Dale Earnhardt Jr. says he had 20 to 25 concussions during his career

Dale Earnhardt Jr. estimates that he sustained 20 to 25 concussions during his racing career, which he retired from in 2017 after missing half of the previous season due to the neurological effects of a crash.

Earnhardt, whose autobiography “Racing to the Finish: My Story” goes on sale Oct. 16, revealed the remarkable number of injuries during an interview on “In Depth with Graham Bensinger.”

The third-generation NASCAR driver, who is 43, said that he kept the majority of those secret fearing how their reception would affect his career.

“Your brain is your computer and people don’t have the faith in it healing like a broken bone.”

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In an excerpt from the book published in The Charlotte Observer, Earnhardt recounted how after a big crash at Texas Motor Speedway in 2014 he even kept his symptoms secret from his future wife, Amy, and wrote them in a journal on his iPhone instead.

“At first, I don’t think I even really understood why I started doing it. This sounds morbid, but when I look back now I realize that what I was doing was leaving a trail for others to discover in case something happened to me that kept me from being able to tell them myself,” he wrote.

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Earnhardt has pledged to donate his brain to science after his death, and said that he reads about other athletes dealing with the aftermath of concussions and remains concerned about his own future.

“Am I going to have issues with my memory, and my personality? Are those things going to be affected? Are they already affected, and I’m not just aware of it?”

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Gary Gastelu is FoxNews.com's Automotive Editor.