Anticholinergic Burden Does Not Influence Delirium Subtype or the Delirium–Mortality Association in Hospitalized Older Adults: Results from a Prospective Cohort Study

BACKGROUND: Anticholinergic burden (ACB) is associated with an increased risk of delirium in the older population outside of the acute hospital setting. In acute settings, delirium is associated with increased mortality, and this association is greater with full syndromal delirium (FSD) than with subsyndromal delirium (SSD). Little is known about the impact of ACB on delirium prevalence or subtype in hospitalized older adults or the impact on mortality in this population. OBJECTIVES: Our objectives were to determine whether ACB moderates associations between the subtype of delirium experienced by hospitalized older adults and to explore factors (including ACB) that might moderate consequent associations between delirium and mortality in hospital inpatients. METHODS: We conducted a retrospective analysis of a cohort of 784 older adults with unplanned admission to a North London acute medical unit between June and December 2007. Univariate regression analyses were performed to explore associations between ACB, as represented by the Anticholinergic Burden Scale (ACBS), delirium subtype (FSD vs. SSD), and mortality. RESULTS: The mean age of the sample was 83 ± standard deviation (SD) 7.4 years, and the majority of patients were female (59%), lived in their own homes (71%), were without dementia (75%), and died between hospital admission and the end of the 2-year follow-up period (59%). Mean length of admission was 13.2 ± 14.4 days. Prescription data revealed an ACBS score of 1 in 26% of the cohort, of 2 in 12%, and of ≥ 3 in 16%. The mean total ACBS score for the cohort was 1.1 ± 1.4 (range 0–9). Patients with high ACB on admission were more likely to have severe dementia, to have multiple comorbidities, and to live in residential care. Higher ACB was not associated with delirium of either subtype in hospitalized older adults. Delirium itself was associated with increased mortality, and greater associations were seen in FSD (hazard ratio [HR] 2.27; 95% confidence interval [CI] 1.70–3.01) than in SSD (HR 1.58; 95% CI 1.2–2.09); however, ACB had no impact on this relationship. CONCLUSIONS: ACB was not found to be associated with increased delirium of either subtype or to have a demonstrable impact on mortality in delirium. Prior suggestions of links between ACB and mortality in similar populations may be mediated by higher levels of functional dependence, greater levels of residential home residence, or an increased prevalence of dementia in this population.