Association of CKD with disability in the United States.

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.