Estimated Effects of Amyloid Reduction on Cognitive Change: A Bayesian Update across a Range of Priors

Abstract

Introduction: Results of the CLARITY-AD and GRADUATE I and II trials rekindled discussion on the impact of amyloid-targeting drugs. We use a Bayesian approach to quantify how a rational observer might update their prior beliefs based on new trial results. Methods: We used publicly available data from the CLARITY-AD and GRADUATE I & II trials to estimate the effect of reducing amyloid on CDR-SB score. A range of prior positions were then updated according to Bayes Theorem using these estimates. Results: After updating with new trial data, a wide range of starting positions resulted in credible intervals that did not include no effect of amyloid reduction on CDR-SB. Discussion: For a range of starting beliefs and assuming veracity of underlying data, rational observers would conclude there is a small benefit of amyloid-reductions due to amyloid targeting drugs on cognition. This benefit must be weighed against opportunity cost and side effect risk.