Trends and Predictors of Oral Anticoagulant Use in People with Alzheimer's Disease and the General Population in Australia

Background: People with Alzheimer's disease (AD) are less likely to use oral anticoagulants than people without AD. Objective: We investigated incidence and prevalence of warfarin and direct oral anticoagulant (DOAC) use, and determined predictors of DOAC and warfarin initiation in older people with AD and the general population. Methods: Australian Pharmaceutical Benefits Scheme data for 356,000 people aged ≥65 years dispensed warfarin or DOACs during July 2013-June 2017 were analyzed. Changes in annual incidence and prevalence were estimated using Poisson regression. Predictors of DOAC versus warfarin initiation were estimated using multivariable logistic regression separately for people with AD and the general population. Results: Oral anticoagulant prevalence increased from 8% in people with AD and 9% in the general population to 12% in both groups from 2013/2014 to 2016/2017. DOAC prevalence increased (from 2.4% to 7.8% in people with AD, 3.2% to 7.7% in the general population) while warfarin prevalence declined (6.6% to 4.5%, 7.0% to 4.3%, correspondingly). The incidence of warfarin use decreased by 45-55%. In people with AD, women were less likely to initiate DOACs than men, whereas presence of arrhythmias or pain/inflammation increased likelihood of initiating DOACs. Age ≥85 years, cardiovascular diseases, gastric acid disorder, diabetes, and end-stage renal disease were associated with lower odds of DOAC initiation in the general population. Conclusion: DOAC introduction has coincided with increased anticoagulation rates in people with AD. Rates are now similar in older people with AD and the general population. Compared to previous years, DOACs are now more likely to be initiated, particularly for those aged ≥85 years.