I became interested in traumatic brain injury and concussion after seeing firsthand how disruptive a concussion can be.
A concussion is a form of mild traumatic brain injury (TBI). It can result from a blow or jolt to the head—or from a force to the body that causes the brain to move rapidly inside the skull. Symptoms can affect thinking, memory, balance, mood, sleep, vision, and physical well-being.
Most people recover from a concussion, often within days or weeks, but recovery varies. Some people experience symptoms that persist much longer. Current guidance generally favors a gradual return to normal activity after a brief period of relative rest, rather than prolonged complete rest.
I am also interested in the longer-term question: Can head injuries increase the risk of cognitive decline or dementia later in life? Research has linked moderate or severe traumatic brain injury and repeated head impacts with increased risk of later neurological problems. However, a single uncomplicated concussion should not be assumed to cause Alzheimer’s disease or dementia.
This page looks at recognizing concussion, recovery and return to activity, persistent symptoms, repeated head injuries, and what is known—and still uncertain—about TBI, CTE, and dementia.
Most people recover well from a concussion, but recovery time varies. Symptoms can affect thinking, memory, balance, mood, sleep, and physical well-being. A gradual return to normal activity is generally recommended after a short period of relative rest.
Repeated concussions and more serious traumatic brain injuries deserve particular attention. Moderate or severe TBI is associated with an increased risk of cognitive decline and dementia later in life.
Repeated head impacts have also been associated with chronic traumatic encephalopathy (CTE), although important questions remain about who develops it and why.
Preventing head injuries, recognizing concussion, and managing recovery appropriately are important parts of protecting long-term brain health.
A concussion can occur after a blow to the head, a fall, a sports collision, or another impact that causes the brain to move rapidly inside the skull. A person does not have to lose consciousness to have a concussion.
Symptoms may appear immediately or develop over the following hours. Common symptoms include headache, dizziness, nausea, balance problems, sensitivity to light or noise, blurred vision, fatigue, difficulty concentrating, memory problems, irritability, and changes in sleep.
Some people describe feeling mentally slowed down, confused, or “in a fog.”
Certain symptoms after a head injury require urgent medical attention. These include a worsening severe headache, repeated vomiting, seizures, increasing confusion or unusual behavior, weakness or numbness, slurred speech, one pupil larger than the other, inability to stay awake, or loss of consciousness.
When a concussion is suspected, the person should be removed from sports or other activities where another head injury could occur and medically evaluated.
Concussion treatment has changed considerably. In the past, people were often advised to rest completely until all symptoms disappeared. Current guidance generally recommends relative rest for the first day or two, followed by a gradual return to normal activities as tolerated.
Light physical activity, such as walking, can often begin fairly early if it does not significantly worsen symptoms. School, work, exercise, and other activities can then be increased gradually.
An athlete with a suspected concussion should not return to play the same day. Returning to sports should occur gradually, with progressively more demanding activity and appropriate medical guidance.
This is particularly important because another head injury before the brain has recovered can prolong recovery and, rarely, lead to serious complications.
Most people improve substantially within days or weeks, but some experience headaches, dizziness, difficulty concentrating, sleep problems, fatigue, or other symptoms for much longer.
Persistent symptoms deserve further evaluation. Treatment may address specific problems such as balance and dizziness, headaches, vision difficulties, sleep, mood, or exercise intolerance rather than simply prescribing more rest.
One of the most important questions is whether head injuries can affect the brain years or even decades later.
Research has found that people who have experienced moderate or severe traumatic brain injury have an increased risk of developing cognitive impairment and dementia later in life. The relationship is less clear after a single uncomplicated concussion.
Repeated concussions and repeated exposure to head impacts are a greater concern, particularly among people who have participated for many years in collision sports or had other repeated head trauma.
Chronic traumatic encephalopathy (CTE) is a degenerative brain disease associated with a history of repeated head impacts. It has been identified after death in some former athletes and others with substantial exposure to repetitive head trauma.
Researchers are still trying to determine how common CTE is, why some people with repeated head impacts develop it while others do not, and how the risk relates to the number, severity, and timing of head impacts.
CTE currently can be definitively diagnosed only by examining brain tissue after death. Research is underway to develop reliable ways to identify it during life.
The practical message is clearer than many of the unanswered scientific questions: preventing repeated head injuries and allowing adequate recovery after concussion are important for protecting brain health.
Large studies have found an association between traumatic brain injury and later dementia, although the size of the risk varies considerably depending on the severity and number of injuries, age, and the population studied.
The Alzheimer’s Association’s 2026 Facts and Figures report estimates that experiencing a moderate or severe TBI is associated with roughly two to four times the risk of dementia compared with people without such injuries. Risk also appears to increase with repeated TBIs.
A large study of more than 160,000 older adults found that moderate-to-severe TBI was associated with increased dementia risk at every age studied. The relationship between a single mild TBI and dementia was less consistent and appeared to vary with age.
Importantly, an increased risk is not a prediction of what will happen to an individual. Most people who have had a concussion will not necessarily develop dementia, and many other factors—including age, genetics, cardiovascular and metabolic health, and lifestyle—also influence dementia risk.
The research does, however, provide another reason to prevent head injuries and repeated concussions whenever possible.
Researchers are studying whether nutrition and certain supplements can help the brain recover after concussion or traumatic brain injury.
Omega-3 fatty acids, particularly DHA, are of special interest because DHA is an important component of brain-cell membranes and omega-3s have anti-inflammatory effects. Early human research is encouraging, but there is not yet enough evidence to recommend omega-3 supplements as a proven treatment for concussion.
Vitamin D is also being studied. Maintaining an adequate vitamin D level is important for general health, and correcting a deficiency is reasonable. Some research suggests that vitamin D deficiency may be associated with poorer recovery after TBI, but vitamin D supplementation has not been established as a specific treatment for concussion.
Other supplements—including magnesium, riboflavin, melatonin, and several antioxidants—are also being investigated, but the evidence remains preliminary.
For now, the best-supported approach is to maintain adequate nutrition and correct documented nutritional deficiencies, while viewing supplements as an area of promising research rather than established concussion therapy.
Not every head injury can be prevented, but some risks can be reduced.
For children and adults, this includes using appropriate helmets and protective equipment, wearing seat belts, following sports concussion protocols, and avoiding a return to activities where another head injury could occur before recovery.
For older adults, preventing falls becomes particularly important. Strength and balance training, reviewing medications that may contribute to dizziness, correcting vision problems, and reducing fall hazards in the home can all help.
Good overall brain health also matters after a TBI. Regular physical activity, adequate sleep, avoiding smoking, maintaining cardiovascular and metabolic health, and staying socially and mentally engaged are sensible measures for brain health generally, although they have not been proven to eliminate the increased dementia risk associated with a significant TBI.
The goal is straightforward: protect the brain from the injuries we can prevent and take the injuries that do occur seriously.
The Centers for Disease Control and Prevention (CDC) provides practical information about concussion, including signs and symptoms, recovery, returning to school and sports, prevention, and when to seek medical care. Its HEADS UP program is particularly useful for parents, athletes, coaches, and schools.
The Brain Injury Association of America (BIAA) provides information and support for people with brain injuries and their families. Its resources cover concussion, recovery, rehabilitation, persistent symptoms, and living with brain injury.
The Alzheimer’s Association explains what researchers know about the relationship between traumatic brain injury, repeated head injuries, cognitive decline, and dementia. It is particularly useful for understanding the longer-term questions discussed on this page.