Elevated relative mortality risk with mild-to-moderate chronic kidney disease decreases with age.

BACKGROUND: Renal disease is common in the general population and whilst few people progress to end-stage renal failure, mortality is increased. The aim of this study was to examine all-cause mortality risk in relation to chronic kidney disease (CKD) stages defined by estimated glomerular filtration rate (eGFR).
METHODS: Data were extracted from a computerized central laboratory system for a defined geographical area over a 3-year study period. The eGFR was calculated using the four-variable Modification of Diet in Renal Disease (MDRD) formula and aligned to the MDRD laboratory. Average annual mortality and relative risk (RR) of all-cause mortality was determined and compared for defined age and CKD bands.
RESULTS: 106 366 participants (55.5% female; 85% White, 13% South Asian, 2% Black and others) were eligible and studied, representing 49% of the Coventry adult population. 12 540 (12%) of the sample had some evidence of decreased kidney function, with an eGFR <60 ml/min/1.73 m2. 7611 (7%) participants died and there were significantly elevated risks of mortality with increasing renal dysfunction; RR = 4.0, 8.3, 16.2 and 43.5 for eGFR 45-59, 30-44, 15-29 and <15 ml/min/1.73 m2, respectively. Within age bands, RRs were statistically significantly raised with CKD progression and within CKD stage, RR of death decreased as age increased.
CONCLUSIONS: CKD prevalence increased with age and absolute and RR of mortality increased with progression of CKD. People aged over 75 years, with mild-to-moderate renal disease, representing 41% of this age group, have no increased RR of mortality. Further study of CKD and mortality, particularly progression over time and with respect to age is needed.