Memory Digest

Traumatic Brain Injury and CTE

How head injuries—from a single severe blow to many repeated hits—can affect memory and raise dementia risk, what CTE is, and how to protect your brain.

Last reviewed: October 2026

A traumatic brain injury (TBI) happens when a blow, bump or jolt to the head—or an object entering the skull—disrupts how the brain works. Injuries range from a brief concussion to severe damage that changes a person's life.

TBI matters for memory in two ways. First, the injury itself can cause problems with learning, remembering and concentrating. Second, certain types of TBI may raise the risk of dementia years later, according to the Alzheimer's Association. Head injury is one of the modifiable risk factors for dementia—see Reducing Dementia Risk: The 14 Risk Factors.

Mild, moderate and severe

Doctors classify TBI largely by whether a person loses consciousness and for how long:

• Mild TBI (concussion): no loss of consciousness, or unconsciousness lasting 30 minutes or less. Symptoms can include headache, confusion, dizziness, trouble concentrating, and not remembering events just before or after the injury. They usually clear within hours to weeks, but sometimes last months or longer.
• Moderate TBI: unconsciousness lasting more than 30 minutes but less than 24 hours.
• Severe TBI: unconsciousness for more than 24 hours.

In all forms, the Alzheimer's Association notes, changes in thinking are among the most common, disabling and longest-lasting effects. Learning and remembering new information, paying attention, organizing thoughts and planning are often affected.

Falls: the biggest threat for older adults

Falls are the leading cause of TBI, and they are a special danger later in life. The Alzheimer's Association, citing the CDC, reports that about 1 in 4 Americans age 65 and older falls each year. In older adults, even a "minor" fall can cause bleeding inside the skull, especially in people taking blood thinners.

The Alzheimer's Association also notes that older adults who lost consciousness after a TBI were 28% more likely to report memory problems than those who had not had a TBI.

Seek emergency care for anyone who hits their head and is unconscious for more than a minute or two, has seizures, repeated vomiting, worsening headache, increasing confusion or sleepiness, weakness, or slurred speech. Tell the medical team about blood thinners such as warfarin (Coumadin), newer anticoagulants, or aspirin.

TBI and dementia

Researchers describe several ways head injury relates to later dementia:

• Post-traumatic dementia can follow a single, severe TBI. NINDS notes that studies of large populations show moderate or severe TBI in early or mid-life may be associated with increased dementia risk later in life.
• Repeated head injuries may lead to chronic traumatic encephalopathy (CTE), described below.
• Not everyone with a head injury develops dementia—far from it. Risk seems to depend on the severity and number of injuries, age, genetics and overall health.

What is CTE?

Chronic traumatic encephalopathy (CTE) is a progressive brain disorder linked to repeated head impacts, including many that don't cause obvious concussions. According to NINDS:

• CTE develops over years, and symptoms can take years to appear.
• Symptoms may include problems with thinking, understanding and communicating, as well as movement disorders, poor impulse control, depression, confusion and irritability.
• It was first described in boxers and has since been found in athletes in other sports with repeated head impacts, such as football, soccer, rugby and wrestling. Military blast exposure is also being studied.
• CTE was originally identified only at autopsy. Researchers are working on ways to diagnose it in living people, but for now it cannot be confirmed with a simple test during life.

If you or a family member played contact sports or served in combat and now has memory, mood or behavior changes, a doctor can evaluate the symptoms and look for treatable contributors—such as depression, sleep problems, substance use or hormone issues—whatever the underlying cause.

Getting evaluated

After a head injury, or when memory problems appear years later, an evaluation may include:

• A neurological exam (memory, balance, coordination, vision, reflexes)
• CT or MRI scans to look for bleeding, bruising or long-term changes
• Neuropsychological testing to measure memory, attention and problem-solving
• Screening for depression, anxiety and sleep problems, which are common after TBI

See Getting a Diagnosis and Cognitive Screening Tests (MMSE, MoCA).

Recovery and support

Recovery from TBI often continues for months. Helpful approaches include:

• Rest at first, then a gradual return to activity as advised by a clinician
• Cognitive rehabilitation, occupational therapy and speech therapy
• Memory aids such as planners, alarms and checklists—see Memory Aids and Tools
• Treating headaches, sleep problems and mood changes
• Avoiding alcohol and any risk of another head injury while healing

Protecting your brain

Many head injuries can be prevented:

• Wear a seat belt every time, and never drive impaired.
• Wear a helmet for biking, skiing, skating, motorcycling and contact sports.
• Fall-proof your home: good lighting, grab bars, railings on both sides of stairs, no loose rugs—see Home Safety.
• Stay active: strength and balance exercises such as tai chi lower fall risk—see Exercise and the Brain.
• Get vision checked and review medicines that cause dizziness or sleepiness with your doctor—see Medications That Can Affect Memory.

Bottom line

Traumatic brain injury can affect memory right away and may raise dementia risk later, especially after moderate-to-severe or repeated injuries. Falls are the main danger for older adults, and most are preventable. If someone has a head injury, get medical care promptly; if memory or mood changes follow an old injury, talk with a doctor about a full evaluation.

Sources

1. NINDS: Traumatic Brain Injury (TBI)
2. Alzheimer's Association: Traumatic Brain Injury

Not medical advice. This article is general information, not a diagnosis or treatment plan for any individual. Talk with a doctor about your situation.

Related articles

• Reducing Dementia Risk: The 14 Risk Factors
• Home Safety
• What Is Dementia?
• Getting a Diagnosis
• Depression and Memory ("Pseudodementia")