OSTN and early-onset autosomal dominant Alzheimer disease: In addition to nongenetic factors, we also identified several important genetic risk factors of brain aging in GWAS: the IP6K1 gene encodes a kinase that plays key roles in brain insula function [46], the GMNCgene encodes a protein in cellular processes critical to the development of white matter tracts [32], the OSTN gene restricts activity-dependent dendritic growth as a crucial step in brain development [47], and the SLC25A20 gene has served as a marker of mitochondrial dysfunction in the brain, associated with Alzheimer’s disease [48,49].