The effects of frailty and cognitive impairment on 3-year mortality in older adults

Abstract

OBJECTIVES: Frailty and cognitive impairment in late life increase the risk of mortality. Physical frailty is closely associated with cognitive impairment. The aim of the study was to examine the independent and interaction effects of frailty and cognitive impairment in predicting mortality. STUDY DESIGN: A nationally representative sample of community-dwelling Koreans aged 65 years and older (n=11,266) was followed for 3 years. MAIN OUTCOME MEASURES: Frailty was categorized using Fried's phenotype model. Cognitive impairment was defined as more than 1.5 standard deviations below the age-, gender-, and education-specific norm of the Mini-Mental State Examination. Cox proportional hazards regression was used to analyze the mortality risk by frailty status and the moderating effect of cognitive impairment. RESULTS: Frailty was associated with cognitive impairment, with 922 (19.1%), 1609 (28.1%), and 392 (42.8%) of the nonfrail, prefrail, and frail group, respectively, being cognitively impaired. Compared with the nonfrail group, those who were prefrail (hazard ratio [HR]=1.38: 95% confidence interval [CI]: 1.10, 1.73) and frail (HR=1.78, 95% CI: 1.29, 2.46) had higher mortality rates, after adjusting for sociodemographic variables, health behaviors, and chronic conditions. Cognitive impairment was associated with a 30% increased mortality rate. A significant interaction between frailty and cognitive impairment was observed (p=0.003). Compared with those nonfrail and not cognitively impaired, frail persons with cognitive impairment had a lower survival rate (HR=1.92, 95% CI: 1.26, 2.93). CONCLUSIONS: Frailty was a significant predictor of 3-year mortality in community-dwelling older adults, with the association being moderated by baseline cognitive status. Taking cognitive function into account may allow better prediction of adverse outcomes of frailty in later life.