Background The use of anticholinergic medications in older adults has previously been associated with increased risk of dementia. However, it is unclear whether anticholinergic use is associated with delirium, and any potential link is confounded by frailty and the drug indications. Greater understanding of the risk of delirium with anticholinergic use is important in the medical management of older adults. We examined the association of anticholinergic use and admission to hospital with delirium in patients treated for overactive bladder (OAB).

Methods We performed a nested case-control study, from a population of 242,364 patients aged over 50 years prescribed an OAB drug (e.g. oxybutynin, solifenacin, tolterodine, mirabegron) during 2010–19 from general practices in England contributing to Clinical Practice Research Datalink Aurum with linkage to hospital admissions data. Cases were patients with a first emergency admission after their first OAB prescription between 2010–2019, and with delirium noted on the day or day after admission and prior to any surgery. We excluded patients with dementia or severe mental illness recorded before or during the hospital admission or <12 months registration at their general practice. Up to three patients with hospital admissions after first OAB prescription without delirium noted were matched to each case on primary admission reason, sex, age (+/- 10 years), and date (+/- 6 months). We used conditional logistic regression to estimate odds ratios (OR) for prescription of any overactive bladder anticholinergic (e.g. oxybutynin, solifenacin, tolterodine) in the past 90 days and delirium, adjusted for socio-demographics, comorbidities and concurrent prescriptions. We also estimated ORs for specific anticholinergic drugs compared to no prescription.

Results We included 7,944 patients admitted with delirium matched to 23,348 admissions without delirium recorded. The mean (SD) age of patients with delirium was 82 (9) years and 43% were men. The most common reasons for admission were urinary tract infection, pneumonia and other infections. A total of 3,447 (43%) cases and 8,977 (38%) controls were prescribed OAB medications in the past 90 days. The adjusted OR (95% CI) for any OAB anticholinergic and delirium was 1.22 (1.16–1.29). This increased likelihood of delirium was similarly noted across specific anticholinergic bladder medications such as solifenacin, tolterodine, and oxybutynin.

Conclusion Our study demonstrates an association between prescription of anticholinergic drugs for OAB and hospital admission with delirium. Similar associations were observed across each anticholinergic drug. Alternative management options for OAB in older patients should be considered before prescribing anticholinergic medications.