Normal aging results in a predictable decrease in glomerular filtration rate (GFR), and low GFR is associated with worsened survival. If this survival disadvantage is directly caused by the low GFR, as opposed to the disease causing the low GFR, the risk should be similar regardless of the underlying mechanism. Our objective was to determine if age-related decreases in estimated GFR (eGFR) carry the same prognostic importance as disease-attributable losses in patients with ventricular dysfunction. We analyzed the Studies Of Left Ventricular Dysfunction limited data set (n = 6,337). The primary analysis focused on determining if the eGFR-mortality relation differed by the extent to which the eGFR was consistent with normal aging. Mean eGFR was 65.7 ml/min/1.73 m(2) (SD = 19.0). Across the range of age in the population (27 to 80 years), baseline eGFR decreased by 0.67 ml/min/1.73 m(2)/year (95% confidence interval [CI] 0.63 to 0.71). The risk of death associated with eGFR was strongly modified by the degree to which the low eGFR could be explained by aging (p for interaction <0.0001). For example, in a model incorporating the interaction, uncorrected eGFR was no longer significantly related to mortality (adjusted hazard ratio 1.0 per 10 ml/min/1.73 m(2), 95% CI 0.97 to 1.1, p = 0.53), whereas a disease-attributable decrease in eGFR above the median carried significant risk (adjusted hazard ratio 2.8, 95% CI 1.6 to 4.7, p <0.001). In conclusion, in the setting of left ventricular dysfunction, renal dysfunction attributable to normal aging had a limited risk for mortality, suggesting that the mechanism underlying renal dysfunction is critical in determining prognosis.
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