A predictive model for ADL dependence in community-living older adults based on a reduced set of cognitive status items

OBJECTIVE: To develop and validate a simple tool, based on a reduced set of Mini-Mental State Examination (MMSE) items, that can be used to predict the onset of ADL dependence, and to compare the predictive accuracy of this new tool with that of the MMSE. DESIGN: Two prospective, population-based cohort studies, in tandem. The predictive model developed in the initial cohort was subsequently validated in a separate cohort. SETTING: General community in New Haven, Connecticut. PARTICIPANTS: For the development cohort, 775 community-living persons, 72 years of age and older, who were independent at baseline in their ADL function. For the validation cohort, 1038 comparable subjects. MEASUREMENTS: All subjects underwent a baseline interview and cognitive assessment in their homes by a trained research nurse using standard instruments. Self-reported ADLs were ascertained at 1 year and 3 years for the development cohort and at 1 year and 21/2 years for the validation cohort. RESULTS: ADL dependence developed in 221 (28.5%) subjects in the development cohort. Although the rate of ADL dependence increased within each MMSE domain as the number of incorrect items increased, only orientation and short-term memory remained significantly associated with ADL dependence in multivariable analysis. A predictive model, based on the presence of impairments in these two domains, was developed that stratified subjects into three risk groups. Rates of ADL dependence were 22% (neither domain impaired), 44% (one domain impaired), and 68% (both domains impaired) (P<.001). The corresponding rates in the validation cohort, in which 191 (18.4%) subjects developed ADL dependence, were 15%, 26%, and 45% (P<.001). The area under the ROC curves for the MMSE and the reduced item strategy were nearly identical at 0.63 and 0.62, respectively. CONCLUSIONS: A simple and valid six-item strategy, based on the presence of impairments in orientation and short-term memory, predicts the onset of ADL dependence as effectively as does the 30-item MMSE. This new tool may be useful as part of a more comprehensive assessment when determining an older person's risk for developing ADL dependence.