Dynamics of Frailty and Cognition after Age 50: Why It Matters that Cognitive Decline is Mostly Seen in Old Age

Background: Frailty has been considered an antecedent and, to a lesser extent, an outcome of cognitive impairment. Both frailty and cognitive impairment are multiply determined and each is strongly related to age, making it likely that the two interact, especially as people age. In consequence, understanding their interaction and co-occurrence can offer insight into pathophysiology, prevention, and management. Objective: To examine the nature of the relationship between frailty and cognitive impairment using longitudinal data from the Survey of Health Aging and Retirement in Europe (SHARE), assessing for bidirectionality. Methods: We conducted secondary analyses using data from the first two waves of SHARE. The sample (N = 11,941) was randomly split into two halves: one half for model development and one half for model confirmation. We used a 65 deficit Frailty Index and combined 5 cognitive deficits into a global cognitive impairment index. Cross-lagged path analysis within a structural equation modelling framework was used to examine the bi-directional relationship between the two measures. Results: After controlling for age, sex, social vulnerability, education, and initial cognitive impairment, each 0.10 increase in baseline frailty was associated with a 0.01 increase in cognitive impairment at follow-up (p < 0.001). Likewise, each 0.1 increase in baseline cognitive impairment was associated with a 0.003 increase frailty at follow-up (p < 0.01). Conclusion: Our findings underscore the importance of considering cognitive impairment in the context of overall health. Many people with dementia are likely to have other health problems, which need to be considered in concert to achieve optimal health outcomes.