Abstract
BackgroundHyperphosphataemia is linked to cardiovascular disease and mortality in chronic kidney disease (CKD). Outcome in CKD is also affected by socioeconomic status. The objective of this study was to assess the associations between serum phosphate, multiple deprivation and outcome in CKD patients.MethodsAll adult patients currently not on renal replacement therapy (RRT), with first time attendance to the renal outpatient clinics in the Glasgow area between July 2010 and June 2014, were included in this prospective study. Area socioeconomic status was assessed as quintiles of the Scottish Index of Multiple Deprivation (SIMD). Outcomes were all-cause and cardiovascular mortality and commencement of RRT.ResultsThe cohort included 2950 patients with a median (interquartile range) age 67.6 (53.6–76.9) years. Median (interquartile range) eGFR was 38.1 (26.3–63.5) ml/min/1.73 m2, mean (±standard deviation) phosphate was 1.13 (±0.24) mmol/L and 31.6 % belonged to the most deprived quintile (SIMD quintile I). During follow-up 375 patients died and 98 commenced RRT. Phosphate ≥1.50 mmol/L was associated with all-cause (hazard ratio (HR) 2.51; 95 % confidence interval (CI) 1.63-3.89) and cardiovascular (HR 5.05; 95 % CI 1.90–13.46) mortality when compared to phosphate 0.90–1.09 mmol/L in multivariable analyses. SIMD quintile I was independently associated with all-cause mortality. Phosphate did not weaken the association between deprivation index and mortality, and there was no interaction between phosphate and SIMD quintiles. Neither phosphate nor SIMD predicted commencement of RRT.ConclusionsMultiple deprivation and serum phosphate were strong, independent predictors of all-cause mortality in CKD and showed no interaction. Phosphate also predicted cardiovascular mortality. The results suggest that phosphate lowering should be pursued regardless of socioeconomic status.
Highlights
Hyperphosphataemia is linked to cardiovascular disease and mortality in chronic kidney disease (CKD)
Phosphate ≥1.50 mmol/L was a predictor of death irrespective of Scottish Index of Multiple Deprivation (SIMD) quintile, and the most deprived SIMD quintile was only borderline significantly associated with mortality in this model. In this large cohort of CKD patients not established on renal replacement therapy (RRT), we found that higher phosphate was an independent predictor of all-cause and cardiovascular mortality
Serum phosphate was significantly higher in patients from the most deprived compared to the least deprived areas, but the association between phosphate and mortality was not altered by deprivation, and there was no interaction between these two variables for the prediction of any endpoint
Summary
Hyperphosphataemia is linked to cardiovascular disease and mortality in chronic kidney disease (CKD). Independent associations between serum phosphate and cardiovascular and all-cause mortality have been shown among persons on chronic dialysis [2, 3] and in nondialysis CKD patients [4,5,6]. The risk of adverse outcome in CKD, such as CKD progression [17, 18] and mortality [19, 20], is increased in patients with lower socioeconomic status. These associations are only partly explained by the high rates of traditional cardiovascular and renal risk factors observed in these groups [21,22,23]. Factors characterising deprivation and having an unfavourable impact on health outcome [24] may vary between geographical
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