Using subjective cognitive decline to identify high global amyloid in community‐based samples: A cross‐cohort study

Introduction We aimed to examine the contribution of subjective cognitive decline (SCD) to reduce the number of β‐amyloid (Aβ) positron emission tomography scans required for recruiting Aβ+ clinically normal individuals in clinical trials. Methods Three independent cohorts (890 clinically normal: 72 yrs ± 6.7; Female: 43.4%; SCD+: 24%; apolipoprotein E [ APOE ] ε4+: 28.5%; Aβ+: 32%) were used. SCD was dichotomized from one question. Using logistic regression, we classified Aβ+ using the SCD dichotomy, APOE ε4, sex, and age. Results SCD increased odds of Aβ+ by 1.58 relative to non‐SCD. Female APOE ε4 carriers with SCD exhibited higher odds of Aβ+ (OR = 3.34), whereas male carriers with SCD showed a weaker, opposing effect (OR = 0.37). SCD endorsement reduces the number of Aβ positron emission tomography scans to recruit Aβ+ individuals by 13% and by 9% if APOE ε4 status is known. Conclusion SCD helps to classify those with high Aβ, even beyond the substantial effect of APOE genotype. Collecting SCD is a feasible method for targeting recruitment for those likely on the AD trajectory.