Background: The aim of the study was to investigate whether urinary tract infection (UTI) in a representative sample of 85-, 90- and ≥95-year-old women is associated with delirium.

Methods: In 504 out of 643 women (78.4%) it was possible to evaluate UTI and delirium. Assessments such as the Organic Brain Syndrome (OBS) Scale, the Geriatric Depression Scale-15 (GDS-15) and the Mini-mental State Examination (MMSE) were performed during home visits. Delirium, dementia and depression were diagnosed according to the DSM-IV criteria. A diagnosed, symptomatic UTI with or without ongoing treatment, documented in medical records or detected in association with the assessments, was registered.

Results: Eighty-seven of 504 women (17.2%), were diagnosed as having a UTI with or without ongoing treatment when they were assessed, and almost half of them (44.8%) were diagnosed to be delirious or having had episodes of delirium during the past month. One hundred and thirty-seven of the 504 women (27.2%) were delirious or had had episodes of delirium during the past month and 39 (28.5%) of them were diagnosed to have a UTI. In a multivariate logistic regression model, delirium was significantly associated with Alzheimer's disease (OR = 5.8), multi-infarct dementia (OR = 5.4), depression (OR = 3.1), heart failure (OR = 2.3) and urinary tract infection (OR = 1.9).

Conclusions: A large proportion of very old women with UTI suffered from delirium which might indicate that UTI is a common cause of delirium. There should be more focus on detecting, preventing and treating UTI to avoid unnecessary suffering among old women.