Preexisting Atrial Fibrillation Linked to Higher Delirium Risk in Critical Illness: Study
USA: Researchers have found in a new study that preexisting atrial fibrillation (AF) was independently associated with an increased risk of delirium during critical illness. This suggests that AF may contribute to cerebrovascular vulnerability beyond underlying comorbidities. The findings support consideration of targeted delirium-prevention strategies for critically ill patients with AF.
Delirium is a common form of acute brain dysfunction among critically ill patients and can be associated with prolonged hospitalization and adverse outcomes. AF has previously been linked to chronic cognitive impairment and dementia, with proposed mechanisms including impaired cerebral perfusion, inflammation, vascular dysfunction, and thromboembolic or bleeding-related brain injury. However, whether AF is associated with delirium during critical illness has remained uncertain.
To investigate this relationship, Austin Milton, MD, Department of Internal Medicine, Spencer Fox Eccles School of Medicine, University of Utah, Salt Lake City, UT, and colleagues conducted a retrospective cohort study at a tertiary academic medical center. The analysis, published in Heart Rhythm O2 included adult patients admitted to the intensive care unit (ICU) between October 2015 and January 2026.
The primary outcome was delirium burden, measured as the proportion of ICU days during which patients had a positive Confusion Assessment Method for the ICU (CAM-ICU) assessment. Researchers used linear regression models to examine the association between preexisting AF and delirium while accounting for vascular comorbidities using CHA2DS2-VASc scores and other baseline characteristics.
The study included 50,667 unique patients, of whom 18.0% had preexisting AF. Patients with AF were generally older and had a greater burden of comorbidities than those without the arrhythmia.
Key findings:
- Patients with preexisting AF had a greater burden of delirium during critical illness.
- The proportion of ICU days affected by delirium was higher among patients with AF than those without AF (0.20 versus 0.15).
- AF was associated with longer periods of delirium, higher APACHE II scores, and increased mortality in unadjusted analyses.
- After adjustment for CHA2DS2-VASc and other baseline characteristics, AF remained independently associated with an absolute 3.37% increase in delirium burden.
The study had several limitations, including its retrospective, single-center design, which limits causal inference and generalizability. Residual confounding may persist despite adjustment, particularly given the older age and greater comorbidity burden among patients with AF. Electronic health records may have missed paroxysmal AF, while routine CAM-ICU assessments could have introduced measurement variability.
The researchers concluded that preexisting AF was significantly associated with increased delirium during critical illness, suggesting that the relationship may extend beyond the vascular risk factors shared by AF and cognitive dysfunction. Hemodynamic and cerebrovascular mechanisms may contribute to this vulnerability. The findings also highlight the need for future studies examining whether strategies targeting AF prevention or management in critically ill patients can reduce delirium risk.
Reference:
Milton, A., Tonna, J. E., Zhang, C., Presson, A. P., Holbrook, R., Martinez-Parachini, J., Konstantinidis, K., Freedman, R., Engels, M. C., Lehmann, I., Ranjan, R., & Bunch, T. J. (2026). Preexisting Atrial Fibrillation is Associated with Increased Risk of Delirium During Critical Illness: An Analysis of Incidence, Timing, and Risk Factors. Heart Rhythm O2. https://doi.org/10.1016/j.hroo.2026.09.005
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