Hyperphosphatemia is associated with anemia in adults without chronic kidney disease: results from the National Health and Nutrition Examination Survey (NHANES): 2005–2010

BACKGROUND: Hyperphosphatemia, serum phosphorus ≥ 4.4 mg/dL, is associated with increased risk for chronic kidney disease and cardiovascular disease. Previous studies have shown a weak association between dietary phosphorus intake and serum phosphorus concentrations. While much less common in the general population, hypophosphatemia (< 2.5 mg/dL) may be associated with metabolic syndrome and obesity. METHODS: Using three cycles from the National Health and Nutrition Examination Survey (NHANES) (2005–2010), this study evaluated independent risk factors for hyperphosphatemia and hypophosphatemia. RESULTS: Risk factors for hyperphosphatemia included higher adjusted calcium (OR 2.90, 95% CI 2.43-3.45), increasing cholesterol (OR 1.003, 95% CI 1.001-1.005), female gender (OR 1.61, 95% CI 1.39-1.87) and low hemoglobin (OR 1.52, 95% CI 1.17-1.98). Advanced age was protective (OR 0.98, 95% CI 0.977-0.987). Models that included fasting serum glucose found lower body mass index (BMI) to be protective (OR 0.97, 95% CI 0.96-0.99) and adjusting for serum vitamin D and parathyroid hormone removed the association with low hemoglobin and BMI. Risk factors for hypophosphatemia included the following protective factors: higher albumin (OR 0.56, 95% CI 0.35-0.93), higher BUN (OR 0.90, 95% CI 0.86, 0.95), corrected calcium (OR 0.38, 95% CI 0.23-0.63) and female gender (OR 0.47, 95% 0.24-0.94). In men, higher fasting glucose levels increased risk (OR 1.01, 95% CI 1.0004-1.01). CONCLUSION: This study is the first to show an association between low hemoglobin levels and increased risk for hyperphosphatemia among individuals without chronic kidney disease. We did not find any association between diabetes mellitus, increasing BMI or fasting glucose levels and hypophosphatemia.