Predicting Mortality and Adverse Outcomes: Comparing the Frailty Index to General Prognostic Indices

Abstract

Background: Mortality prediction models are useful to guide clinical decision-making based on prognosis. The frailty index, which allows prognostication and personalized care planning, has not been directly compared with validated prognostic models. Objective: To compare the discrimination of mortality, disability, falls, and hospitalization between a frailty index and validated prognostic indices. Design: Secondary Analysis of the National Health and Aging Trends Study. Participants: Seven thousand thirty-three Medicare beneficiaries 65 years or older. Measurements: We measured a deficit-accumulation frailty index, Schonberg index, and Lee index at the 2011 baseline assessment. Primary outcome was mortality at 5 years. Secondary outcomes were decline in activities of daily living (ADL), decline in instrumental activities of daily living (IADL), fall, and hospitalization at 1 year. We used C-statistics to compare discrimination between indices, adjusting for age and sex. Results: The study population included 4146 (44.8%) with age ≥ 75 years, with a median frailty index of 0.15 (interquartile range 0.09–0.25). A total of 1385 participants died (14.7%) and 2386 (35.2%) were lost to follow-up. Frailty, Schonberg, and Lee indices predicted mortality similarly: C-statistics (95% confidence interval) were 0.78 (0.77–0.80) for frailty index; 0.79 (0.78–0.81) for Schonberg index; and 0.78 (0.77–0.80) for Lee index. The frailty index had higher C-statistics for decline in ADL function (frailty index, 0.80 [0.78–0.83]; Schonberg, 0.74 [0.72–0.76]; Lee, 0.74 [0.71–0.77]) and falls (frailty index, 0.66 [0.65–0.68]; Schonberg, 0.61 [0.58–0.63]; Lee, 0.61 [0.59–0.63]). C-statistics were similar for decline in IADL function (frailty index, 0.61 [0.59–0.63]; Schonberg, 0.60 [0.59–0.62]; Lee, 0.60 [0.58–0.62]) and hospitalizations (frailty index, 0.68 [0.66–0.70]; Schonberg, 0.68 [0.66–0.69]; Lee, 0.65 [0.63–0.67]). Conclusions: A deficit-accumulation frailty index performs as well as prognostic indices for mortality prediction, and better predicts ADL disability and falls in community-dwelling older adults. Frailty assessment offers a unifying approach to risk stratification for key health outcomes relevant to older adults.