Microsoft founder Bill Gates said Monday he’s giving $100 million to fight Alzheimer’s disease — $50 million out of his own pocket now, and $50 million later for start-up efforts. Gates said he has a family history of Alzheimer’s, the most common form of dementia, and he also said the condition can wreck the U.S. health care system as more and more people get it. Bill Gates speaks about Alzheimer's in a video published on Nov. 21, 2017. Gates Notes advertisement But mostly, it's because decades of research and billions of dollars of work have failed to produce a cure for the disease, or even to answer basic questions about how and why it develops in the first place. “This is something I know a lot about, because men in my family have suffered from Alzheimer’s,” Gates wrote in his blog. “I know how awful it is to watch people you love struggle as the disease robs them of their mental capacity, and there is nothing you can do about it. It feels a lot like you’re experiencing a gradual death of the person that you knew.” Related: How to Fight Memory Loss More than 5 million Americans have Alzheimer’s, and this number is expected to grow as the population ages. It’s not just devastating to families. It’s expensive, too. I believe that we can alter the course of Alzheimer’s. That’s why I’m investing in the Dementia Discovery Fund. — Bill Gates (@BillGates) November 13, 2017 advertisement “I first became interested in Alzheimer’s because of its costs — both emotional and economic — to families and health care systems,” Gates wrote. “Those who have dementia spend five times more annually on out-of-pocket health expenses than those who don’t have Alzheimer’s, and the disease accounts for direct American health care costs of $259 billion in 2017, with projected growth to $1.1 trillion in 2050,” the Alzheimer’s Association said in a statement. There’s no cure, and treatments do not work well. Drugs such as Aricept, known also as donezepil, can reduce symptoms for a time but they do not slow the worsening of the disease. Drug after drug has failed when tested in patients. advertisement Several compounds can reduce the brain-clogging plaques that