Co‐development of frailty and functional ability in older adults: A parallel‐process latent growth curve model

AIM: To explore the co-development and possible risk factors of frailty and functional ability among community-dwelling older adults. METHODS: This secondary analysis used data from a prospective three-wave cohort study with a sample of 780 older adults. Frailty was assessed using the Tilburg Frailty Indicator, and functional ability using the Lawton Instrumental Activities of Daily Living Scale. A conditional parallel-process latent growth curve model was implemented to test their dynamic relationship and explore the potential risk factors. RESULTS: Frailty and functional ability significantly deteriorated over 3 years. Older adults with severer frailty were more likely to experience poor initial functional ability as well as a faster loss of functional ability, and a rapid functional ability decline was more easily observed in participants suffering an accelerating increase in frailty deterioration. Furthermore, lack of a spouse and the presence of comorbidities were significantly related to severer initial frailty, while lower educational attainment was associated with poorer baseline functional ability. Advanced age impaired initial functional ability and accelerated its rate of deterioration over time. CONCLUSIONS: Frailty and functional ability significantly deteriorated over a 3-year period, and the frailty trajectory significantly affected the evolution of functional ability. In addition, age, marital status, educational level, and multimorbidity were significant risk factors. These results underscore the importance of timely and tailored approaches addressing frailty and risk factors for maintaining functional ability and promoting healthy aging among community-dwelling older populations. Geriatr Gerontol Int 2025; 25: 1223-1230.