Change in a Claims-Based Frailty Index, Mortality, and Health Care Costs in Medicare Beneficiaries

Background A claims-based frailty index (CFI) allows measurement of frailty on a population scale. Our objective was to examine the association of changes in CFI over 12 months with mortality and Medicare costs. Methods We used a 5% sample of fee-for-service Medicare beneficiaries. We estimated CFI (range: 0-1; nonfrail [<0.20], mildly frail [0.20-0.29], moderately-to-severely frail [>= 0.35]) on January 1, 2015 and January 1, 2016. Beneficiaries were categorized as having a large decrease (-<0.045), small decrease (-<= 0.045-0.015), stable (+/- 0.015), small increase (>0.015-0.045), or large increase (>0.045). We used Cox proportional hazards model to estimate hazard ratio (HR) for mortality adjusting for age, sex, and 2015 CFI value and compared total Medicare costs from January 1, 2016 to December 31, 2016. Results The study population included 995 664 beneficiaries (mean age 77 years, 56.8% female). In nonfrail (n = 906 046), HR (95% confidence interval [CI]) ranged from 0.71 (0.67-0.75) for a large decrease to 2.75 (2.68-2.33) for a large increase. In moderate-to-severely frail beneficiaries (n = 16 527), the corresponding HR (95% CI) ranged from 0.63 (0.57-0.70) to 1.21 (1.06-1.38). The mean total Medicare cost per member per year (standard deviation) was from $12 149 ($83 508) in nonfrail beneficiaries to $61 155 ($345 904) in moderate-to-severely frail beneficiaries. Conclusions One-year changes in CFI are associated with elevated mortality risk and health care costs across all levels of frailty.