Association of combined mobility and cognitive impairments with adverse health outcomes in adults aged 66 years: a nationwide cohort study

BACKGROUND: We examined whether cognitive frailty, defined as the coexistence of cognitive and mobility impairments, predicts the long-term risks of incident dementia and other adverse outcomes in a nationwide cohort of community-dwelling adults aged 66 years. METHODS: We analyzed 741,655 adults aged 66 years from the Korean National Health Insurance Service database (screening years, 2009-2012). Cognitive impairment was defined as a Korean Dementia Screening Questionnaire-Prescreening score of ≥4. Mobility impairment was defined as a Timed Up and Go (TUG) time of >10 seconds. The participants were classified into four groups: preserved mobility/cognitively normal (reference), preserved mobility/cognitive impairment, mobility impairment/cognitively normal, and mobility impairment/cognitive impairment (cognitive frailty). Cox models estimated hazard ratios (HRs) for all-cause mortality. Fine-Gray models estimated subdistribution HRs (SHRs) for dementia, disability, and long-term care service (LTCS) utilization, accounting for the competing risk of death. RESULTS: Over a mean follow-up of 10.9±2.6 years, 84,220 participants (11.4%) developed dementia. Compared with the reference group, cognitive frailty was associated with higher dementia incidence (adjusted SHR, 1.74; 95% confidence interval [CI], 1.67-1.81). Cognitive frailty was also associated with elevated risks of death (adjusted HR, 1.34; 95% CI, 1.29-1.40), disability (adjusted SHR, 1.42; 95% CI, 1.34-1.49), and LTCS utilization (adjusted SHR, 1.44; 95% CI, 1.38-1.49). CONCLUSION: Cognitive frailty defined by cognitive impairment and TUG-based mobility impairment, identified older adults with an increased long-term risk of dementia and other adverse health outcomes. This finding may serve as a practical screening marker during the transition to older age.