Most victims of mild concussions have relatively minor symptoms in the days following the injury, including headaches, dizziness, difficulty concentrating, and vision problems, after which they recover. But a growing body of research reveals potential long-term effects. For example, follow-up studies of over 160,000 head trauma patients over age 65 showed a 22 to 26% increase in the development of dementia during a five to seven-year period after the injury.
Further studies show that concussions have a cumulative effect on those with repeated injuries. For example, football players and boxers with repeated concussions show a 3-times higher rate of deaths due to neurodegenerative diseases including Parkinson’s disease and Alzheimer’s disease.
Repetitive concussions are also associated with Chronic Traumatic Encephalopathy (CTE). This is a progressive neurodegenerative disease similar to Alzheimer’s. In fact, CTE was first identified during a study of the brain of long-time NFL football player, Mike Webster. The scientists identified a specific protein that formed in the brain, similar to that found in Alzheimer's. That substance—known as CTE—has since been identified in 110 brains of football players out of 111 players who donated their brains after death for scientific research.