The genetic architecture of Alzheimer disease risk in the Ohio and Indiana Amish

Alzheimer disease (AD) is the most common type of dementia and is currently estimated to affect 6.2 million Americans. It ranks as the sixth leading cause of death in the United States and the proportion of deaths due to AD has been increasing since the year 2000 while the proportion of many other leading causes of deaths have decreased or remained constant. The risk for AD is multifactorial, including genetic and environmental risk factors. Though APOE remains the largest genetic risk factor for AD, more than 26 other loci have been associated with AD risk. Here, we recruited from a population of Amish adults from Ohio and Indiana to investigate AD risk and protective genetic effects. With slightly lower incidence and later age of onset, it is thought that the Amish may hold protective genetic variants for AD. As a founder population that typically practices endogamy, variants that are rare in the general population may be at higher frequency in the Amish population. We characterized the genetic architecture of AD risk in the Amish and compared this to a non-Amish population, elucidating the lower relative importance of APOE and differing genetic architecture of the Amish compared to a general European ancestry population.