all p < 0.01). The small size of the inverse association between calcium intake and blood pressure limits its biological importance in this population of elderly women.