Assistant Professor University of Hong Kong, Hong Kong
Background: Despite several studies showing the association between anticholinergic medications and increased risk of delirium, the change in delirium risk before and after anticholinergic treatment has not been explored in people with dementia.
Objectives: To investigate the association between anticholinergic burden and risk of incident delirium in people with dementia.
Methods: In this self-controlled case series (SCCS), we identified people with dementia, prescribed anticholinergic medications and who had incident delirium (outcome) between 2004 and 2019 using electronic healthcare records in Hong Kong. All anticholinergic medications (except antipsychotics and anxiolytics) were quantified by 1) summative Anticholinergic Cognitive Burden (ACB) Score 1, 2, and ≥ 3; and 2) the number of anticholinergic medications classes used in combination. The exposure windows were varied scores and combinations of medications and a 7-day pretreatment period. Conditional logistic regression models adjusting age and seasonality were used to compare the IRR between varied exposure periods and non-treatment periods. A non-parametric spline-based SCCS was built to measure continuous changes in risk.
Results: We identified 1687 patients with new delirium. Compared to the non-treatment period, the risks of incident delirium were high during the ACB scores of ≥ 3 (1.97, 1.62-2.39), ACB score of 2 (1.89, 1.50-2.38) and ACB score of 1 (1.50, 1.27, 1.79). However, the risks of delirium were even higher on day 0 (18.55, 13.21-26.05) and pre-treatment period (6.15, 4.89-7.74). Results were similar for the exposure of ACB combinations. A non-parametric SCCS also showed an increased risk before ACB treatment and remains elevated 30 days after the initiation.
Conclusions: The risk of incident delirium increased prior to initiation of ACB. The risk remains elevated and regressed to baseline after 30 days of exposure. Anticholinergic medications were likely not an important contributor to the risk of incident delirium in people with dementia. Multidisciplinary strategies for preventing delirium should consider both the anticholinergic burden and managing comorbidities in these groups of people.
