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Brain MRI May Help Predict Alzheimer's

by Robert H. Shmerling, M.D.
Harvard Medical School

Parts of the brain's outer layer, the cortex, may become thinner before people develop symptoms of Alzheimer's disease, a new study suggests. Researchers were able to see the difference on a magnetic resonance imaging (MRI) scan. The study included 159 people. Their average age was 76. They were given MRIs as the study began. They also took tests of brain functions such as memory and problem solving. About 12% of the people showed thinning of the cortex. This was seen in areas that also become thinner in people with Alzheimer's disease. Most people had a cortex of average thickness. About 15% had a thicker cortex than average. People in these 3 groups did not differ in their results on brain function tests. But about 3 years later, 21% of the group with the thin cortex had lower scores on brain function tests. Only 6% of the average group and none of the group with the thicker cortex showed any decline. The journal Neurology published the study. HealthDay News wrote about it December 21.

What Is the Doctor's Reaction?

It's a major goal of researchers interested in diseases of the brain: figuring out who is at risk for Alzheimer's disease and other types of dementia.

Now researchers have found that how the brain looks on an MRI scan can reflect the risk of future memory trouble. They published their findings in the journal Neurology.

The study included 159 healthy older adults. Their average age was 76. All of them had magnetic resonance imaging (MRI) scans of their brains. Of these, 19 people (12%) had areas of the brain that appeared smaller than normal. The thinning was in 9 areas of brain cortex, the outer layers of the brain involved in higher brain function. These same areas are thinner in people with Alzheimer's disease. People in the study with thinned cortex were considered "high risk" for future problems with thinking and memory even though they had no current problems.

Researchers also defined an "average-risk" group. Their scans showed brain cortex with normal thickness. And there was a "low-risk" group whose brain cortex was larger than average.

People then had tests of brain function, such as memory and problem solving. There were also tests of attention and planning ability. During the next 3 years, some people had a decline in brain function. Researchers looked back at the original MRI scans. They noticed that the smaller the cortex in those key areas, the more likely people were to have decline.

• About 21% of those with a high-risk brain MRI had a decline in brain function.
• Only 7% of those at average risk and none of those in the low-risk group developed problems with brain function.
• Abnormal protein in the spinal fluid is linked with Alzheimer's disease. This protein was more common among those in the high-risk group (60%) than in the average-risk group (36%) or low-risk group (19%).

The MRI scan results didn't predict perfectly who would go on to develop a decline in brain function. But still, the trend was striking.

You might wonder why this matters. It's not as if you can control the size of your brain cortex. And it's not even clear that thinned brain cortex actually causes Alzheimer's disease. It's possible that whatever causes dementia also happens to cause shrinking in certain parts of the brain.

Still, this study is quite important. Here's why:

• Early diagnosis of Alzheimer's disease could lead to a better understanding of how dementia develops.
• Being able to identify people at increased risk of Alzheimer's disease could help in studies of treatment.
• MRI scanning could someday be accurate enough to screen for Alzheimer's disease. Those at high risk might make lifestyle changes and/or take medicines (when available) to prevent the disease.

We are a long way off from knowing how to use MRI scanning in the diagnosis or prevention of dementia. But this new study could be a step in that direction.

What Changes Can I Make Now?

Unfortunately, Alzheimer's disease can't be reliably prevented. Other types of dementia may be. For example, multi-infarct dementia is caused by multiple strokes. Several factors that increase the risk of stroke (such as high blood pressure) can be reversed or treated.

Many experts recommend the following to reduce the risk of Alzheimer's disease or other forms of dementia:

• Don't smoke.
• Exercise regularly. Previous research has found rates of Alzheimer's disease as much as 50% lower among those who are the most physically active.
• Keep your body mass index (BMI) in a healthy range. If your BMI is over 25 (and especially if it's over 30), try to lose excess weight. To do this, reduce the number of calories you eat and also get more exercise.
• Change your diet. Increase your intake of fruits, vegetables and omega-3 fatty acids. Decrease your intake of salt and saturated and trans fats.
• If you have diabetes or high cholesterol, work with your doctor to control them.
• Keep busy with work, hobbies and an active social life.
• "Exercise" your mind with activities that challenge your brain such as crossword puzzles or board games.

These measures are particularly important if you have a strong family history of dementia. And they may do more than lower your risk of developing dementia. Some of these measures may also lower your risk of developing diabetes or heart and artery disease. We don't have medicines that can prevent Alzheimer's disease. However, there are medicines approved to slow a person's decline with the disease.

Talk to your doctor about any factors that may increase your risk of dementia and what steps you can take to change them.

What Can I Expect Looking to the Future?

With the aging of our population, Alzheimer's disease and other types of dementia are expected to increase dramatically in the future. You can expect to hear about studies like this one that try to identify factors that increase the risk of dementia well before it develops.

I think we'll see new and better imaging tests. They are likely to be used along with blood, spinal fluid and genetic testing. That should set the stage for improving our understanding of dementia. And, more importantly, it should allow studies of potentially effective treatments.

Categories: Alzheimer's, Senior Health

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