Effects of cognitive performance on change in physical function in long-stay nursing home residents

Determining the nature and rate of change in physical function among long-stay nursing home (NH) residents classified by cognitive performance is needed to inform judgments about prognosis and design of clinical trials to minimize functional decline. The study consisted of a longitudinal analysis using random coefficients models of 71,388 noncomatose residents aged 65 and older admitted in one of five states participating in the Health Care Financing Administration-sponsored National Case Mix and Quality Demonstration Project who stayed in the nursing home 1 year or longer. Linear effects of cognitive impairment on admission and over time on the trajectory of dependence in activities of daily living (ADLs) were estimated, adjusting for demographic status upon admission. Interaction terms were used to determine if subgroups of residents at the same cognitive level were at risk for a steeper than average rate of decline. Measures were derived from the NH Minimum Data Set (MDS+) ratings of each domain. Cognition was measured using the MDS-Cognitive Performance Scale. Physical function was determined by summing ADL dependence ratings of bathing, dressing, grooming, toileting, and eating (range 0 to 20). Demographics included age, gender, race, and marital status. On average, ADL dependence worsened 0.84 points per year among these long-stay residents. Only cognition and marital status had clinically significant effects on ADL dependence. Married residents exhibited more ADL dependence than unmarried residents. Severity of cognitive impairment on admission and over time influenced severity of ADL dependence but not rate of decline. No interaction terms were clinically significant. Clinicians seeking to identify factors that accelerate ADL decline in long-stay NH residents must examine explanatory variables other than cognitive impairment and demographics.