Longitudinal assessment of patient dependence in Alzheimer disease

Background: The Dependence Scale measures the amount of assistance patients with dementia require in performing daily activities. Validity and reliability of this scale have been demonstrated, but the progression throughout long periods in patients with Alzheimer disease (AD) has not previously been examined. Objective: To determine the longitudinal course of patient dependence in a cohort of prospectively followed AD patients. Methods: Two hundred thirty AD patients enrolled in the Predictors Study were followed up prospectively at 6-month intervals for an average of 6.5 visits. The Dependence Scale was administered to a caregiver, and patients were assessed with the modified Mini-Mental State Examination (mMMSE) and the Blessed Dementia Rating Scale. Dependence level and the additive sum of the Dependence Scale items were considered for analysis. Results: Generalized estimating equations to regression analyses were used to determine that both Dependence Scale scores and dependence level significantly decline with time. By covarying mMMSE scores and self-care deficits factor scores of the Blessed Dementia Rating Scale, generalized estimating equations analysis also demonstrated that change in patient dependence was independent of global cognitive decline and other measures of activities of daily living, respectively. Conclusions: This study shows the validity of the Dependence Scale and demonstrated that dependency in AD significantly declines with time independent of global cognition and other self-care deficits. The scale is a valuable instrument for outcomes research, efficacy trials, and behavioral research in AD.