Outcomes associated with serum phosphorus level in males with non-dialysis dependent chronic kidney disease.

BACKGROUND/AIMS: Hyperphosphatemia is associated with higher mortality and increased incidence of end-stage renal disease in patients with non-dialysis dependent CKD (NDD-CKD), but there has not been a concomitant assessment of mortality and progressive kidney disease that would also account for cumulative effects of hyperphosphatemia.

METHODS: In order to account for the cumulative effects of abnormal serum phosphorus we examined associations of not only baseline, but also time-averaged serum phosphorus levels with all-cause mortality, the composite of mortality or ESRD and the slopes of estimated glomerular filtration rate (eGFR), by using Cox models and mixed effects models in a contemporary cohort of 713 males with moderate and advanced NDD-CKD.

RESULTS: Higher baseline and time-averaged serum phosphorus were both associated with mortality and with the composite outcome. A 1 mg/dl higher time-averaged serum phosphorus was associated with a multivariable adjusted hazard ratio of all-cause mortality (95% CI) of 1.56 (1.19 - 2.05), p = 0.001. Higher serum phosphorus was associated with a steeper slope of eGFR in unadjusted analyses, but this association became non-significant after multivariable adjustments.

CONCLUSION: The cumulative burden of hyperphosphatemia is associated with increased mortality in patients with moderate and advanced NDD-CKD. Clinical trials are needed to determine if lowering serum phosphorus can result in improved mortality in this population.