What Are the Causes of Brain Atrophy?

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Brain atrophy is shrinking of the brain caused by the loss of its cells, called neurons. Two types of brain atrophy can occur; generalized and focal. Generalized atrophy refers to neuron loss throughout the entire brain, and focal atrophy refers to neuron loss in a specific brain region. Symptoms of significant brain atrophy include progressive cognitive impairment involving multiple cognitive functions, otherwise known as dementia, seizures and aphasia, which is the disruption in the understanding or production of language or both. In some cases, brain atrophy can be normal and expected and is sometimes preventable. However, other causes are associated with disease progression or brain injury. Knowing the causes can empower people to do what they can to keep a healthy brain for as long as possible.

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Normal Aging

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Normal aging causes atrophy of the brain. The aging brain shrinks by an average of 1.9 percent every 10 years. It begins in young adulthood, but becomes more prominent when individuals reach their sixties. People can reportedly lose a half percent to 1 percent of brain volume per year after the age of 60. This is due to the number of cells in the brain decreasing with age, thus resulting in generalized atrophy. Some areas of the brain may shrink more than others, like the hippocampus, which is involved in memory.

However, overall cognitive functioning can remain unaffected as people age. The brain may become less efficient, but still be able to do the job. Research also shows that exercises for both the brain and body help to reduce brain atrophy.

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Disease, Stroke and Traumatic Brain Injury

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Several diseases can cause significant atrophy of the brain. Progressive neurodegenerative diseases of the brain, such as Alzheimer's disease, Huntington's disease, corticobasal degeneration, posterior cortical atrophy, multiple system atrophy and progressive supranuclear palsy, cause increased rates of brain atrophy. They initially cause focal atrophy of specific brain regions and then gradually progress to generalized atrophy involving the entire brain, which ultimately results in death.

Infectious diseases can also cause brain atrophy due to the pathogens attacking brain cells or due to the brain's inflammatory response to its presence. Stroke can cause brain atrophy by interrupting normal brain blood flow. The areas of the brain that do not receive blood begin to rapidly die, thus causing atrophy, potential cognitive deficits or death. Traumatic brain injury can work through the same mechanism as stroke by impeding blood while also causing direct tissue damage.

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Vitamin Deficiency

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A deficiency in vitamin B12 can result in significant atrophy of the brain. A study performed at the University of Oxford showed that healthy volunteers with low, but normal, levels of vitamin B12 had more brain volume loss than healthy volunteers with higher levels. This type of atrophy is preventable and often reversible if steps to improve B12 levels are implemented.

Excessive Alcohol Use

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A study performed by the John Hopkins Bloomberg Public School of Health showed that drinking alcohol is associated with a decline in brain volume. Specifically, it demonstrated that drinking more than 14 drinks per week results in significant brain shrinkage. The more people drink, the greater the volume loss per year. Gender appeared to interact with alcohol intake, because greater brain volume loss was found in women even though they tended to drink less per week than men.