Traumatic brain injury may increase risk of cognitive decline
Whether it's due to slipping on an icy sidewalk, a sports-related collision or even a mishap on the playground, bumps to the head are common. But when are they serious?
According to the Centers for Disease Control and Prevention (CDC), more than 200,000 people are hospitalized annually in the U.S. due to traumatic brain injury (TBI) — broadly defined as an impact that disrupts normal brain function. Beyond the immediate effects of the injury, research suggests that TBI may also increase future risk of cognitive decline. Taking steps to protect your head today may lower your risk of dementia tomorrow.
While there are many variables in TBI and currently no way of knowing which injuries might lead to dementia, researchers have found evidence of a relationship between the severity of TBI and increased risk of cognitive decline.
Doctors typically classify TBIs as mild, moderate or severe. In moderate and severe cases, a person may experience prolonged loss of consciousness, amnesia and bleeding in the brain. Most cases of TBI are considered mild because they're not life-threatening, with common symptoms including confusion, dizziness and vision problems. But even mild TBIs may have lasting repercussions.
"Traumatic brain injury of any magnitude increases the risk for cognitive decline later in life," says Ann McKee, M.D., director of the Boston University Alzheimer's Disease Research and Chronic Traumatic Encephalopathy (CTE) Centers and a leading expert in neurology and neuropathology — whose research has advanced insight on the risks of repetitive mild TBIs. "We've known that about moderate and severe TBI, but now it's been shown for milder forms, too. The type that's sometimes symptomatic like a concussion, but very often asymptomatic — an invisible injury. The person may shrug it off."
In all forms of TBI, cognitive changes (changes in how people think) are among the most common, most disabling and longest-lasting symptoms. The severity of symptoms depends on whether the injury is mild, moderate or severe.
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More recent research suggests that mild TBIs sustained repeatedly over time may cause injury, McKee says. "What we've shown with our work is that the duration of exposure to these repetitive hits is associated with risk for [a type of] neurodegenerative disease that eventually causes cognitive decline and dementia as you age."
While everyone, young and old, is vulnerable to TBI, there are factors that put some people at greater risk. The leading causes of TBI that result in emergency room visits are falls and car accidents. Falls are especially dangerous for older adults, with 1 in 4 Americans over 65 reporting a fall each year.
According to Bruce Lamb, Ph.D., executive director of the Paul and Carole Stark Neurosciences Research Institute, the danger may be compounded for an older adult who is already living with dementia. "TBI in an individual already living with cognitive decline can potentially exacerbate existing cognitive deficits," Lamb says, adding that subsequent injuries can lead to worsened outcomes. "Avoiding the risk of future TBIs after an initial incident is of high importance."
Fortunately, simple actions like wearing a seat belt in the car or a high-quality helmet while riding a bike or playing sports can help lower the risk of TBI. For older adults, there are a number of ways to reduce the likelihood of falling, such as wearing appropriate footwear, using a walker if needed, ensuring prescription eyeglasses are up-to-date, and removing potential tripping hazards in the home, like loose floor rugs.
But accidents happen. If you or someone you know has experienced a head injury, it's important to get checked out by a doctor right away. TBI can affect your brain even if you don't lose consciousness, and while symptoms may be minimal or clear up quickly, the injury may still be severe. Health care professionals can evaluate symptoms, perform other tests and help with recovery.
Not every hit to the head will result in a TBI and not every TBI will increase risk of cognitive decline, but the impact of such injuries can be varied and long-lasting.
McKee encourages people to pay attention to their bodies and advocate for themselves in health care settings if they experience lingering symptoms.
"One size doesn't fit all. TBI takes many forms in different people and it can have many different effects," McKee says.
Learn more about the risks of brain injury at alz.org/TBI.