Differences in association between hypoalbuminaemia and mortality among younger versus older patients on haemodialysis

ABSTRACT Background Ageing often affects biomarker production. Yet, clinical/optimal thresholds to guide clinical decisions do not consider this. Serum albumin decreases with age, but hypoalbuminaemia is defined as serum albumin <4.0 g/dl. This study explores whether age might affect serum albumin levels and its association with mortality in haemodialysis patients. Methods COSMOS (Current Management of Secondary Hyperparathyroidism: a Multicentre Observational Study) is a prospective, open-cohort, observational study of haemodialysis patients followed for 3 years. Binary logistic and linear regression were used to analyse the association between age and hypoalbuminaemia or serum albumin (continuous). Cox proportional hazard multivariate regression was used to examine the relationship between hypoalbuminaemia and mortality in patients younger and older than 65 years. Time-dependent receiver operating characteristic (ROC) curves were used to assess the discriminatory ability of serum albumin and optimal thresholds for predicting mortality. Results The present analysis included 5585 patients. The odds of experiencing hypoalbuminaemia increased with age [adjusted odds ratios = 1.56(95%CI: 1.31–1.86), 1.89(95%CI: 1.59–2.24), 2.68(95%CI: 2.22–3.23) for 56–65, 66–75, and >75 years, respectively (reference ≤55 years; P value for trend: <0.001)]. Survival analysis showed that the association between hypoalbuminaemia and mortality was weaker in patients aged ≥65 compared to <65 years [hazard ratios: 1.36(95%CI: 1.17–1.57) and 1.81(95%CI:1.42–2.31) respectively; P value for interaction 0.004]. The ability of albumin levels to predict mortality was consistently higher in younger patients. Optimal albumin thresholds for predicting mortality were 3.7 g/dl in patients younger than 65 years and 3.5 g/dl in patients 65 years and older. Conclusions Ageing is accompanied by lower albumin levels, and the association between hypoalbuminaemia and mortality may be modified by age. Different clinical thresholds that consider age may better discriminate risks associated with hypoalbuminaemia.