Racial Differences in Association of Serum Calcium with Mortality and Incident Cardio- and Cerebrovascular Events

Abstract

Context: Abnormalities in calcium metabolism may potentially contribute to the development of vascular disease. Calcium metabolism may be different in African American (AA) vs white individuals, but the effect of race on the association of serum calcium with clinical outcomes remains unclear. Objective: This study sought to examine race-specific associations of serum calcium levels with mortality and with major incident cardiovascular events. Design and Setting: This was a historical cohort study in the U.S. Department of Veterans Affairs health care facilities. Participants: Participants included veterans (n = 1 967 622) with estimated glomerular filtration rate ≥ 60 mL/min/1.73 m2. Main Outcome Measures: The association between serum calcium levels with all-cause mortality, incident coronary heart disease (CHD), and ischemic stroke incidence was examined in multivariable adjusted Cox proportional hazards models, including an interaction term for calcium and race. Results: The association of calcium with all-cause mortality was U-shaped in both AA and white patients, but race modified the association of calcium with all-cause mortality. Compared with white patients, AA patients experienced lower risk of mortality when calcium was ≥ 8.8 mg/dL, with a statistically significant interaction (P < .001). Conversely, AA vs white race was associated with higher mortality when calcium was < 8.8 mg/dL. Calcium showed no significant association with ischemic stroke or CHD in both races; and race did not modify these associations (P = .37 and 0.11, respectively for interaction term). Conclusions: Race modified the U-shaped association between calcium and all-cause mortality. Serum calcium is not associated with incident stroke or CHD in either AA or white patients. The race-specific difference in the association of calcium levels with mortality warrants further examination.