Abstract
Accumulation of brain amyloid beta (Aβ) is a key pathological hallmark of Alzheimer's disease (AD) and begins many years before cognitive symptoms. Being able to predict the risk of Aβ accumulation, or the age at which this accumulation exceeds a critical threshold, may enable early intervention and treatment to slow or prevent the onset of AD. We utilised published genome-wide association studies (GWAS) to develop polygenic scores (PGS) based on AD risk (PGS(risk)) and resilience (PGS(resilience)). We tested whether these could predict (i) whether an individual was an accumulator of Aβ ('Accumulator Status'), and (ii) in accumulators, the age at which brain Aβ is estimated to exceed a threshold of 20 centiloids (CL)('Estimated Age at onset of Aβ'; AAO-Aβ) among 2175 participants (1158 with AAO Aβ) from the Alzheimer's Dementia Onset and Progression in International Cohorts (ADOPIC) study. Additionally, we conducted genome-wide association studies (GWAS) of these traits and developed phenotype-specific PGSs using cross-validation (CV). Higher PGS(risk) was associated with a greater risk of being an accumulator and a younger AAO-Aβ. When stratified by number of APOE ε4 alleles, PGS(risk) predicted Accumulator Status in APOE ε4 heterozygotes, and AAO-Aβ in ε4 non-carriers and heterozygotes, with the same directions of effect as were seen in the whole cohort. PGS(resilience) was not significantly associated with Accumulator Status, but higher PGS(resilience) was associated with later AAO-Aβ overall and in ε4 heterozygotes. Trait-specific PGSs, developed using CV, were not significantly associated with either trait overall and the direction of association varied across CV folds. Polygenic scores, alongside other risk factors, may be useful for identifying individuals at risk of accumulating Aβ, and predicting the age at which this exceeds a critical threshold. This could provide a window for administering disease-modifying treatment or lifestyle interventions to prevent or delay the onset of AD.