Delirium and Long-Term Cognitive Trajectories in Cognitively Unimpaired Adults

Importance: Delirium is a state of acute confusion characterized by deficits in attention that occurs commonly during hospitalization and is associated with adverse outcomes; however, the association of delirium with longitudinal cognitive trajectories is not fully understood. Objective: To evaluate the association of delirium during hospitalization with subsequent development of mild cognitive impairment (MCI), dementia, and longitudinal cognitive trajectories. Design, Setting, and Participants: This cohort study used data from participants with hospitalizations in the Mayo Clinic Study of Aging (MCSA) from October 2004 to December 2023. The MCSA is a prospective, population-based longitudinal study of cognitive aging among residents of Olmsted County, Minnesota. Of participants enrolled in the MCSA between 2004 and 2023, individuals who experienced 1 or more hospitalization prior to their last MCSA encounter were included in this study. Participants with dementia at MCSA enrollment or prior to first hospitalization were excluded. Follow-up continued until development of MCI or dementia, last MCSA visit, or the end of the study. Exposure: Delirium was identified using a validated natural language processing algorithm applied to clinical notes from hospitalizations, associated emergency department visits, and follow-up within 30 days after hospitalization. Delirium status was modeled as a time-dependent exposure. Main Outcomes and Measures: Incident MCI and dementia were assigned through MCSA expert consensus evaluations, including neuropsychological testing performed every 15 months. Association between delirium and development of MCI or dementia was assessed using Cox proportional hazards regression, adjusted for patient age, sex, level of education, and apolipoprotein E (APOE) ε4 allele carrier status; cognitive trajectories were assessed with linear mixed-effects models. Results: Of 7030 participants enrolled in the MCSA, 3542 individuals experienced 1 or more hospitalization prior to their last MCSA encounter and were included, and 41 participants with dementia at enrollment or prior to first hospitalization were excluded. The cohort included 3501 participants with at least 1 hospitalization. Median (IQR) age was 74.1 (66.6-80.9) years, 1676 participants (47.9%) were female, median (IQR) level of education was 14 (12-16) years, and 910 participants (26.0%) were APOE ε4 carriers. During a median (IQR) follow-up of 7.2 (4.1-10.4) years, 75 participants (2.1%) had delirium documented within 30 days of hospitalization. Delirium was associated with increased risk of MCI (adjusted hazard ratio [aHR], 3.67; 95% CI, 2.19-6.15) and dementia (aHR, 5.39; 95% CI, 2.94-9.85) and with accelerated decline in longitudinal cognitive testing. Conclusions and Relevance: In this cohort study among adults in the MCSA, including those with unimpaired cognition at baseline, delirium during hospitalization was strongly associated with increased risk of MCI and dementia and accelerated cognitive decline in subsequent years.