Finally, we estimated the additional years of independence in IADLs and BADLs associated with lecanemab treatment or donanemab treatment due to the slower rate of decline in CDR‐SB (Figure 3). To do this, we assumed that disease progression in each arm (placebo and treatment) was linear both during and after the trial period, with a slope based on the observed effect at the end of the trial. The lecanemab trial found an average annual progression in CDR‐SB for the placebo group of 1.11 (based on the published 18‐month ∆CDR‐SB of 1.66), with treatment decreasing this progression by 0.3 (95% CI 0.15–0.45, based on the published 18‐month decrease in ∆CDR‐SB by 0.45). 1 Assuming these effects are constant over the course of treatment, those with baseline CDR‐SB = 2 would be expected to have an additional 10 months of independence in IADLs on lecanemab (95% CI 4–18 months, Figure 3A).
