Causes and prognosis of delirium in elderly patients admitted to a district general hospital

Background: delirium is common and is associated with a high early mortality, but less is known about the longer term prognosis. Design: case-controlled prospective study. Methods: all relevant wards were contacted weekly by a research nurse and the nurses were asked to report all patients presenting with confusion. Patients satisfying the American Psychiatric Association's Diagnostic and Statistical Manual III criteria were included. The diagnosis of delirium was confirmed by a consultant physician. Delirious patients were then followed-up throughout their hospital admission to ascertain the cause of their delirium, and assessed for visual and hearing impairment. The patients were assessed again at 6 and 12 months. Control patients, who were in hospital at the same time and on similar wards, but were not confused, were also examined and followed-up. Results: 171 patients with delirium were identified (78 men and 93 women, mean age 81 years). The commonest cause of delirium was infection (34% of cases), but in 25% there were multiple equally contributory causes. Vision and hearing impairment was significantly more common in patients with delirium [odds ratio (OR) 12.62; confidence intervals (CI) 2.86-114.04, P < 0.001). After 1 year, patients presenting with delirium had an increased mortality (OR 2.30; 95% CI 1.25-4.35, P = 0.006), an increased institutionalization rate (OR 4.53; 95% CI 1.80-13.56, P = 0.001) and an increased likelihood of having been re-admitted (OR 2.05; 95% CI 1.19-3.54, P = 0.008). Conclusion: delirium has a poor long-term prognosis and may be a marker for functional deterioration and decline in elderly people.