Brett Favre’s announcement that he has Parkinson’s disease is bringing renewed attention to the potential links between football and a risk of brain disease.

Brett Favres Parkinsons diagnosis raises concerns about footballs link to brain disease and the risks of repeated head injuries in contact sports

Mr. Favre, the former N.F.L. quarterback who fell from grace after Mississippi officials accused him of helping divert funds meant for low-income residents, announced the diagnosis before Congress.