Validation of a Claims-Based Frailty Index Against Physical Performance and Adverse Health Outcomes in the Health and Retirement Study

BACKGROUND: A claims-based frailty index (CFI) was developed based on a deficit-accumulation approach using self-reported health information. This study aimed to independently validate the CFI against physical performance and adverse health outcomes. METHODS: This retrospective cohort study included 3,642 community-dwelling older adults who had at least 1 health care encounter in the year prior to assessments of physical performance in the 2008 Health and Retirement Study wave. A CFI was estimated from Medicare claims data in the past year. Gait speed, grip strength, and the 2-year risk of death, institutionalization, disability, hospitalization, and prolonged (>30 days) skilled nursing facility (SNF) stay were evaluated for CFI categories (robust: <0.15, prefrail: 0.15-0.24, mildly frail: 0.25-0.34, moderate-to-severely frail: ≥0.35). RESULTS: The prevalence of robust, prefrail, mildly frail, and moderate-to-severely frail state was 52.7%, 38.0%, 7.1%, and 2.2%, respectively. Individuals with higher CFI had lower mean gait speed (moderate-to-severely frail vs robust: 0.39 vs 0.78 m/s) and weaker grip strength (19.8 vs 28.5 kg). Higher CFI was associated with death (moderate-to-severely frail vs robust: 46% vs 7%), institutionalization (21% vs 5%), activity of daily living disability (33% vs 9%), instrumental activity of daily living disability (100% vs 22%), hospitalization (79% vs 23%), and prolonged SNF stay (17% vs 2%). The odds ratios per 1-SD (=0.07) difference in CFI were 1.46-2.06 for these outcomes, which remained statistically significant after adjustment for age, sex, and a comorbidity index. CONCLUSION: The CFI is useful to identify individuals with poor physical function and at greater risks of adverse health outcomes in Medicare data.