Concussions are the most common form of mild brain injury, affecting over 42 million people worldwide annually. Their long-term risks — especially for athletes and members of the military — are well documented, with studies showing possible connections to neurodegenerative conditions like chronic traumatic encephalopathy and Alzheimer’s disease.

The immediate effects of a concussion are well known, such as alterations in the brain’s structure and activity seen soon after injury. In addition to symptoms like headaches and light sensitivity, a concussion often causes difficulty concentrating or trouble processing new information that can linger for a few weeks before clearing up. But less is understood about how a concussion from earlier in our lives can impact the brain and cognitive health as we age.