A Traumatic brain injury (TBI) is typically caused by a forceful blow or jolt to the head or body. Traumatic brain injury can also be caused by an object that passes through brain tissue, such as a gunshot or fractured piece of skull. 

Over the last 30 years, research has connected moderate and severe TBI to an increased risk of cognitive decline or dementia years later. According to studies, older people with a history of moderate TBI had a 2.3 times greater chance of getting Alzheimer’s than seniors without a history of head injury. Those who had a history of severe TBI were at 4.5 times higher risk. 

Multiple epidemiologic studies demonstrate that having TBI in early or midlife relates to an elevated risk of dementia in later life, making dementia one of the most feared long-term outcomes of TBIs. The best evidence suggests that moderate and severe TBIs raise the risk of dementia by 2 to 4 times. It is less apparent if minor TBIs, such as brief concussions, increase the incidence of dementia, in part because light head injuries are frequently not well recorded and retrospective studies include recall bias.  

In a study published by the Journal of Neurology, Wei Li and colleagues found that a history of TBI may accelerate the age of onset of cognitive impairment by 2 or more years. These results were consistent with other studies that indicate TBI is a significant risk factor for cognitive decline in older adults and is associated with an earlier age of onset in people with mild cognitive impairment and Alzheimer’s disease. 

Traumatic brain injury may be more likely to increase the risk of dementia in individuals who have a specific variant of the gene for apolipoprotein E (APOE) called APOE-e4.   

How might a head injury or TBI cause dementia?

TBIs, or severe head traumas, can damage the brain, resulting in a variety of cognitive deficits such as memory loss, trouble with language and communication, confusion, and behavioral disorders. These cognitive deficits can progress and evolve into dementia in some cases over time. Various types of bleeding and tearing forces harm nerve fibers and produce inflammation, metabolic alterations, and brain edema as primary impacts on the brain. 

Diffuse Axonal Injury (DAI)

One of the most prevalent types of brain traumas is diffuse axonal injury (DAI), which refers to widespread damage to the brain’s white matter. This type of damage is widespread in car accidents, falls, and sports injuries. DAI has the ability to disrupt and break down communication between nerve cells (neurons) in the brain. It also causes the release of brain chemicals, which might cause more damage.  


A concussion is a sort of mild TBI that may be considered a transitory brain injury but might take minutes to months to heal. A bump, blow, or shock to the head, sports injury or fall, motor vehicle accident, weapons discharge, or rapid acceleration or deceleration of the brain within the skull, such as the person being forcibly shaken, can all produce concussion. 


Contusions are bruising or swelling of the brain caused by the hemorrhage of extremely minute blood arteries into brain tissue. Contusions can occur directly beneath the point of hit or, more commonly, on the opposite side of the brain from the point of impact. They can occur after several hours to a day’s delay. 

Skull Fractures

Skull fractures are breaks or cracks in one or more of the skull’s bones. They are caused by blunt force trauma and can harm the membranes, blood vessels, and brain behind the fracture. One major advantage of helmets is that they help to avoid skull fractures. 

Severe TBI

A single severe TBI can potentially cause post-traumatic dementia (PTD), which can be progressive and shares certain characteristics with CTE. Studies of large populations of persons with TBI show that moderate or severe TBI in early or mid-life is related to an elevated risk of dementia later in life. 


Hematomas are areas of bleeding in and around the brain caused by a blood vessel rupture. Different forms of hematomas arise based on where the blood gathers in relation to the meninges, which are three layers of protective membranes covering the brain: dura mater (outermost), arachnoid mater (middle), and pia mater (innermost). 

TBI-related brain damage can be localized to a single part of the brain, known as a focal injury, or it can occur over a larger area, known as a diffuse injury. The nature of the injury also influences how the brain is harmed. 

Are all head injuries or TBIs linked to dementia?

No! Not all TBIs or brain traumas result in dementia. The risk of acquiring dementia because of a head injury or TBI is determined by a number of factors, including the severity of the injury, the area of the brain affected, and individual vulnerability.  

In people under the age of 50, head injury is the third most common cause of dementia, behind infection and alcoholism. Complications such as dementia are more common in older adults who have suffered a head injury. Children are more prone to experience more serious consequences. 

Traumatic brain injury is just one of several factors thought to increase the risk of dementia. There are some things we can’t change, like our age and heredity. To lower the risk of dementia, lifestyle factors such as smoking, high blood pressure, excessive alcohol consumption, and obesity can be addressed. 

Is there a specific type of dementia associated with head injuries or TBIs?

Chronic Traumatic Encephalopathy (CTE) is a kind of dementia strongly linked to repeated head traumas, notably in contact athletes or people with a history of persistent brain trauma. Degeneration occurs because of the death of nerve cells in the brain. CTE gets worse over time. CTE can only be diagnosed definitively after death, at a brain autopsy. Other types of dementia, such as Alzheimer’s disease, can, however, be caused by head injuries or TBIs. Harrison S. recognized this kind of dementia in professional boxers first. 

Multiple mild TBIs, as experienced by professional boxers, have been linked to an increased risk of chronic traumatic encephalopathy (CTE), a kind of dementia with specific clinical and histological hallmarks. Emerging evidence suggests that repeated mild traumatic brain injuries, such as those sustained in sports such as American football, boxing, hockey, and soccer, may be associated with an increased risk of traumatic encephalopathy syndrome or specific brain changes associated with chronic traumatic encephalopathy. 

CTE does not seem to be caused by a single head injury. It is linked to repeated head injuries, which are common in contact sports or military action. CTE has been linked to second impact syndrome, which occurs when a second head injury occurs before earlier head injury symptoms have completely gone. 

A study published by GeroScience demonstrated that brain changes in people with mild TBI and Alzheimer’s had similarities. The researchers found that there was a reduction in cortical thickness in both Alzheimer’s and TBI individuals when compared to healthy individuals. Cortical thinning is often associated with a reduction in memory, verbal fluency, and integrating new information and with a decreased ability to make decisions. 

Can the risk of dementia be reduced after a head injury or TBI?

It is not always feasible to completely remove the risk, taking the necessary precautions following a brain injury or TBI can help minimize the risk of developing dementia. This includes obtaining immediate medical assistance, adhering to suggested treatments and therapies, leading a healthy lifestyle, and safeguarding the brain from additional damage. 

You may have more difficulty recalling things from day to day after mild to severe TBI. There are very few strategies to restore the brain’s natural ability to learn and recall, according to research. After speaking with a doctor, one or two medications may be worth considering, but “brain training” programs and memory drills are ineffective. 

While many people recover completely from mild traumatic brain injuries, those who suffer from more severe TBIs often suffer from long-term consequences. This is because minor traumatic brain injuries generate less brain damage. As a result, there are more healthy brain cells to compensate for the loss of damaged ones. Furthermore, with a moderate TBI, there are fewer impaired functions to work on regaining. 

Brain injury healing is mostly dependent on encouraging healthy brain regions to make adaptive changes. When larger parts of the brain are injured, the possibility for neuroadaptive alterations to be stimulated is reduced.   

While brain damage after a traumatic brain injury is irreversible because injured brain cells cannot regenerate or repair themselves, functional recovery is possible. This is because healthy brain cells can reorganize and improve functions impaired by TBI. Because the effects of each TBI are distinct, it can be difficult to anticipate whether individuals will be able to recover completely. The repercussions of a traumatic brain injury can range from moderate to severe, depending on the level of brain damage. 

TBI can alter a person’s cognitive, physical, and emotional functions significantly. While brain injury cannot be reversed, TBI-affected functions can be regained because of the brain’s innate ability to rewire itself. Although TBI consequences might linger for years, people who have suffered a traumatic brain injury should not give up hope. Because the brain is incredibly adaptable, it is possible to regain significant function even years after injury. In the part that follows, we’ll go over methods to reduce persistent damage and enhance recovery after a TBI. 

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