News Review From Harvard Medical School -- Blood-Vessel Damage Studied in Alzheimer's
Damage to small blood vessels in the brain may play a role in causing Alzheimer's disease, a small study suggests. The study included 20 people who had been diagnosed with Alzheimer's and 21 who did not have it. It also included 59 people who had mild cognitive impairment. People with this milder memory problem have an increased risk of Alzheimer's disease. Researchers looked at information from brain scans. In some people, the scans showed amyloid plaque deposits in the brain. This has long been considered a sign of Alzheimer's disease. Some people also had areas of intense white matter in the brain. These areas indicate damage in small blood vessels. People with amyloid deposits who had been diagnosed with Alzheimer's had larger areas of intense white matter than normal subjects. This combination of amyloid and intense white matter also was found in some people with mild cognitive impairment. This group was more likely than others with the condition to develop Alzheimer's disease during nearly 3 years of follow-up. The journal JAMA Neurology published the study online. HealthDay News wrote about it February 18.
By Howard LeWine, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
Alzheimer's disease continues to be more difficult to understand that we hoped. Alzheimer's disease is the most common type of dementia. The risk of developing it increases with age. As people live longer than ever, the numbers of those affected will increase dramatically during the next couple of decades.
Despite years and millions of dollars spent on research, doctors still diagnose the disease in the same way. They look at the symptoms and how they come about over time. There is no specific test, such as an MRI or PET scan, that can confirm an Alzheimer's diagnosis.
The main features of Alzheimer's disease are impaired memory and thinking. The symptoms come on gradually and get worse over time. At an early stage, it's not possible to determine if this is just a bit of age-related change. Another possibility is what doctors call mild cognitive impairment. People with this condition have some short-term memory loss with minimal thinking problems. Will it stay the same? Or will it get worse and turn into dementia?
What we can see inside the brain does not make a diagnosis any clearer. The classic protein deposits seen in the brains of people with Alzheimer's disease are called amyloid. But amyloid deposits are found in up to 30% of elderly people with normal memory and thinking.
There must be something else happening in people with Alzheimer's, other than just the buildup of amyloid in the brain. It could be injury to the smallest blood vessels that feed oxygen and nutrients to the brain. That's the possibility raised by researchers in a new study. They reported their findings online yesterday in the journal JAMA Neurology.
The researchers used PET scans to determine the amount of amyloid deposits and the number of intense spots in brain white matter. Researchers compared PET scans in normal older adults, those with Alzheimer's disease and those with mild cognitive impairment.
They found that the amount of amyloid was only somewhat different in the three groups. The difference was not enough to make one diagnosis or another. What made a greater difference was the amount of high-intensity white matter. High-intensity spots indicate small vessel damage. Greater amounts of small-vessel damage, combined with amyloid deposits, provided a more consistent picture of Alzheimer's disease. The combination also predicted which patients with mild cognitive impairment were more likely to develop Alzheimer's dementia.
What Changes Can I Make Now?
Today, we don't know how you can alter the amount of amyloid deposits that will occur in your brain. Some people inherit a much greater chance of having this happen starting at a relatively young age.
But we can decrease our risk of developing damage to the small blood vessels in the brain. The advice is similar to what you can do to reduce your risk of heart attack and stroke:
- Stay physically active, and dedicate time every day to exercise. Ideally, aim for 45 to 60 minutes of exercise most days of the week. But any and all physical activity helps to reduce risk.
- Maintain a healthy weight, which also helps lower your risk of developing type 2 diabetes.
- Don't smoke.
- Eat plenty of fruits and vegetables. Choose healthier protein sources, such as fish, beans and soy products.
- Keep your blood pressure in the normal range.
- If necessary, lower your LDL cholesterol through diet and drugs.
What Can I Expect Looking to the Future?
This was a very small study, but one with intriguing results. We will need much larger studies to verify a connection between amyloid deposits and small-vessel damage. Meanwhile, we do know from other studies that people who lead healthier lifestyles have less chance of developing Alzheimer's disease. Get started now to help protect your brain, as well as your heart.