Frailty Index and incident mortality, hospitalization and institutionalization in Alzheimer’s disease: data from the ICTUS study

BACKGROUND: The identification of an objective evaluation of frailty capable of predicting adverse outcomes in Alzheimer’s disease (AD) is increasingly discussed. The purpose of this study was to investigate whether the Frailty Index (FI) predicts hospitalization, institutionalization and mortality in AD patients. METHODS: Prospective multicenter cohort study (follow-up=2 years), including 1,191 subjects with AD. The outcomes of interest were incident hospitalization, institutionalization, and mortality. The FI was calculated as the ratio of actual to thirty potential deficits, i.e. deficits presented by the participant divided by 30. Severity of dementia was assessed using the Clinical Dementia Rating (CDR) score. Cox proportional hazard models were performed. RESULTS: Mean age of the study sample was 76.2 (standard deviation=7.6) years old. A quadratic relationship of the FI with age was reported at baseline (R2=0.045, p<0.001). The FI showed a statistically significant association with mortality (age- and gender-adjusted HR=1.019, 95%CI=1.002-1.037, p=0.031) and hospitalization (age- and gender-adjusted HR=1.017, 95%CI=1.006-1.029, p=0.004), and a borderline significance with institutionalization. When the CDR score was simultaneously included in the age- and gender-adjusted models, the FI confirmed its predictive capacity for hospitalization (HR=1.019, 95%CI=1.006-1.032, p=0.004), whereas the CDR score was the strongest predictor for mortality (HR=1.922, 95%CI=1.256-2.941, p=0.003) and institutionalization (HR=1.955, 95%CI=1.427-2.679, p<0.001). CONCLUSIONS: The FI is a robust predictor of adverse outcomes even after the stage of the underlying dementia is considered. Future work should evaluate the clinical implementation of the FI in the assessment of demented individuals in order to improve the personalization of care.