Abstract and Introduction
Using a community-based cohort we studied the association between changes in the estimated glomerular filtration rate (eGFR) over time and the risk of all-cause mortality. We identified 529,312 adults who had at least three outpatient eGFR measurements over a 4-year period from a provincial laboratory repository in Alberta, Canada. Two indices of change in eGFR were evaluated: the absolute annual rate of change (in ml/min per 1.73 m2 per year) and the annual percentage change (percent/year). The adjusted mortality risk associated with each category of change in eGFR was assessed, using stable eGFR (no change) as the reference. Over a median follow-up of 2.5 years there were 32,372 deaths. Compared to the reference participants, those with the greatest absolute annual decline less than or equal to 5 ml/min per 1.73 m2 per year had significantly increased mortality (hazard ratio of 1.52) adjusted for covariates and kidney function at baseline (last eGFR measurement). Participants with the greatest increase in eGFR of 5 ml/min per 1.73 m2 per year or more also had significantly increased mortality (adjusted hazard ratio of 2.20). A similar pattern was found when change in eGFR was quantified as an annual percentage change. Thus, both declining and increasing eGFR were independently associated with mortality and underscore the importance of identifying change in eGFR over time to improve mortality risk prediction.
Studies have consistently demonstrated that more advanced chronic kidney disease (CKD) is associated with an increased risk of mortality across both general and high-risk populations.[1–5] However, these reports have predominantly considered kidney function at baseline, without consideration of how the change in kidney function over time influences the risk of such outcomes. There has been a growing interest in the association between change in kidney function and risk of adverse outcomes. Although population-based studies have reported an association between declining kidney function specifically and adverse clinical outcomes,[6–11] kidney function can be highly variable and improve over time in some patients.[10,12] Although recent studies have reported an association between improvements in kidney function (increasing estimated glomerular filtration rate (eGFR)) and risk of mortality,[7,8] these studies were limited by their select study population (CKD patients only) and small study size.[7,8]
Using a population-based cohort of individuals receiving routine clinical care in a single Canadian province, we investigated the association between changes in kidney function over time and risk of all-cause mortality. We explored change in kidney function using two indices: absolute annual rate of change and the annual percentage change. We hypothesized that both increasing and declining eGFR would be associated with higher mortality risk, as compared with stable kidney function.
Kidney Int. 2013;83(4):684-691. © 2013 Nature Publishing Group