Joint Trajectories of Frailty and Cognitive Function in Older Koreans Based on 14‐Year Period Data From Korean Longitudinal Study of Aging ( KLoSA )

AIM: Frailty and cognitive impairment are age-related, interrelated conditions that significantly affect older adults' quality of life and independence. Although they often co-occur, studies examining their trajectories simultaneously are limited. This study aimed to identify multiple joint trajectories of frailty and cognitive functioning and examine how sociodemographic and lifestyle factors relate to these trajectories. METHODS: Using data from 2766 respondents aged 65 years or older in the Korean Longitudinal Study of Aging (2006-2020), with an average of 6.4 repeated measurements per participant, group-based trajectory modeling was applied. Multinomial regression was conducted to assess associations of frailty and cognitive impairment with sociodemographic and lifestyle factors. RESULTS: Three joint trajectories were identified: robust (53.7%), cognitive decline with progressive frailty (33.0%), and rapid and simultaneous worsening (13.2%). Older age, being single, lower education, unemployment, smoking, and physical inactivity were linked to a higher likelihood of rapid and simultaneous worsening of frailty and cognitive function. CONCLUSIONS: Findings reveal substantial heterogeneity in aging as manifested by joint trajectories of frailty and cognitive function. Interventions should prioritize the identification of a subgroup with early concurrent deterioration and target lifestyle factors among socially and economically vulnerable older adults.