Physical Function and Mortality in Older Adults with Chronic Kidney Disease

Background Accurate mortality prediction can guide clinical care for older adults with CKD. Yet existing tools do not incorporate physical function, an independent predictor of death in older adults. We determined whether incorporating physical function measurements improve mortality prediction among older adults with CKD. Methods We included Chronic Renal Insufficiency Cohort participants who were 65 years and older, had eGFR <60 ml/min per 1.73 m2, not receiving kidney failure with replacement therapy (KFRT), and had least one gait speed assessment. Gait speed was measured at usual pace (>= 0.84, 0.83-0.65, 0.64-0.47, <= 0.46 m/s, or unable), and frailty was assessed using Physical Frailty Phenotype criteria (range 0-5 points, also known as Fried criteria). We modeled time to all-cause death over 5 years using Cox proportional hazard models, treating KFRT as censored and noncensored events in separate analyses. C-statistics assessed model discrimination. Results Among 2338 persons, mean age was 70 +/- 4 years, 43% were female, and 43% were Black. Mean eGFR was 42 +/- 13 ml/min per 1.73 m2, and median urine albumin-to-creatinine ratio was 33 mg/g (Q1 9, Q3 206). Over a median follow-period of 5 years, 392 died and 164 developed KFRT. In censored analyses, adding gait speed or frailty improved mortality risk prediction. The C-statistic changed from 0.69 to 0.72 with gait speed scores and from 0.70 to 0.73 with frailty scores. The performance of models with gait speed or frailty was similar in noncensored analyses. Conclusions Among older adults with CKD, adding measures of physical function modestly improves mortality prediction.