“Memory disorders affect many people who never played football or other sports,” Mr. Aiello said. “We are trying to understand it as it relates to our retired players.”

As scrutiny of brain injuries in football players has escalated the past three years, with prominent professionals reporting cognitive problems and academic studies supporting a link more generally, the N.F.L. and its medical committee on concussions have steadfastly denied the existence of reliable data on the issue. The league pledged to pursue its own studies, including the one at the University of Michigan.

Dr. Ira Casson, a co-chairman of the concussions committee who has been the league’s primary voice denying any evidence connecting N.F.L. football and dementia, said: “What I take from this report is there’s a need for further studies to see whether or not this finding is going to pan out, if it’s really there or not. I can see that the respondents believe they have been diagnosed. But the next step is to determine whether that is so.”

The N.F.L. is conducting its own rigorous study of 120 retired players, with results expected within a few years. All neurological examinations are being conducted by Dr. Casson.

According to a 37-page synopsis of the study furnished to the league, the Michigan researchers conducted a phone survey in late 2008 in which 1,063 retired players  those who participated from an original random list of 1,625  were asked questions on a variety of health topics. Players had to have played at least three or four seasons to qualify. Questions were derived from the standard National Health Interview Survey so rates could be compared with those previously collected from the general population, the report said.

Some health issues were reported by N.F.L. retirees at normal rates (kidney and prostate problems), while others were higher (sleep apnea and elevated cholesterol) and others lower (heart attacks and ulcers), the summary said.