The telephone survey asked if the retirees had ever been diagnosed with dementia, Alzheimer's disease or other memory-related disease. Nearly 2 percent of the former players ages 30 to 49 said yes. That's 19 times the rate for the same age group in the general population.
For retirees over 50, the rate was about five times higher.
Lead author David Weir emphasized the results don't show American football causes memory problems, only that the risk is worth studying. The study of more than 1,000 ex-players was performed by the University of Michigan at the request of the NFL and its Player Care Foundation.