Delirium is a frequent occurrence in the intensive care unit (ICU). It is associated with increased hospital costs (Gou et al., 2021), hospital stay duration, mortality and morbidity during hospitalisation (Maniar et al., 2016). Patients with delirium experience greater short-term cognitive impairment and long-term cognitive decline (Inouye et al., 2016). Regarding delirium incidence, it was reported to be nearly 32 % in a sample of patients undergoing aortic valve replacement (i.e., those with aortic stenosis undergoing surgical aortic valve replacement or transcatheter aortic valve replacement) (Maniar et al., 2016), and up to 71 % in a large multicentre group of older patients (Girard et al., 2018).

Following ICU discharge, patient memory influences quality of life (Barreto et al., 2019), and there are reports of unreal experiences and delusional memories in ICU survivors (Wang et al., 2020). Patients with delirium (vs. without delirium) reported decreased memory and neurobehavioral functioning at both six months and one year (Basinski et al., 2010), and had fewer factual and more delusional memories at one week, two months, and six months post-ICU discharge (Svenningsen et al., 2014). In critically-ill survivors, cognitive impairment affected memory, attention, processing speed, and emotional consequences (Nouwen et al., 2012, Rengel et al., 2019). Furthermore, the presence of delusional memories increased posttraumatic stress disorder (PTSD) risk after ICU admission (Askari Hosseini et al., 2021, de Pellegars et al., 2023).

PTSD is a mental disorder that can develop after ICU exposure, and has shown an incidence of approximately 25 % at 1–6 months and 17 % at 7–12 months post-ICU discharge (Jensen et al., 2015). PTSD is characterised by, for example, trauma-related intrusive memories and nightmares, poor concentration, and emotional withdrawal (Yehuda et al., 2015). ICU patients under mechanical ventilation in a study experienced extreme stress, which manifested as nightmares and fear, and was significantly and independently associated with PTSD (Garrouste-Orgeas et al., 2019, Sheaves et al., 2023). In another study, the ICU delirium–PTSD symptoms correlation was non-significant and weak, and the ICU memories–post-ICU PTSD correlation was also inconclusive (Svenningsen et al., 2015). Furthermore, delirium and long-term emotional outcomes are reported to not be associated, and the evidence on the delusional memories–adverse emotional outcomes correlation is contradictory (Nouwen et al., 2012). ICU-acquired delirium was shown to increase PTSD risk in ICU survivors (Bashar et al., 2018, Grover et al., 2019), albeit delirium experience and duration did not correlate with PTSD and related symptoms (Jackson et al., 2014, Slor et al., 2013, Wolters et al., 2016). Therefore, the current literature features inconsistent evidence on these topics.

This study primarily aimed to explore the differences in post-ICU memory, PTSD, and PTSD-related symptoms between patients with and without delirium. It also assessed whether delirium influences post-ICU memory and PTSD, and the correlations between post-ICU memory and PTSD symptoms in this sample.