Biological sex and its influence on delirium in adult ICU patients: a single-centre retrospective cohort study

Background Delirium is common among ICU patients and has been shown to be consistently associated with worse outcomes. Distinct outcomes among biological sexes in ICUs are being increasingly recognised; however, their role in the risk of delirium remains poorly characterised. Methods This retrospective cohort study included adult patients admitted to ICUs at a tertiary-level academic medical centre from 2011 to 2024. The primary outcome was the incidence of delirium, measured using the Confusion Assessment Method for the ICU assessment tool as part of routine clinical care. Multivariable logistic regression analyses were used to characterise the association between biological sex and ICU delirium. Incidence of delirium between differing age groups and ICU admission types was also evaluated. Results Of the 38 192 patients included, 56.1% (21 541) were male. In total, 46% (17 447) of patients experienced delirium during their ICU stay. Compared with female patients, male patients had a lower incidence of ICU delirium (adjusted odds ratio [aOR], 0.88; 95% confidence interval [CI], 0.83–0.93; P <0.001). Stratified by admission type, male patients, both <60 yr and 60 yr and above, admitted to medical ICUs had a lower risk of developing delirium compared with female patients (aOR, 0.82; 95% CI, 0.72–0.93; P =0.002; aOR, 0.89; 95% CI, 0.83–0.97; P =0.008, respectively), whereas this association was not significant among patients admitted to surgical ICUs, regardless of age group. Conclusions Male patients had a lower incidence of ICU delirium. This association was most notable among patients admitted to medical ICUs. Assessment for delirium risk may include consideration of biological sex.