While the causes for Parkinson’s are largely unknown, a 2020 study revealed a link between concussions and brain and neurological diseases like Parkinson’s and dementia. The study by the Family Medicine and Community Health noted that having a single concussion increased the risk of developing Parkinson’s by 57% and dementia by 72%.

Here’s what we know about Favre’s concussion history in the NFL:

How many concussions did Brett Favre have during his NFL career?

In a 2018 interview on “Megyn Kelly Today,” Favre said he had “three or four” concussions that he was aware of during his playing career but estimated the actual total to be much higher.

Favre added: “As we’re learning about concussions, there’s a term that’s often used in football and other sports. … I got dinged. As Doctor (Bennet) Omalu, who was portrayed by Will Smith in the movie ‘Concussion,’ explained, ‘dinged’ is a concussion when you have ringing of the ears, seeing stars. That’s a concussion and, if that’s a concussion, I’ve had hundreds, probably thousands throughout my career, which is frightening.”