Calcium, phosphorus, parathyroid hormone, and cardiovascular disease in hemodialysis patients: The USRDS waves 1, 3, and 4 study

Animal studies suggest that calcium-phosphorus homeostatic abnormalities cause cardiovascular disease in uremia; few observational studies in humans have explored this. Associations in the retrospective United States Renal Data System Waves 1, 3, and 4 Study of 14,829 patients who were on hemodialysis on December 31, 1993, were examined. Mean age and duration of renal replacement therapy were 60.0 and 3.2 yr, respectively; 40.7% had diabetes. Quintiles (Q₁ to Q₅) of (albumin-adjusted) calcium were ≤8.7, 8.8 to 9.2, 9.3 to 9.6, 9.7 to 10.2, and >10.2 mg/dl; phosphorus, ≤4.4, 4.5 to 5.3, 5.4 to 6.3, 6.4 to 7.5, and >7.5 mg/dl; calcium-phosphorus product, ≤40.9, 41.0 to 50.1, 50.2 to 59.2, 59.3 to 71.0, and >71.0 mg ²/dl²; and parathyroid hormone (PTH), ≤37, 38 to 99, 100 to 210, 211 to 480, and >480 pg/ml. Higher calcium levels were associated with fatal or nonfatal cardiovascular events (adjusted hazards ratio, 1.08 for Q₅, versus Q₁) and all-cause mortality (Q₂, 1.07; Q₄, 1.11; Q₅, 1.14). Phosphorus levels were associated with cardiovascular events (Q₂, 1.06; Q₃, 1.13; Q₄, 1.14; Q₅, 1.25) and mortality (Q₄, 1.10; Q₅, 1.19), calcium-phosphorus product was associated with cardiovascular events (Q₃, 1.09; Q₄, 1.14; Q₅, 1.24) and mortality (Q₄, 1.09; Q₅, 1.19), and PTH levels were associated with cardiovascular events (Q₅, 1.12) and mortality (Q₅, 1.17). Despite limitations (including retrospective design; noncurrent study era; and lack of serial calcium, phosphorus, and PTH measurements), this study suggests that disorders of calcium homeostasis are associated with fatal and nonfatal cardiovascular events and all-cause mortality in hemodialysis patients.