Head injuries can raise the risk of dementia, with studies showing people who have had a traumatic brain injury are up to two times more likely to develop it later in life. This link holds true even for mild injuries, and it affects groups like older adults, athletes, and military veterans.
A traumatic brain injury, or TBI, happens when a blow to the head disrupts normal brain function. It can range from mild concussions to severe damage. Research points to TBI as one of several factors that contribute to dementia worldwide. Experts estimate it plays a role in about 3 percent of all dementia cases globally. People with a history of TBI face roughly a 50 percent higher chance, or 1.5 times the risk, compared to those without.[1][2]
The connection appears stronger in certain people. For older adults, a TBI leads to higher death rates in the months after the injury, especially if they already had dementia before the head trauma. Those with pre-existing dementia see even worse long-term outcomes, with risks climbing at six and twelve months post-injury. Military veterans with mild TBI from post-9/11 conflicts have double the dementia risk compared to veterans without such injuries.[1][3]
Sports and repetitive head impacts add to the concern. Repeated blows, like those from heading a soccer ball or tackles in football, may speed up brain changes linked to dementia. One rare type tied to these injuries is chronic traumatic encephalopathy, or CTE, found in some former athletes’ brains after death. Scientists are studying how even a single mild injury can trigger harmful processes, such as brain inflammation or the spread of faulty proteins.[2][4][5][6]
New findings explain some reasons behind this risk. A mild brain injury can disrupt the brain’s natural drainage system, allowing toxic proteins to build up, much like in Alzheimer’s disease. Both TBI and Alzheimer’s involve similar abnormal proteins called tau, which may worsen over time after injury. Brain contusions from trauma also contain materials that could spread disease-like changes to other brain areas.[5][6][7]
Protecting the head through helmets, rules in sports, and quick medical care after any injury may help lower these risks. Ongoing studies look at blood flow changes from heading in soccer players and particles released after impacts in American football to spot early warning signs.[2]
Sources
https://pmc.ncbi.nlm.nih.gov/articles/PMC12676572/
https://www.alzheimersresearchuk.org/about-us/our-influence/policy-work/position-statements/sport-and-dementia/
https://jamanetwork.com/journals/jamanetworkopen/fullarticle/2842588
https://pubmed.ncbi.nlm.nih.gov/41453070/?fc=None&ff=20251227142304&v=2.18.0.post22+67771e2
https://onlinelibrary.wiley.com/doi/10.1002/ana.78132?af=R
https://nrtimes.co.uk/research-reveals-why-mild-brain-injury-can-trigger-alzheimers-hnc25/
https://www.news-medical.net/news/20251216/Traumatic-brain-injury-disrupts-brain-drainage-and-accelerates-Alzheimere28099s-risk.aspx
