A Mediation Analysis Examining High Risk, Anticholinergic Medication Use, Delirium, and Dementia After Major Surgery.

INTRODUCTION: Anticholinergic medications are known to cause adverse cognitive effects in community-dwelling older adults and medical inpatients, including dementia. The prevalence with which such medications are prescribed in older adults undergoing major surgery is not well described nor is their mediating relationship with delirium and dementia. We sought to determine the prevalence of high-risk medication use in major surgery patients and their relationship with the subsequent development of dementia.

METHODS: This was a retrospective cohort study which used data between January 2013 and December 2019, in a large midwestern health system, including sixteen hospitals. All patients over age 50 undergoing surgery requiring an inpatient stay were included. The primary exposure was the number of doses of anticholinergic medications delivered during the hospital stay. The primary outcome was a new diagnosis of Alzheimer's disease and related dementias at 1-y postsurgery. Regression methods and a mediation analysis were used to explore relationships between anticholinergic medication usage, delirium, and dementia.

RESULTS: There were 39,665 patients included, with a median age of 66. Most patients were exposed to anticholinergic medications (35,957/39,665; 91%), and 7588/39,665 (19.1%) patients received six or more doses during their hospital stay. Patients with at least six doses of these medications were more likely to be female, black, and with a lower American Society of Anesthesiologists class. Upon adjusted analysis, high doses of anticholinergic medications were associated with increased odds of dementia at 1 y relative to those with no exposure (odds ratio 2.7; 95% confidence interval 2.2-3.3). On mediation analysis, postoperative delirium mediated the effect of anticholinergic medications on dementia, explaining an estimated 57.6% of their association.

CONCLUSIONS: High doses of anticholinergic medications are common in major surgery patients and, in part via a mediating relationship with postoperative delirium, are associated with the development of dementia 1 y following surgery. Strategies to decrease the use of these medications and encourage the use of alternatives may improve long-term cognitive recovery.