Association between worsening renal function severity during hospitalization and low physical function at discharge: a retrospective cohort study of older patients with heart failure and chronic kidney disease from Japan

Abstract

Background: The number of hospitalized older patients with chronic heart failure, chronic kidney disease, and worsening renal function is rising in Japan. This study aimed to clarify the impact of the severity of worsening renal function during hospitalization on low physical function at discharge of these patients.

Methods: We included 573 consecutive heart failure patients who underwent phase I cardiac rehabilitation. Worsening renal function severity was defined according to elevation during hospitalization of baseline serum creatinine on admission: non-worsening renal function, serum creatinine < 0.2 mg/dL; worsening renal function II/I, serum creatinine ≥ 0.2 to < 0.5 mg/dL; worsening renal function III, and serum creatinine ≥ 0.5 mL/dL. Physical function was measured with the Short Performance Physical Battery. We compared background factors, clinical parameters, pre-hospitalization walking levels, Functional Independence Measure score, and physical function in the three renal function groups. Multiple regression analysis was performed with the Short Performance Physical Battery at discharge as the dependent variable.

Results: The final analysis included 196 patients (mean age 82.7 years, male 51.5%) categorized into three groups based on worsening renal function: worsening renal function grade III group (n = 55), worsening renal function grade II/I group (n = 36), and non-worsening renal function group (n = 105). There is no significant difference in walking levels before hospitalization between the three groups, but physical function at discharge was significantly lower in the worsening renal function III group. Moreover, worsening renal function III was an independent factor for low physical function at discharge.

Conclusion: Worsening of renal function during hospitalization in older patients with heart failure and chronic kidney disease was strongly associated with low physical function at discharge, even after adjusting for other potentially confounding factors, such as pre-hospitalization walking levels, walking start day, and Geriatric Nutrition Risk Index at discharge. Notably, worsening renal function of mild or moderate severity (grade II/I) did not show a significant association with low physical function.

Keywords: Indoxyl sulfate; Mitochondrial dysfunction; Older patients with heart failure and chronic kidney disease; Physical function; Sarcopenia; Severity of worsening renal function.