Validation and Comparison of Two Frailty Indexes: The MOBILIZE Boston Study

OBJECTIVES: To validate two established frailty indexes and compare their ability to predict adverse outcomes in a diverse, elderly, community-dwelling sample of men and women. DESIGN: Prospective observational study. SETTING: A diverse defined geographic area of Boston. PARTICIPANTS: Seven hundred sixty-five community-dwelling participants in the Maintenance of Balance, Independent Living, Intellect, and Zest in the Elderly Boston Study. MEASUREMENTS: Two published frailty indexes, recurrent falls, disability, overnight hospitalization, emergency department (ED) visits, chronic medical conditions, self-reported health, physical function, cognitive ability (including executive function), and depression. One index was developed from the Study of Osteoporotic Fractures (SOF) and the other from the Cardiovascular Health Study (CHS). RESULTS: The SOF frailty index classified 77.1% as robust, 18.7% as prefrail, and 4.2% as frail. The CHS frailty index classified 51.2% as robust, 38.8% as prefrail, and 10.0% as frail. Both frailty indexes (SOF; CHS) were similar in their ability to predict key geriatric outcomes such as recurrent falls (hazard ratio (HR)(frail)=2.2, 95% confidence interval (CI)=1.2-4.0; HR(frail)=1.9, 95% CI=1.2-3.1), overnight hospitalization (odds ratio (OR)(frail)=3.5, 95% CI=1.5-8.0; OR(frail)=4.4, 95% CI=2.4-8.2), ED visits (OR(frail)=3.5, 95% CI=1.4,8.8; OR(frail)=3.1, 95% CI=1.6-5.9), and disability (OR(frail)=5.4, 95% CI=2.3-12.3; OR(frail)=7.7, 95% CI=4.0-14.7), as well as chronic medical conditions, physical function, cognitive ability, and depression. CONCLUSION: Two established frailty indexes were validated using an independent elderly sample of diverse men and women; both indexes were good at distinguishing geriatric conditions and predicting recurrent falls, overnight hospitalization, and ED visits according to level of frailty. Although both indexes are good measures of frailty, the simpler SOF index may be easier and more practical in a clinical setting.