Urinary Creatinine Excretion Rate and Mortality in Persons With Coronary Artery Disease

Abstract

Background— In persons with coronary artery disease, low body mass index is associated with greater mortality; however, it is uncertain whether low muscle mass is a risk factor for mortality in this setting. Methods and Results— In this study, 903 individuals with coronary artery disease provided 24-hour urine collections. We measured urine creatinine and volume and calculated creatinine excretion rate, a marker of muscle mass. Cox proportional-hazards models evaluated the association of creatinine excretion rate with mortality risk. Over a median follow-up of 6.0 years, 232 participants (26%) died. Compared with the highest sex-specific creatinine excretion rate tertile, the lowest tertile (<1068 mg/d in men, <766 mg/d in women) was associated with >2-fold risk of mortality (hazard ratio, 2.30; 95% confidence interval, 1.51 to 3.51) in models adjusted for age, sex, race, cystatin C–based estimated glomerular filtration rate, body mass index, traditional cardiovascular disease risk factors, and C-reactive protein levels. The association was essentially unaltered with further adjustment for physical fitness, left ventricular mass, left ventricular ejection fraction, or fasting insulin and glucose levels. Conclusions— Lower creatinine excretion rate is strongly associated with mortality in outpatients with coronary artery disease, independently of conventional measures of body composition, kidney function, and traditional coronary artery disease risk factors. Future studies should determine whether low creatinine excretion rate may be a modifiable risk factor for mortality among persons with coronary artery disease, potentially through resistive exercise training or nutrition interventions.