Association of transitions in frailty with dementia risk: findings from two longitudinal cohort studies

Introduction Previous studies have suggested that frailty is an important risk factor for dementia. Frailty is a dynamic condition that may progress or improve. However, the impact of frailty transitions on dementia risk has not been sufficiently examined. Methods We analyzed data from two prospective cohorts. Frailty status was assessed using the Frailty Index (FI) and categorized into three groups: robust, pre-frail, and frail. Transitions in frailty status were evaluated based on FI at baseline and at a second assessment. The outcome was dementia, which was ascertained by self-reported physician diagnosis. To adjust for potential confounders, a directed acyclic graph was drawn, and Cox proportional hazards models were used to calculate hazard ratio (HR) and 95% confidence interval (95% CI). Results Based on the inclusion and exclusion criteria, a total of 8,353 participants were included in the analysis of transitions in frailty status. Compared with stable robust participants, robust participants who progressed to pre-frail or frail had an increased risk of dementia (HR = 1.78, 95% CI: 1.18–2.68, p = 0.006). Compared with stable pre-frail participants, pre-frail participants who progressed to frail also had a significantly higher risk of dementia (HR = 1.97, 95% CI: 1.39–2.81, p 0.001). However, the difference in dementia risk between pre-frail participants who reverted to robust status and stable pre-frail was not statistically significant (HR = 1.24, 95% CI: 0.80–1.92, p = 0.342). Similarly, the difference in dementia risk between frail participants who improved to pre-frail or robust status and stable frail was not statistically significant (HR = 0.94, 95% CI: 0.62–1.41, p = 0.754). The results of the sensitivity analyses were generally consistent with those of the main analysis, supporting the robustness of the findings. Conclusion Progression in frailty status was associated with an increased risk of dementia compared with stable robust or stable pre-frail status, whereas recovery from pre-frail or frail status was not associated with a significant reduction in dementia risk.