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Traumatic Brain Injury (TBI): Can It Cause Dementia?

What is traumatic brain injury?

Traumatic brain injury (TBI) results from a sudden, external, violent blow to the head that damages the brain, disrupting normal brain functioning. TBI is a broad term that refers to a wide range of brain injuries. It can affect an individual’s cognitive abilities, including memory, thinking, and learning.

Experts classify TBI as mild, moderate, or severe based on whether the injury induces unconsciousness, the duration of unconsciousness, and the severity of symptoms. Since most brain injuries are non-fatal, they display mild symptoms. However, even minor traumatic brain injuries can have catastrophic and long-term consequences.

According to statistics, most of the TBI cases (about 40%) are due to falls followed by unintentional blunt trauma (15%) and motor vehicle accidents (14%).

What are the types of TBI?

There are two types of traumatic brain injuries.

  • Closed brain injury occurs due to non-penetrating injury with no skull breakage. Rapid forward or backward movement or indirect violent jolts to the brain within the skull can cause this type of TBI due to the tearing and bruising of brain tissues and blood vessels. Falls, car accidents, and sports head injuries are the leading causes of closed brain injury.
  • Penetrating brain injury (also known as open head injury) results when there is a break in the skull, for instance, when a bullet pierces the skull and brain.

How can TBI impact cognitive health?

Traumatic brain injury, which occurs as a result of a blow to the head and affects normal brain function, endangers cognitive health in two ways:

  • The direct effects of TBI might include unconsciousness, disorientation, inability to recollect traumatic events, trouble learning and retaining new information, difficulty speaking, lack of coordination, and visual or hearing problems. These can be long-lasting or even permanent.
  • Some forms of TBI may raise the likelihood of acquiring Alzheimer’s or another type of dementia years later.

Is there any connection between Traumatic Brain Injury and Dementia?

Over the last three decades, research has connected moderate and severe traumatic brain injury to an increased risk of getting Alzheimer’s disease or another dementia years later. According to a study, the higher the severity of the head injury, the higher the Alzheimer’s risk. Seniors with a history of moderate brain injury had a 2.3 times greater risk of developing Alzheimer’s than seniors with no TBI history. Furthermore, those with a history of severe brain injury had an even higher (about 4.5 times) risk. Some other studies (but not all) have also suggested a similar connection between moderate and severe TBI and increased risk.

Increased Risk of TES/CTE

There is no proof that a single moderate TBI raises the risk of dementia. However, the emerging evidence does demonstrate that the chance of developing traumatic encephalopathy syndrome (TES) or specific brain alterations linked to chronic traumatic encephalopathy (CTE) may increase with repeated mild traumatic brain injuries, such as those that can occur in sports like American football, hockey, boxing, and soccer.

Symptoms of TES/CTE include memory loss, disorientation, impaired judgment, anger, depression, anxiety, suicidality, parkinsonism, and progressive dementia. These symptoms may manifest years or even decades later after the last brain injury.

Previous studies have demonstrated that boxers are more likely to experience particular brain alterations linked to CTE and may also experience impairments in cognition. The likelihood of the specific CTE-associated brain changes in boxers appears to correspond with the number of rounds boxed rather than the number of knockouts. It implies that even repeated mild traumatic brain injuries that do not render a person unconscious may increase the risk of dementia. CTE-associated brain changes CTE can occur after a small number of severe TBIs, a large number of mild or very TBIs, or some other pattern of head trauma.

TBI is a risk factor for dementia

Researchers in Sweden have also reported that TBI is a risk factor for dementia, revealing that the likelihood of receiving a dementia diagnosis was highest in the first year following the injury. During this time, dementia diagnoses were four to six times more likely to occur in TBI patients than in the general population. The study also concluded that there might be a risk of dementia even 30 years after a concussion or other TBI.

Having a history of TBI may accelerate dementia

According to a study published in 2016, a history of TBI may cause cognitive impairment to appear two or more years earlier than it would otherwise. These findings were commensurate with other studies that found TBI to be a substantial risk factor for cognitive decline in older adults and associated with the beginning of moderate cognitive impairment and Alzheimer’s disease at a younger age.

Similar brain changes in Alzheimer’s and mild TBI

A recent study revealed similarities in the brain changes in people with Alzheimer’s disease and mild TBI. The brains of Alzheimer’s and TBI individuals exhibited a reduced cortical thickness in comparison with healthy individuals. Experts frequently associate cortical thinning with a decline in memory, verbal fluency, the ability to integrate new knowledge, and the capacity to make judgments.

The link between TBI and APOE ε4 gene

The APOE ε4 gene is associated with the onset of Alzheimer’s disease. Some studies have indicated that in individuals with an APOE ε4 variant of the apolipoprotein E (APOE) gene, TBI may be more likely to increase the risk of Alzheimer’s. However, more research is required to fully understand the association between APOE ε4 and dementia risk in people who have experienced a traumatic brain injury.

More research is needed to understand the connection between TBI and dementia

More research is required to fully comprehend the connection between TBI and dementia and why people who have experienced moderate, severe, or repeated mild traumatic brain injuries are more likely to experience alterations in their memory, thinking, and reasoning later in life.

What are the symptoms of TBI?

Whether the injury is mild, moderate, or severe will determine how severe the symptoms are. Among all forms of TBI, cognitive changes are the most prevalent, disabling, and persistent effects of the injury. It also frequently impacts the ability to learn and remember new information, pay attention, organize thoughts, develop efficient strategies for completing tasks and activities and make sound judgments. Years after the damage and the person seems to have recovered from its initial consequences, more severe cognitive abnormalities (which are a hallmark of dementia) may arise.

Mild TBI or concussion may or may not cause unconsciousness. Its symptoms may include headache, dizziness, confusion, disorientation, blurry vision, nausea and vomiting, problem finding words, sensitivity to light or sound, trouble speaking clearly, and changes in energy, emotions, or sleep patterns. Unconsciousness may last for 30 minutes or less, and a person may be unable to remember the circumstances leading up to the injury or those that happened within 24 hours.

In moderate TBI, unconsciousness lasts more than 30 minutes but less than 24 hours, while in severe TBI, it lasts more than 24 hours. Their symptoms are similar to mild TBI but are graver and longer-lasting.

How to prevent traumatic brain injury?

Falls are the most common cause of TBI. The following measures can help prevent falls:

  • Utilize a walker or other aid to compensate for muscle weakness, poor balance, or mobility issues.
  • Get your vision examined regularly and use contact lenses or glasses for correcting changes.
  • Prevent domestic dangers like clutter, loose rugs, and poor lighting.

You can also take other precautions to prevent traumatic brain injury, such as wearing a helmet or other protective gear to protect your head while biking or playing contact sports,
maintaining your vehicle to keep it in good condition, following road and traffic rules, and fastening your seat belt.

References

1. Dementia in Head Injury. https://www.webmd.com/alzheimers/dementia-head-injury

2. Gottlieb, S., 2000. Head injury doubles the risk of Alzheimer’s disease. BMJ, 321(7269), p.1100. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1173459/

3. McCrory, P., Zazryn, T. and Cameron, P., 2007. The evidence for chronic traumatic encephalopathy in boxing. Sports medicine, 37(6), pp.467-476. https://pubmed.ncbi.nlm.nih.gov/17503873/

4. Nordström, A. and Nordström, P., 2018. Traumatic brain injury and the risk of dementia diagnosis: A nationwide cohort study. PLoS medicine, 15(1), p.e1002496. https://pubmed.ncbi.nlm.nih.gov/29381704/

5. Li, W., Risacher, S.L., McAllister, T.W. and Saykin, A.J., 2016. Traumatic brain injury and age at onset of cognitive impairment in older adults. Journal of neurology, 263(7), pp.1280-1285. https://pubmed.ncbi.nlm.nih.gov/27007484/

6. Rostowsky, K.A. and Irimia, A., 2021. Acute cognitive impairment after traumatic brain injury predicts the occurrence of brain atrophy patterns similar to those observed in Alzheimer’s disease. GeroScience, 43(4), pp.2015-2039. https://pubmed.ncbi.nlm.nih.gov/33900530/

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