Delirium Occurrence in Older Irish Adults Admitted to an Acute Medical Hospital: a Prospective Cohort Study

Objectives: Delirium, which is associated with adverse health outcomes, is poorly detected in hospital settings. This study aimed to determine delirium occurrence among older medical inpatients and to capture associated risk factors.

Methods: This prospective cohort study was performed at an Irish University Hospital. Medical inpatients 70 years and over were included. Baseline assessments within 72 hours of admission included delirium status and severity as determined by the Revised Delirium Rating Scale (DRS-R-98), cognition, physical illness severity and physical functioning. Pre-existing cognitive impairment was determined with Short Informant Questionnaire on Cognitive Decline (IQCODE). Serial assessment of delirium status, cognition and the physical illness severity were undertaken every 3 (±1) days during participants' hospital admission.

Results: Of 198 study participants, 92 (46.5%) were women and mean age was 80.6 years (s.d. 6.81; range 70-97). Using DRS-R-98, 17.7% ( = 35) had delirium on admission and 11.6% ( = 23) had new-onset delirium during admission. In regression analysis, older age, impaired cognition and lower functional ability at admission were associated with a significant likelihood of delirium.

Conclusions: In this study, almost one-third of older medical inpatients in an acute hospital had delirium during admission. Findings that increasing age, impaired cognition and lower functional ability at admission were associated with increased delirium risk suggest target groups for enhanced delirium detection and prevention strategies. This may improve clinical outcomes.