Relations of Serum Phosphorus and Calcium Levels to the Incidence of Cardiovascular Disease in the Community

Abstract

BACKGROUND: Higher levels of serum phosphorus and the calcium-phosphorus product are associated with increased mortality from cardiovascular disease (CVD) in patients with chronic kidney disease (CKD) or prior CVD. However, it is unknown if serum phosphorus levels influence vascular risk in individuals without CKD or CVD. METHODS: We prospectively evaluated 3368 Framingham Offspring study participants (mean age, 44 years; 51% were women) free of CVD and CKD. We used multivariable Cox models to relate serum phosphorus and calcium levels to CVD incidence. RESULTS: On follow-up (mean duration, 16.1 years), there were 524 incident CVD events (159 in women). In multivariable analyses and adjusting for established risk factors and additionally for glomerular filtration rate and for hemoglobin, serum albumin, proteinuria, and C-reactive protein levels, a higher level of serum phosphorus was associated with an increased CVD risk in a continuous fashion (adjusted hazard ratio per increment of milligrams per deciliter, 1.31; 95% confidence interval, 1.05-1.63; P=.02; P value for trend across quartiles = .004). Individuals in the highest serum phosphorus quartile experienced a multivariable-adjusted 1.55-fold CVD risk (95% confidence interval, 1.16%-2.07%; P=.004) compared with those in the lowest quartile. These findings remained robust in time-dependent models that updated CVD risk factors every 4 years and in analyses restricted to individuals without proteinuria and an estimated glomerular filtration rate greater than 90 mL/min per 1.73 m(2). Serum calcium was not related to CVD risk. CONCLUSION: Higher serum phosphorus levels are associated with an increased CVD risk in individuals free of CKD and CVD in the community. These observations emphasize the need for additional research to elucidate the potential link between phosphorus homeostasis and vascular risk.