Association of kidney function and proteinuria with lower-extremity dysfunction in older Korean adults: a cross-sectional study.

Background/aims: Chronic kidney disease (CKD) is associated with complications that affect physical function and mobility. This study investigated the associations between kidney function, proteinuria, and lower-extremity dysfunction.

Methods: Data were obtained from the Korean National Health Insurance Service Health Screening Program, including individuals aged 66 years who participated in the National Screening Program for Transitional Ages in Korea. Participants were stratified based on estimated glomerular filtration rate (eGFR) into four groups: Group 1 (eGFR ≥ 90 mL/min/1.73 m2), Group 2 (60 ≤ eGFR < 90 mL/min/1.73 m2), Group 3 (30 ≤ eGFR < 60 mL/min/1.73 m2), and Group 4 (eGFR < 30 mL/min/1.73 m2). Lower-extremity dysfunction was assessed using two physical tests measuring function and balance. Multivariable logistic regression was performed to examine the associations between kidney function, proteinuria, and lower-extremity dysfunction.

Results: Group 2 served as the reference. Both decreased (Groups 3 and 4) and elevated (Group 1) eGFR levels were significantly associated with an increased risk of lower-extremity dysfunction (Group 4: adjusted OR 1.40, 95% CI 1.10-1.78; Group 1: adjusted OR 1.19, 95% CI 1.12-1.25). Similar patterns were observed for balance dysfunction. A U-shaped relationship was identified between eGFR and lower-extremity dysfunction. Proteinuria was independently associated with balance dysfunction (adjusted OR 1.35, 95% CI 1.20-1.51) but not with lower-extremity dysfunction.

Conclusions: A U-shaped relationship was identified between renal function and lower-extremity dysfunction, with both lower and elevated eGFR linked to increased risks of impairment, underscoring the need for regular assessment of lower-extremity function and appropriate interventions in patients with CKD, elevated eGFR, or proteinuria.