Delirium and subsequent psychiatric disorders in hospitalised older adults

Abstract Background Delirium is an acute confusional state and a frequent and potentially preventable complication of hospital admission. It is frequently accompanied by agitation and hallucinations reflecting physiological stress on the brain, and may precipitate psychiatric disorders in vulnerable individuals. We examined whether in-hospital delirium is associated with new-onset psychiatric disorders. Methods We conducted a matched cohort study using UK Biobank inpatient records from England, Scotland, and Wales (1997–2022), with follow-up up to 26 years. Adults with a first ICD-10 coded hospital episode of delirium (n = 14,909) were matched 1:1 to controls without recorded delirium on age, sex, Hospital Frailty Risk Score, primary diagnosis, length of stay, and ICU admission. Prespecified incident psychotic, bipolar, depressive, and anxiety disorders were identified from inpatient ICD‑10 codes. Personality disorders served as a negative-control. Associations were estimated as subdistribution hazard ratios (SHRs) from Fine–Gray models adjusted for competing risk of death, socioeconomic factors, and polygenic risk scores for schizophrenia and bipolar disorder. Results Among 29,818 participants (mean age 72.1 years; 57% men), incidence of any psychiatric disorder was 4.9 per 100 person-years in hospitalised participants without delirium and 6.7 per 100 person-years with delirium. Delirium was associated with a 44% higher incidence of any psychiatric disorder (SHR 1.44, 95% CI 1.31–1.59). Risk was greatest for psychotic disorders (3.79, 2.63–5.45) and bipolar disorders (3.44, 1.90–6.20), followed by depressive (1.52, 1.36–1.70) and anxiety (1.37, 1.22–1.54) disorders. No association was found for personality disorders. Only psychotic disorders showed a dose-response relationship with recurrent delirium: each additional delirium episode within 12 months conferred 23% higher risk (1.23, 1.09–1.39). Conclusions In-hospital delirium is associated with increased long-term incidence of psychiatric disorders, with psychotic disorders showing a particularly strong and dose-dependent association. Delirium might represent a potentially modifiable risk factor for subsequent mental illness that warrants further investigation.