Prevalence and Risk Factors for Delirium on Arrival at the Emergency Room by Ambulance

Delirium is an acute and often fluctuating disturbance in attention and awareness and is one of the organ dysfunctions caused by acute illness. A previous study revealed that 8.3% of older patients in the emergency room (ER) had delirium, and dementia and older age were identified as independent risk factors for delirium in the ER. However, different ER structures (intermediate or acute care units) and disease clusters may have different prevalence rates and risk factors.

This study aimed to identify the prevalence and risk factors for delirium on arrival at the ER.

This was an exploratory clinical trial and retrospective cohort study conducted at a tertiary care emergency center in Japan, including patients aged ≥20 years who were transported to and hospitalized at the ER between April 1, 2023, and March 31, 2024. Delirium was evaluated using the Brief Confusion Assessment Method. Multivariate analysis was performed on the 12 variables that were significantly different in the comparison of patient characteristics upon arrival at the ER.

Of the 20,660 patients who visited the ER, 1,486 patients who were transported by ambulance were included in this study. The prevalence of delirium upon arrival at the ER was 20.3% (301/1486 patients, 95% confidence intervals: 18.2-22.4). Multivariable logistic regression analysis revealed a significant association between delirium on arrival at the ER and older age (odds ratio (OR) 1.02, 95% confidence interval (CI) 1.01-1.04), past history of dementia (OR 3.94, 95%CI 2.41-6.44) and psychiatric illness (OR 2.76, 95%CI 1.41-5.40), higher Glasgow Coma Scale (GCS) scores (OR 0.34, 95%CI 0.29-0.40), and requiring oxygen therapy on arrival at the ER (OR 2.09, 95%CI 1.45-3.02).

The prevalence of delirium on arrival at the ER was approximately 20%. Our findings suggest that older age, history of dementia and psychiatric illness, low GCS score at presentation, and the need for oxygen therapy may be risk factors for delirium symptoms at presentation.