Association of CKD with disability in the United States

Abstract

Background: Little is known about disability in early-stage chronic kidney disease (CKD).

Study design: Cross-sectional national survey (National Health and Nutrition Examination Survey 1999-2006).

Setting & participants: Community-based survey of 16,011 noninstitutionalized US civilian adults (aged ≥20 years).

Predictor: CKD, categorized as no CKD, stages 1 and 2 (albuminuria and estimated glomerular filtration rate [eGFR] ≥60 mL/min/1.73 m²), and stages 3 and 4 (eGFR, 15-59 mL/min/1.73 m²).

Outcome: Self-reported disability, defined by limitations in working, walking, and cognition and difficulties in activities of daily living (ADL), instrumental ADL, leisure and social activities, lower-extremity mobility, and general physical activity.

Measurements: Albuminuria and eGFR assessed from urine and blood samples; disability, demographics, access to care, and comorbid conditions assessed using a standardized questionnaire.

Results: Age-adjusted prevalence of reported limitations generally was significantly greater with CKD: for example, difficulty with ADL was reported by 17.6%, 24.7%, and 23.9% of older (≥65 years) and 6.8%, 11.9%, and 11.0% of younger (20-64 years) adults with no CKD, stages 1 and 2, and stages 3 and 4, respectively. CKD also was associated with greater reported limitations and difficulty in other activities after age adjustment, including instrumental ADL, leisure and social activities, lower-extremity mobility, and general physical activity. Other demographics, socioeconomic status, and access to care generally only slightly attenuated the observed associations, particularly in older individuals; adjustment for cardiovascular disease, arthritis, and cancer attenuated most associations such that statistical significance no longer was achieved.

Limitations: Inability to establish causality and possible unmeasured confounding.

Conclusion: CKD is associated with a higher prevalence of disability in the United States. Age and other comorbid conditions account for most, but not all, of this association.