A new report from the Alzheimer’s Association says that as many as 5 million Americans have Alzheimer’s disease or some other form of dementia. Every 67 seconds someone in the United States develops Alzheimer’s disease or dementia. That’s 470,000 Americans this year alone. Given that these thieves of memory and personality are so common and so feared, should all older Americans be tested for them? In proposed guidelines released yesterday, the U.S. Preventive Services Task Force said “no.” Why not? Even after conducting a thorough review of the evidence, the panel said that there isn’t enough solid evidence to recommend screening, especially since not enough is known about the benefits and the harms. In part, the recommendation is based on the sad fact that so far there aren’t any truly effective approaches to stop the forward progress of dementia.