Choose your Live Science experience. Get started to get free access to selected news stories, receive our daily newsletter, post comments, play games and earn badges. See what’s in pro. See what's in Pro. No ads on any Live Science articles. No ads on any Live Science articles. Trusted, in-depth, pro-science features that are available only to Pro members. See what's in Pro. Welcome to Live Science club! # A gene variant triples the risk of getting Alzheimer's disease — fat buildup in brain cells may be to blame, study finds. A gene variant called APOE4 is the biggest genetic risk factor for Alzheimer's disease. A gene variant called APOE4 dramatically increases the risk of late-onset Alzheimer's disease, the most common form of dementia. That third thing is the accumulation of droplets of fat, or lipids, in the brain, she told Live Science. A version of the gene called APOE4, which increases the risk of late-onset Alzheimer's three- to 12-fold, makes proteins that are less efficient at this function, Tsai said.