The cumulative effect of frailty and cognition on mortality – results of a prospective cohort study

BACKGROUND: Both physical frailty and cognitive impairment predict death, but the joint effect of these two factors is uncertain. The objectives are to determine if the Mini-mental state examination (MMSE) and the Frailty Index (FI) predict death over a five-year interval after accounting for the effect of the other; and if there is an interaction in this effect. METHODS: An analysis of an existing prospective cohort study of 1,751 community living older adults followed over a five-year time frame. Age, gender, and education were self-reported. The predictor variables were the FI - a measure of frailty based on the "Accumulation of Deficits" model of frailty; and the MMSE. Cox proportional hazards models were constructed for the outcome of time to death. RESULTS: The unadjusted Hazard Ratio (HR) (95% CI) for mortality was 2.17 (1.69, 2.80) for those who were only cognitively impaired, 2.02 (1.53, 2.68) for those who were only frail, and 3.57 (2.75, 4.62) for those who were both frail and cognitively impaired with the reference group of those who were neither frail nor cognitively impaired. Adjusted for age, gender, and education, the HR (95% CI) was 1.49 (1.13. 1.95) for those who were only cognitively impaired, 1.81 (1.35, 2.41) for those who were only frail, and 2.28 (1.69, 3.09) for those who were both frail and cognitively impaired. CONCLUSIONS: Both frailty and cognitive impairment are predictors of mortality and the effect is cumulative. There was no interaction in this effect.