Association of Longitudinal Trajectories of Physical Frailty With Dementia Status in Older Adults: A National Cohort Study

Abstract

Background and Objectives: The longitudinal patterns of change in physical frailty and their associations with the subsequent dementia risk remain unclear. This study aimed to (1) explore the long-term trajectories of physical frailty over a 6-year period in older adults without dementia at baseline; (2) identify the socio-demographic and health-related factors associated with different physical frailty trajectories; and (3) examine the longitudinal relationships between different physical frailty trajectories and subsequent risk of dementia. Research Design and Methods: This national cohort study used data from the National Health and Aging Trends Study (NHATS) conducted in the United States from 2015 to 2021 and included adults aged ≥ 65 without dementia (n = 2245) at baseline in 2015. Group-based trajectory modeling was used to describe the longitudinal changes. Socio-demographic and health-related characteristics were compared across the identified physical frailty trajectories using bivariate analyses, employing Rao–Scott chi-square tests for categorical variables and design-based F-tests for continuous variables. Multinomial logistic regression analyses were conducted to examine the relationships between different frailty trajectories and subsequent dementia status. Results: Three frailty trajectories were identified: low-stable (74.00%), low-increasing (21.14%), and high-level (4.86%). Participants in the low-increasing and high-level groups were predominantly older, female, minorities, unmarried, and less educated and had a lower income, more comorbidities, and greater anxiety and depression symptoms (p < 0.001). Compared with the low-stable group, older adults in the low-increasing group had higher risk of possible dementia (RRR: 2.37, 95% CI: 1.41–3.97, p < 0.001) and probable dementia (RRR: 1.71, 95% CI: 1.08–2.73, p = 0.02); similarly, older adults in the high-level group had higher risks of possible dementia (RRR: 4.24, 95% CI: 1.74–10.36, p < 0.001) and probable dementia (RRR: 2.99, 95% CI: 1.32–6.76, p = 0.01). No significant differences were found in the risk of dementia between the high-level frailty group and the low-increasing frailty group (p > 0.05). Conclusion and Implications: This study highlighted the importance of regular frailty monitoring for early detection and informed future interventions that could delay frailty progression and potentially reduce dementia risk.