Mild cognitive impairment (MCI)

Brain shrinkage in MCI and Alzheimer's disease Enlarge image

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Brain shrinkage in MCI and Alzheimer's disease

Brain shrinkage in MCI and Alzheimer's disease

Dementia causes the brain to lose mass, especially in critical areas. Note the difference in size between a healthy brain (top), a mild cognitive impairment brain (middle) and an Alzheimer's disease brain (bottom).

There's no single cause of mild cognitive impairment. In some people, mild cognitive impairment is due to Alzheimer's disease. But there's no single outcome. Symptoms may remain stable for years or they may improve over time. Or mild cognitive impairment may progress to Alzheimer's disease dementia or another type of dementia.

Mild cognitive impairment, also known as MCI, often involves the same types of brain changes seen in Alzheimer's disease or other dementias. But in MCI, the changes occur at a lesser degree. Some of these changes have been seen in autopsy studies of people with mild cognitive impairment.

These changes include:

• Clumps of beta-amyloid protein, called plaques, and neurofibrillary tangles of tau proteins that are seen in Alzheimer's disease.
• Microscopic clumps of a protein called Lewy bodies. These clumps are related to Parkinson's disease, dementia with Lewy bodies and, sometimes, Alzheimer's disease.
• Small strokes or less blood flow through brain blood vessels.

Brain-imaging studies show that the following changes may be related to MCI:

• Decreased size of the hippocampus, an area of the brain important for memory.
• Larger size of the brain's fluid-filled spaces, known as ventricles.
• Reduced use of glucose in key brain areas. Glucose is the sugar that is the main source of energy for cells.

Risk factors

The strongest risk factors for mild cognitive impairment are:

• Older age.
• Having a form of a gene known as APOE e4. This gene also is linked to Alzheimer's disease. But having the gene doesn't guarantee a decline in thinking and memory.

Other medical conditions and lifestyle factors have been linked to a higher risk of changes in thinking, including:

• Diabetes.
• Smoking.
• High blood pressure.
• High cholesterol, especially high levels of low-density lipoprotein, known as LDL.
• Obesity.
• Depression.
• Obstructive sleep apnea.
• Hearing loss and vision loss that are not treated.
• Traumatic brain injury.
• Lack of physical exercise.
• Low education level.
• Lack of mentally or socially stimulating activities.
• Exposure to air pollution.

Complications

Complications of mild cognitive impairment include a higher risk — but not a certainty — of dementia. Overall, about 1% to 3% of older adults develop dementia every year. Studies suggest that around 10% to 15% of people with mild cognitive impairment go on to develop dementia each year.

Prevention

Mild cognitive impairment can't be prevented. But research has found that some lifestyle factors may lower the risk of getting it. These steps may offer some protection:

• Don't drink large amounts of alcohol.
• Limit exposure to air pollution.
• Reduce your risk of a head injury, such as by wearing a helmet when riding a motorcycle or bicycle.
• Don't smoke.
• Manage health conditions such as diabetes, high blood pressure, obesity and depression.
• Watch your levels of low-density lipoprotein (LDL) cholesterol and get treatment if the levels are high.
• Practice good sleep habits and manage any sleep conditions.
• Eat a healthy diet full of nutrients. Include fruits and vegetables and foods low in saturated fats.
• Stay social with friends and family.
• Get moderate to vigorous exercise most days of the week.
• Wear a hearing aid if you have hearing loss.
• Get regular eye exams and treat any vision changes.
• Stimulate your mind with puzzles, games and memory training.