Pre‐Fracture Cognitive Assessment Using the DASC‐21 and Postoperative Delirium Risk
ABSTRACT Background Postoperative delirium (POD) is a common complication in older adults after hip fracture surgery. Although cognitive impairment is a key risk factor, accurately assessing baseline cognition in acute settings remains challenging. Informant‐based tools may better reflect premorbid cognitive status; however, their utility in hip fracture populations is unclear. Methods This retrospective analysis used data from a prospective cohort of patients aged ≥ 80 years who underwent hip fracture surgery at two acute hospitals in Japan. Pre‐fracture cognitive status was assessed using the Dementia Assessment Sheet for Community‐based Integrated Care System (DASC‐21), primarily based on reports from informants. For selected patients without available informants and with Mini‐Mental State Examination (MMSE) scores ≥ 21, structured patient interviews and clinical observations were used. The DASC‐21 categories were classified as normal cognition, mild impairment and moderate‐to‐severe impairment. Cognitive function at admission was evaluated using the MMSE. POD was assessed using the Confusion Assessment Method within the first three postoperative days. Multivariable logistic regression analyses were performed. Results Among 368 patients, 137 (37.2%) developed POD. POD incidence increased with worsening pre‐fracture cognitive impairment (5.6%, 44.3% and 48.7% for normal, mild and moderate‐to‐severe impairment, respectively; p < 0.001). Each 1‐point increase in the MMSE score was associated with lower odds of POD (OR 0.91, 95% CI 0.88–0.94). Compared with normal cognition, the adjusted ORs for POD were 14.11 (95% CI 5.08–39.24) for mild impairment and 15.39 (95% CI 5.56–42.61) for moderate‐to‐severe impairment. Discrimination was similar between MMSE and DASC‐21 (area under the receiver operating characteristic curve 0.75 vs. 0.74). Conclusions Pre‐fracture cognitive impairment, including DASC‐21‐defined mild impairment, was associated with POD. The DASC‐21 categories showed comparable discriminative performance to the MMSE and may help estimate baseline cognitive vulnerability in acute clinical settings.