Relationship between urinary phosphate with cardiovascular disease and mortality in the ausdiab cohort.

Aim: To assess the association between urinary phosphate excretion and outcomes in a large population-based cohort. Background(s): Serum phosphate is associated with cardiovascular disease (CVD) and mortality in the general population. Greater dietary phosphorus intake may lead to higher serum phosphate and adverse outcomes. Urinary phosphate excretion is a marker of intestinal phosphorus absorption and may be a more reliable marker of phosphate homeostasis. Studies report good correlation between urine phosphate-creatinine ratio (uPiCr) and 24-hour urinary phosphate excretion, but whether uPiCr is associated with risk of CVD or mortality is uncertain. Method(s): Using the nationally representative AusDiab cohort, uPiCr was determined from available urine samples (n = 11,116). Participant baseline characteristics were compared across quartiles of uPiCr and regression analysis was used to determine associations. Relationships between uPiCr and all-cause mortality were determined using Cox proportion hazards regression with uPiCr modelled using fractional polynomials. Result(s): Mean age 51+/-14 y, 45% males and 9.6% chronic kidney disease (CKD-Epi equation). During a median follow-up 12.1 years there were 1265 deaths. Mean uPiCr was 1.45+/-0.7 mmol/mmol. Participants with higher uPiCr were older, more likely female, had higher albuminuria, lower GFR, greater prevalence of CVD and hypertension (all p < 0.001) and higher BMI (p = 0.002). With increasing quartiles of uPiCr the hazard ratios (HR) for all-cause mortality were 1.27 [95%CI 1.07,1.52], 1.54 [1.30,1.83], and 2.07 [1.76,2.44] (compared to the lowest quartile). When modelled as fractional polynomial, both low and high urine phosphate were independently associated with an increased risk of mortality. Conclusion(s): Low and high uPiCr is associated with increased all-cause mortality in a general population cohort and may serve as a useful marker for interventions aimed at improving phosphate balance.