Alzheimer's disease genetics converges on microglial and neuronal dysregulation

Alzheimer’s disease (AD) is the most common cause of dementia, with global case numbers projected to reach 153 million in 20501. AD is highly heritable, with twin-based heritability estimates of 60–80%2. Although 1,200 causal loci are predicted to exist for AD3, approximately 80 loci have been associated with AD in two recent studies4,5. Low single-nucleotide polymorphism (SNP)-based heritability estimates have prompted the suggestion that little further common-variant risk remains to be found6. Here we analysed data from 109,479 cases, 74,141 proxy cases, 2,131,799 controls and 499,708 proxy controls from diverse ancestries, identifying 118 loci in a multi-ancestry analysis and 9 additional loci in ancestry-specific analyses, 48 of which are new. We identified new AD risk genes, prioritized potential drug targets, and found that genes upregulated in microglia and downregulated in neurons in cases compared with controls were enriched for AD-associated genetic risk. Moreover, we improved polygenic prediction and estimated a SNP heritability of 16%, nearly threefold higher than previous estimates. Together, our findings show that the common-variant contribution to AD has been substantially underestimated, and reveal new molecular and cellular mechanisms as well as specific targets for future drug development research.