Hospital delirium associated with subsequent psychiatric disorders in older adults

A matched cohort study published in BMC Medicine examined whether in-hospital delirium was associated with subsequent psychiatric disorders using UK Biobank inpatient records from England, Scotland, and Wales (1997–2022). Researchers matched 14,909 adults with a first recorded delirium episode to 14,909 controls on demographic and hospital characteristics, including frailty. Mean age was 72.1 years, 57% were men, and follow-up extended to 26 years. Outcomes were new inpatient-coded psychotic, bipolar, depressive, and anxiety disorders.

Psychiatric disorder incidence was 6.7 per 100 person-years among participants with delirium versus 4.9 without delirium. The adjusted subdistribution hazard ratio (SHR), accounting for competing mortality, was 1.44 (95% CI 1.31–1.59). Associations were strongest for psychotic disorders (SHR 3.79, 95% CI 2.63–5.45) and bipolar disorders (3.44, 1.90–6.20), followed by depression (1.52, 1.36–1.70) and anxiety (1.37, 1.22–1.54). Personality disorders, the negative-control outcome, showed no association.

Only psychotic disorders showed a dose-response association with recurrent delirium: each additional episode within 12 months was associated with a 23% higher subdistribution hazard (SHR 1.23, 95% CI 1.09–1.39). These findings identify delirium as a marker of subsequent psychiatric morbidity. However, the observational design cannot establish that delirium causes these disorders, and inpatient coding may miss diagnoses managed outside hospital. Whether delirium prevention reduces later psychiatric illness remains unproven.