Association between prescribing of anticholinergic medications and incident delirium: a cohort study

To describe the association between anticholinergic medications and incident delirium in hospitalized older adults with cognitive impairment and to test the hypothesis that anticholinergic medications would increase the risk of incident delirium.

Observational cohort study.

Urban public hospital in Indianapolis, Indiana.

One hundred forty-seven participants aged 65 and older with cognitive impairment who screened negative for delirium at the time of admission to a general medical ward.

Cognitive function at the time of admission was assessed using the Short Portable Mental Status Questionnaire (SPMSQ). Anticholinergic medication orders between the time of admission and the final delirium assessment were evaluated. Anticholinergic medication orders were identified using the Anticholinergic Cognitive Burden Scale. Delirium was assessed using the Confusion Assessment Method.

Fifty-seven percent of the cohort received at least one order for possible anticholinergic medications, and 28% received at least one order for definite anticholinergic medications. The incident rate for delirium was 22% of the entire cohort. After adjusting for age, sex, race, baseline SPMSQ score, and Charlson Comorbidity Index, the odds ratio (OR) for developing delirium in those with orders for possible anticholinergic medications was 0.33 (95% confidence interval (CI) = 0.10-1.03). The OR for developing delirium among those with orders for definite anticholinergic medications was 0.43 (95% CI = 0.11-1.63).

The results did not support the hypothesis that prescription of anticholinergic medications increases the risk of incident delirium in hospitalized older adults with cognitive impairment. This relationship needs to be established using prospective study designs with medication dispensing data to improve the performance of predictive models of delirium.