Genetic Variation Underlying Traumatic Brain Injury and Late-Onset Alzheimer's disease Lead Investigator: Sandra Barral Institution : Columbia U E-Mail : smb2174@cumc.columbia.edu Proposal ID : 738 Proposal Description: Our proposal has two main goals, first, to provide a better understanding of the genetic architecture and the underlying association between Traumatic Brain Injury (TBI) and Late-Onset Alzheimer???s Disease (LOAD) and second, to aid in the need of diagnostic test to detect the progression to AD and subsequent TBI. There is a significant deficit in the literature investigating the possible association between Traumatic Brain Injury (TBI) and increased susceptibility to develop Late-Onset Alzheimer???s Disease (LOAD) later in life. Genetic variation has been investigated as a potential modulator of association between (TBI) and increased susceptibility to develop LOAD later in life, however, no specific genes have been discovered. Identifying individuals at higher risk of developing AD after TBI (carriers of the identified high risk genetic variants), will aid the prognosis and early detection of disease and subsequent therapeutic decisions. We hypothesize that genetic risk factors interact with exposure to TBI to modify risk of LOAD. Our specific aims for this proposal are: ??? To characterize trajectories of memory change in subjects stratified by LOAD and TBI status using the longitudinal data in 4,878 samples from the National Alzheimer Coordinating Center (NACC). ??? To identify genes that interact with TBI and modify risk associated with LOAD using a genome-wide gene-based interaction approach. o To identify genome-wide TBI-interacting genes that predict risk of LOAD using the non-stratified sample from the National Alzheimer Coordinating Center (NACC). o To assess nominally significan