MO515: Mortality Differences Between Men and Women With Chronic Kidney Disease in the Irish Health System: The National Kidney Disease Surveillance Programme

Abstract

BACKGROUND AND AIMS Chronic kidney disease is associated with higher mortality compared with the general population, but mortality differences between men and women with CKD are poorly understood. Although the prevalence of CKD is consistently higher in women than in men, emerging studies suggest that men experience poorer survival. The primary goal of this study was to compare mortality rates between men and women in the Irish health system and determine whether kidney function influenced these sex-specific risks. METHOD We created a cohort of 125 890 patients from the National Kidney Disease Surveillance System (NKDSS) to compare mortality rates between men and women. Patients were recruited from 1 January 2005 to 31 December 2010 and followed until 31 December 2013. Kidney function was determined using the CKD-EPI equation, generating estimated glomerular filtration rate (mL/min/1.73 m2) (eGFR). The primary outcome was all-cause mortality from national records provided by the Central Statistics Office (CSO). The principal exposure was participant sex, classified as men or women. Patients were censored at the date of initiation of dialysis or kidney transplantation, death, loss to follow-up or end of follow-up 31 December 2013. Mortality risks were compared using the Fine-Gray approach, which accounted for the competing risks of renal replacement therapy. Adjustments were made for baseline age, kidney function and blood biomarkers, which indicated the presence and severity of clinical disease. RESULTS Of the 125 890 participants, 55.1% were women, with a mean age of 54.1 (SD: 17.7) years. The median follow-up was 7.75 years (IQR: 6.33–8.55), 243 patients (0.19%) patients progressed to RRT and 14 179 patients (11.26%) died. Overall, mortality rates were significantly higher in men than in women (18.4 versus 16.6 deaths/1000 pyrs, respectively). Compared with women, men with CKD experienced significantly higher rates of death and RRT, P < .001 (Figure 1a). With each worsening GFR category, crude mortality rates increased by 18-fold in women compared with 9-fold in men. The P-value for the interaction of sex and GFR with mortality was <0.001. In stratified analyses, the magnitude of the sHR for men versus women decreased with each descending eGFR category from a peak of 2.17 (1.88–2.49) for eGFR >90 mL/min down to 1.21 (0.98–1.49) for eGFR <29 mL/min/1.72 m2 (Table 1) and was no longer significant in the eGFR <29 mL/min/1.72 m² category. CONCLUSION Although women have a higher burden of CKD than men in the Irish health system, the overall risks of death and RRT were far greater in men than in women. However, the excess risk in men diminished with increasing severity of kidney disease such that mortality risks for women approached those of men with advanced kidney disease. While these findings may have a biologic basis, fundamental disparities in care delivery, quality or accessibility between men and women is a far more likely explanation.