Development and Validation of an Index to Predict Activity of Daily Living Dependence in Community-Dwelling Elders

Abstract

Maintaining independence in daily functioning is an important health outcome in older adults. A key measure of functional independence in elders is the ability to do activities of daily living (ADL) without the assistance of another person. However, few prognostic indices have been developed that stratify elders into groups at variable risk for developing ADL dependence. We sought to develop and validate a prognostic index that distinguishes between elders at different risk of ADL dependence. We studied subjects enrolled in Asset and Health Dynamics Among the Oldest Old (AHEAD), a nationally representative cohort of elders older than the age of 70. We included 5239 subjects (mean age, 77) reporting that they could do each of 5 ADL (bathing, dressing, toileting, transferring, and eating) without the assistance of another person at baseline. Subjects were divided into development (n = 3245) and validation (n = 1994) samples based on region of the United States. Our primary outcome was the need for help (dependence) with at least one ADL at 2 years. We used logistic regression to select among predictor variables encompassing several domains: demographic characteristics, comorbid conditions, functional status, cognitive status, and general health indicators. The 9 independent predictors of 2-year ADL dependence were age older than 80, diabetes, difficulty walking several blocks, difficulty bathing or dressing, need for help with personal finances, difficulty lifting 10 pounds, inability to name the Vice President, history of falling, and low body mass index. We created a risk score by assigning 1 point to each risk factor. In the development sample, rates of 2-year ADL dependence in subjects with 0, 1, 2, 3, 4, and 5 or more risk factors were 1.3%, 2.8%, 3.8%, 10%, 22%, and 33%, respectively (P < 0.001, roc area = 0.79). In the validation sample, the rates were 0.7%, 4.3%, 8.7%, 11%, 18%, and 40% (P < 0.001, roc area = 0.77). The risk score also discriminated between subjects at variable risk for a combined outcome of either ADL decline or death (4.3%, 7.6%, 15%, 21%, 30%, and 47%). Using data available from patient reports, we validated a simple risk index that distinguished between elders at variable risk of ADL dependence. This index may be useful for identifying elders at high risk of poor outcomes or for risk adjustment.