Heritability and rare variant contributions to Alzheimer disease in the Midwestern Amish

The study examined the genetic architecture of Alzheimer's disease in Midwestern Amish communities using extensive pedigree and genomic data. Researchers estimated disease heritability through pedigree analysis and genetic markers. Results showed that common genetic variants explain a large portion of genetic risk in APOE-ε4 carriers, while unexplained risk remains in individuals without this variant. Genome-wide association study confirmed APOE-ε4 as the strongest genetic determinant of Alzheimer's disease in this population. Analysis of rare variants identified genes RIN3 and PILRA as significantly associated with cognitive impairment risk. The research suggests that factors beyond common genetic variants may contribute to disease susceptibility, particularly in individuals without the APOE-ε4 variant.