Relationship between renal function and physical performance in elderly hospitalized patients

Chronic kidney disease (CKD) is increasingly recognized as a cause of worsening physical functioning in older patients. The Short Physical Performance Battery (SPPB) is highly reliable in older populations, but no data on older hospitalized patients with different degrees of kidney function are available. We aimed at testing the association between estimated glomerular filtration rate (eGFR) and SPPB, either global score (range 0-12) or its individual components (muscle strength, balance, and walking speed, each ranging from 0 to 4), in a sample of older hospitalized patients. Our series consisted of 486 patients aged 65 or more consecutively enrolled in 11 acute care medical wards participating to a multicenter observational study. eGFR was obtained by the Chronic Kidney Disease Epidemiological Collaboration (CKD-EPI) equation. Physical performance was objectively measured by the SPPB. The relationship between eGFR and SPPB was investigated by multiple linear regression analysis. Physically impaired patients (SPPB total score<5) were older, had lower serum albumin and Mini-Mental State Examination (MMSE) scores as well as higher overall co-morbidity, prevalence of stroke, cancer, and anemia compared to those with intermediate (SPPB=5-8) and good physical performance (SPPB=9-12). Fully adjusted multivariate models showed that eGFR (modeled as 10 mL/min per 1.73 m(2) intervals) was independently associated with the SPPB total score (B=0.49; 95% confidence interval [CI]=0.18-0.66; p=0.003), balance (B=0.30; 95% CI=0.10-0.49; p=0.005), and muscle strength (B=0.06; 95% CI=0.01-0.10; p=0.043), but not with walking speed (B=-0.04; 95% CI=-0.09-0.11; p=0.107). In conclusion, reduced renal function is associated with poorer physical performance in older hospitalized patients. SPPB is worthy of testing to monitor changes in physical performance in elderly CKD patients.