Socioeconomic position and all-cause death in patients treated with maintenance dialysis: a cohort study of causal pathways

Abstract

INTRODUCTION: Patients with kidney failure treated with maintenance dialysis from low socioeconomic position (SEP) experienced a higher risk of mortality and morbidities. However, the mechanisms involved are unknown. This study aimed to elucidate the causal pathways between SEP, all-cause, and cause-specific mortality in patients treated with dialysis. We aimed to examine whether multimorbidity and remoteness mediate the association between SES and mortality on dialysis in incident patients with treated kidney failure. METHODS: This cohort study included all adult patients with kidney failure aged 18 years or over who commenced peritoneal dialysis or haemodialysis in Australia between 2005 and 2019. Using data from the Australia and New Zealand Dialysis and Transplant (ANZDATA) registry, we defined SEP as deciles and categorised into less than six and six and more. The association between SEP and all-cause mortality on dialysis was examined using adjusted Cox regression and competing risk models, with kidney transplantation considered as a censored event or as a competing event, respectively. Mediation analysis examined other factors including remoteness and multicomorbidities such as diabetes and vascular disease) mediated the association between SEP and death. RESULTS: There were 37,929 incident patients with kidney failure who initiated dialysis in Australia between 2005 and 2019, with a median (IQR) patient follow-up period of 4.0 (2.0, 7.1) years. Of these, 20,597 (54%) patients were from low SES. Patients from low SES were younger and a greater proportion of patients had diabetes (53% vs. 45%, p=<0.001) and prevalent vascular disease (50% vs. 47%, p= p=<0.001) and resided in remote areas (8.7% vs. 3.5%, p=<0.001) compared to patients from high SES. Compared to patients from low SES, the adjusted HR and sub-distribution HR (95%CI) for all-cause mortality in patients from high SES (95%CI) was 0.94 (0.910 0.969) and xxx, respectively. Other covariates associated with an increased risk of all-cause mortality were geographical remoteness, ethnicity, age, gender, diabetes, and PVD. The proportions of the effect between SES and all-cause mortality on dialysis mediated by remoteness, diabetes, and prevalent vascular disease were 23.74, 16, and 11.80%, respectively. CONCLUSIONS: Remoteness, diabetes, and vascular disease mediated over 50% of the association between low SES and high risk of death on dialysis in incident patients with kidney failure. These findings suggest that a greater focus on the understanding and approaches to the management of these mediators may improve the socioeconomic inequity in health between patients with kidney failure from low and high SES backgrounds. I have no potential conflict of interest to disclose.