Increased risk of mortality in the elderly population with late-stage chronic kidney disease: a cohort study in Taiwan

Background. Taiwan has the world's highest incidence and second highest prevalence of end-stage renal disease (ESRD), particularly in older age groups. However, the transition from chronic kidney disease (CKD) to death or ESRD remains unclear. This study aimed to investigate the impact of late-stage CKD on all-cause and cause-specific mortality by identifying the CKD population. Methods. This was an observational cohort study (n = 35 529), mean age 75.7 years (SD = 5.3), of participants in the Elderly Health Examination Program (EHEP) in Kaohsiung City, Taiwan, between 2002 and 2004. Estimated glomerular filtration rate (eGFR) was calculated by the simplified modified diet in renal disease equation. Proportional hazard ratios (HR) of mortality associated with late-stage CKD were assessed by Cox regression. Results. The crude prevalence rate of CKD stages 3-5 was 39.4%; 1840 participants (5.18%) died within 2-year follow-up, a mortality rate of 20.3 per 1000 person-years overall and 16.4 per 1000 person-years in the reference group. Higher HR for all-cause and cause-specific mortality were found in the groups with decreased eGFR. Compared with the reference group (eGFR > 60 mL/min/1.73 m(2)), adjusted HR for all-cause mortality were 1.5, 2.1 and 2.6 for groups with eGFR 30-44, 15-29 and < 15 mL/min/ 1.73 m(2), respectively (P < 0.001). Higher HR of mortality due to cardiovascular or renal diseases were also significantly associated with decreased eGFR (P < 0.05). Conclusion. Late-stage CKD is a significant risk factor for mortality, especially due to cardiovascular and renal diseases, in elderly Taiwanese. Given the higher prevalence rate of late-stage CKD in the study area, CKD patient mortality was relatively lower, which might reflect underestimation of renal function for patients at early stages of CKD, or partly explain the high ESRD population.