Assessment
How a Knock to the Head Can Raise Dementia Risk
A brain injury can have long-term effects. Here’s how to avoid the risk
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Key takeaways
- Falls are a leading cause of traumatic brain injuries in older adults.
- Moderate and severe TBIs are linked to a higher risk of dementia.
- Staying active and preventing falls can help protect brain health.
The scenario is all too common. An older person wakes up at 2 a.m. to go to the bathroom, trips over a lamp wire or the fringe of a throw rug in a dimly lit room, and falls and hits their head on the way down.
Many times, nothing comes of it. But in some cases — more than you may think — these kinds of falls lead to traumatic brain injury, or TBI. A TBI is an injury to the brain caused by a jolt, hit or other outside force.
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One person over the age of 65 falls every second of every day, according to the Centers for Disease Control and Prevention. Each year, more than one in four older adults reports falling. According to the Brain Injury Association of America, about 60 percent of adults who experience a TBI never get medical treatment. Ignoring a TBI can cause problems in both the short and long term.
Falls become more common as we age for several reasons: vision decline, decreased depth perception, and dizziness or drowsiness from medications. And if a head trauma occurs, physical changes in the brain can make the impact more dangerous in older adults.
The long-term effects of TBI
Why is TBI more dangerous for older adults?
- As we age, the brain shrinks slightly, leaving more room for movement inside the skull.
- Blood vessels connecting the brain to the skull become thinner and more prone to rupture.
- Blood thinners prescribed for heart disease, atrial fibrillation or stroke prevention also increase the risk of internal bleeding after a fall or head injury, even when there doesn’t seem to be a wound of any kind.
One important reason to take TBIs seriously and try to avoid them: They put individuals at a higher risk for dementia. According to Dr. Michael Jaffee, chair of neurology at the University of Florida and a board member of the Brain Injury Association of America, studies have found that the risk of dementia is two to three times greater in someone with a moderate TBI and four to five times greater after a severe TBI.
Two years ago, the Lancet Commission report on dementia prevention, intervention and care noted that TBI is one of 14 modifiable risk factors that together account for nearly half of all dementia cases.
One study followed more than 35,000 twins for up to 18 years and made comparisons when one twin had a TBI, and the other did not, suggesting that TBIs that happen at ages 50 to 69 are associated with increased dementia risk. The results were published in Alzheimer’s & Dementia in 2022.
How does TBI boost dementia risk?
Neurologists tend to agree that a TBI can trigger inflammation in the brain and the buildup of amyloid plaques and tau tangles — hallmarks of Alzheimer’s. It can also weaken blood vessels and break down the blood-brain barrier, the network of blood vessels that is a protective shield for the brain.
Emerging evidence also suggests that a TBI can alter the glymphatic system, which clears toxic waste products and harmful proteins from the brain mostly during periods of sleep.
Video: Why TBIs Can Be More Dangerous in Older Adults
But not everyone responds to a TBI the same way. Overall physical and cognitive health play a role. Some people who experience a TBI have cognitive reserve — the brain’s ability to adapt and keep functioning despite an injury. Individuals with a strong cognitive reserve have an extra mental buffer that may allow them to better withstand the effects of neurological deterioration in the wake of a TBI.
“Some evidence suggests that the severity of the TBI, the number of TBIs a person has sustained over their lifetime, older age at injury and other individual and environmental factors can influence the risk of dementia after TBI,” says Kristen Dams-O'Connor, director of the Brain Injury Research Center of Mount Sinai in New York.
“It is possible that a TBI in late life accelerates the progression of changes in the brain that were already underway,” Dams-O’Connor says. “It is also possible that a person was showing little or no signs of clinical dementia prior to the TBI, and the TBI essentially takes away the cognitive reserve that was preventing the disease from dramatically impacting clinical function.”
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Can you cut your risk of TBI-related dementia?
The simplest way to cut your risk is to prevent the falls that lead to a brain injury and minimize the damage of a fall if you do have one.
- Remain active, both physically and cognitively. Core strengthening and maintaining a strong and steady gait are both important for fall prevention. Here’s a move to help with balance.
- Reduce fall risk in your home. Remove clutter and objects on the floor, secure rugs, wear sturdy shoes and ensure spaces are well lit.
- If you are unsteady or have mobility problems, use physical aids like grab bars in the bathroom and shower and handrails on the stairs. Use a cane or walker if your doctor recommends it.
- When starting new medications, ask your doctor if they can cause dizziness or imbalance, either alone or in combination with other drugs.
- Have your vision and hearing checked regularly and corrected if necessary. Vision and hearing loss are both, on their own, risk factors for dementia. Once a year, AARP members can take The National Hearing Test for free.
- Take your time when getting up from a chair or bed.
What to do if you fall
If you do hit your head, you may have reason to err on the side of caution and go to an emergency room or see your own doctor, even if you experience very few symptoms. This is especially true if you’re on blood thinners.
TBI symptoms may include dizziness, sleep disruption, changes in mood and irritability, memory issues, or a feeling of fogginess. But it’s not unusual to have a TBI and never lose consciousness or show only a small bump on your head.
“Symptoms can have a snowball effect,” Jaffee says. He advises taking brain health measures that allow for better resilience, which helps if a traumatic brain injury occurs. He adds that “nutrition, exercise and social connections, are all things that can help minimize the problem if you have a TBI.” Getting good sleep is also crucial.
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