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

Abstract

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.

Conclusion: 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.

Keywords: Glomerular filtration rate; Muscle weakness; Proteinuria; Risk assessment.

Figure 1.

Flowchart of the study population. NHIS, National Health Insurance Service.

Figure 2.

Restricted cubic spline of odds ratios with 95% confidence intervals for lower-extremity dysfunction. The restricted cubic spline curve depicts the association between the estimated GFR and the odds of abnormal lower-extremity function, as calculated by both the Modification of Diet in Renal Disease (A) and chronic kidney disease Epidemiology Collaboration (B) equations. GFR, glomerular filtration rate.

Figure 3.

Restricted cubic spline of odds ratios with 95% confidence intervals for lower-extremity balance. The restricted cubic spline curve illustrates the relationship between the estimated GFR and the odds of abnormal lower-extremity balance, analyzed with the Modification of Diet in Renal Disease (A) and chronic kidney disease Epidemiology Collaboration (B) equations. GFR, glomerular filtration rate.

Figure 4.

Subgroup analysis of the association between GFR and abnormal lower-extremity function and between GFR and abnormal balance, stratified by sex. Forest plots showing ORs for abnormal lower-extremity function (A) and balance (B) stratified by sex. The ORs and 95% confidence intervals were calculated using multivariable logistic regression analysis. The ORs and 95% confidence intervals were calculated using multivariable logistic regression analysis, adjusted for income level, body mass index, hemoglobin level, smoking status, alcohol consumption, regular exercise status, hypertension, diabetes, dyslipidemia, ischemic heart disease, cerebrovascular disease, chronic obstructive pulmonary disease, depression, and the Charlson Comorbidity Index. OR, odds ratio; CI, confidence interval; MDRD, Modification of Diet in Renal Disease; GFR, glomerular filtration rate.