Traumatic brain injury results from an impact to the head that disrupts normal brain function. Traumatic brain injury may affect a person’s cognitive abilities, including learning and thinking skills.
About traumatic brain injury
Falls are the leading cause of traumatic brain injury for all ages. Those aged 75 and older have the highest rates of traumatic brain injury-related hospitalization and death due to falls.
Doctors classify traumatic brain injury as mild, moderate or severe, depending on whether the injury causes unconsciousness, how long unconsciousness lasts and the severity of symptoms. Although most traumatic brain injuries are classified as mild because they're not life-threatening, even a mild traumatic brain injury can have serious and long-lasting effects.
Traumatic brain injury is a threat to cognitive health in two ways:
- A traumatic brain injury's direct effects, which may be long-lasting or even permanent, can include unconsciousness, inability to recall the traumatic event, confusion, difficulty learning and remembering new information, trouble speaking coherently, unsteadiness, lack of coordination, and problems with vision or hearing.
- Certain types of traumatic brain injury may increase the risk of developing Alzheimer's or another form of dementia years after the injury takes place. Learn more.
If a head injury occurs
If you or someone you're with experiences an impact to the head and develops any symptoms of traumatic brain injury, seek medical advice even if symptoms seem mild. Call emergency services for anyone who is unconscious for more than a minute or two or who experiences seizures, repeated vomiting or symptoms that seem to worsen as time passes. Also seek emergency care for anyone whose head was injured during ejection from a vehicle, who was struck by a vehicle while on foot, or who fell from a height of more than 3 feet. Even if you don't lose consciousness and your symptoms clear up quickly, a brain injury still may have occurred.
Symptoms of a brain injury include:
- Inability to remember the cause of the injury or events that occurred immediately before or up to 24 hours after.
- Confusion and disorientation.
- Difficulty remembering new information.
- Blurry vision.
- Nausea and vomiting.
- Ringing in the ears.
- Trouble speaking coherently.
- Changes in emotions or sleep patterns.
The severity of symptoms depends on whether the injury is mild, moderate or severe.
- Mild traumatic brain injury, also known as a concussion, either doesn't knock you out or knocks you out for 30 minutes or less. Symptoms often appear at the time of the injury or soon after, but sometimes may not develop for days or weeks. Mild traumatic brain injury symptoms are usually temporary and clear up within hours, days or weeks, but they can last months or longer.
- Moderate traumatic brain injury causes unconsciousness lasting more than 30 minutes. Symptoms of moderate traumatic brain injury are similar to those of mild traumatic brain injury but more serious and longer-lasting.
- Severe traumatic brain injury knocks you out for more than 24 hours. Symptoms of severe traumatic brain injury are also similar to those of mild traumatic brain injury but more serious and longer-lasting.
Evaluations by health care professionals typically include:
- Questions about the circumstances of the injury.
- Assessment of the person's level of consciousness and confusion.
- Neurological examination to assess memory and thinking, vision, hearing, touch, balance, reflexes, and other indicators of brain function.
Depending on the nature of the traumatic brain injury and the severity of symptoms, brain imaging with computed tomography (CT) may be needed to determine if there's bleeding or swelling in the brain.
Causes and risks
Falls are the most common cause of traumatic brain injury, and falling poses an especially serious risk for older adults. When a senior sustains a traumatic brain injury in a fall, direct effects of the injury may result in long-term cognitive changes, reduced ability to function and changes in emotional health.
Home safety and dementia
Use our online tool, Alzheimer's Navigator®, and get a personalized action list on how to prevent falls and make your home safe for someone with dementia.
Vehicle crashes are another common cause of traumatic brain injury. You can reduce your risk by keeping your vehicle in good repair, following the rules of the road and buckling your seat belt.
Being struck by or colliding with an object, either moving or stationary, is another cause of traumatic brain injury.
Other causes include:
- Indirect forces that jolt the brain violently within the skull, such as shock waves from battlefield explosion.
- Bullet wounds or other injuries that penetrate the skull and brain.
- Sports injuries are also a cause of traumatic brain injury. You can protect your head by wearing a helmet and other protective equipment when biking, inline skating or playing contact sports.
Dementia and traumatic brain injury
Over the past 30 years, research has linked moderate and severe traumatic brain injury to a greater risk of developing Alzheimer's disease or another type of dementia years after the original head injury.
- One of the key studies showing an increased risk found that older adults with a history of moderate traumatic brain injury had a 2.3 times greater risk of developing Alzheimer's than seniors with no history of head injury, and those with a history of severe traumatic brain injury had a 4.5 times greater risk.
- Other studies — but not all — have found a link between moderate and severe traumatic brain injury and elevated risk.
- Emerging evidence suggests that individuals who have experienced repeated traumatic brain injuries (concussions) or multiple blows to the head without loss of consciousness, such as professional athletes and combat veterans, are at higher risk of developing a brain condition called chronic traumatic encephalopathy (CTE) than individuals who have not experienced repeated brain injuries.
- Current research on how traumatic brain injury changes brain chemistry indicates a relationship between traumatic brain injury and hallmark protein abnormalities (beta-amyloid and tau) linked to Alzheimer's.
- Some research suggests that traumatic brain injury may be more likely to cause dementia in individuals who have a variation of the gene for apolipoprotein E (APOE) called APOE-e4. More research is needed to understand the link between APOE-e4 and dementia risk in those who've had a brain injury.
Does every hit to the head lead to dementia?
Not everyone who experiences a head injury develops dementia. There’s no evidence that a single mild traumatic brain injury increases dementia risk. More research is needed to confirm the possible link between brain injury and dementia and to understand why moderate, severe and repeated mild traumatic brain injuries may increase risk.
Treatment and outcomes
The most serious traumatic brain injuries require specialized hospital care and can require months of inpatient rehabilitation. Most traumatic brain injuries are mild and can be managed with either a short hospital stay for observation or at-home monitoring followed by outpatient rehab, if needed.
Treatment of dementia in a person with a history of traumatic brain injuries varies depending on the type of dementia diagnosed. Strategies for treating Alzheimer's or another specific type of dementia are the same for individuals with and without a history of traumatic brain injury.
Alzheimer's disease and other dementias that may occur as a long-term result of traumatic brain injury are progressive disorders that worsen over time. As with all dementias, they affect quality of life, shorten lifespan and complicate the effort to manage other health conditions effectively.
Learn more: Treatment for Dementia, Treatment for Alzheimer's
Dementia help and support are available
The Alzheimer's Association can help you learn more about Alzheimer's and other dementias, and help you find local support services. Call our 24/7 Helpline at 800.272.3900.
Brain Injury Association of America (BIA) is an education, advocacy and research organization that offers support to people with brain injuries and their families. Call their information center at 800.444.6443.
Centers for Disease Control (CDC) has a traumatic brain injury section that offers information about research studies and prevention and education programs.