In general, sports that involve an impact on the head can have very serious long-term neurological consequences for those who practice them.
Known for more than 80 years, “boxer’s dementia” is the final phase of a chronic and progressive brain disease, characterized by neurological alteration that is produced by the cumulative effect of repetitive traumatic brain injury. For this reason, the disease is more common in professional boxers, and usually manifests itself several years after the end of their career; Amateur boxers may also experience symptoms and signs of chronic but milder brain damage. Studies have also found brain damage in 99% of football players (American of course (although)).
The original credit for this Answer doesn’t belong to me I’m just a translator, translated from the original post (just translate as it is, nothing changed):