Moderate renal insufficiency at 70 years predicts mortality

Glomerular filtration rate (GFR) diminishes with age. Kidney function in the elderly is often assessed by serum creatinine alone, although it is insensitive in this age group. Formulae for predicting GFR are not widely used.

To study the effect of low predicted GFR on mortality.

Longitudinal cohort study.

The community-based Jerusalem Seventy Year Olds Longitudinal Study.

We studied 445 subjects, all aged 70 years, using questionnaires, a medical examination with history-taking, and standard laboratory tests. Moderate renal insufficiency was defined as a predicted GFR of <60 ml/min, based on the Cockcroft-Gault (CG) and the Modification of Diet in Renal Disease (MDRD) equations.

Predicted GFR was normally distributed, with a mean +/- SD of 62.4 +/- 15.27 ml/min. Predicted GFR was <60 ml/min in 221 (46%), most of whom had normal serum creatinine. Twelve-year mortality was 38.7% in these 221 vs. 27% in the other 204. The survival advantage was already evident after 3 years. Under Cox proportional hazard analysis using numerous common risk factors as independent variables, lower predicted GFR had a significant mortality risk (hazard ratio 2.108, 95%CI 1.43-3.12, p = 0.0002).

In community-dwelling elderly people, moderate renal insufficiency as assessed using the CG equation is a strong and independent predictor of mortality. Most of these at-risk patients have 'normal' serum creatinine.