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Connection Between Heart Disease and Alzheimer’s

By Dr. Crandall
Alzheimer’s now affects more than 5 million Americans, including one out of eight age 65 or older, and nearly half of those over the age of 85. In fact, someone in the United States develops the disease every 72 seconds.

Alzheimer’s kills nerve cells in the brain, making communication between the cells impossible. Eventually, it is fatal, but not before its victims spend years struggling with confusion, loss of memory, and eventually loss of personality.

There is a genetic connection between coronary heart disease and Alzheimer’s. In fact, Alzheimer’s disease and coronary heart disease share a common gene, called “APOE-4.”

The APOE-4 gene provides instructions for making a protein called apolipoprotein E, which combines with fats (lipids) in the body to form molecules called lipoproteins. Lipoproteins are responsible for packaging cholesterol and other fats and carrying them in the bloodstream.

Apolipoprotein E is also a major component of a specific type of lipoprotein called very low-density lipoproteins (VLDLs), which influence the composition of cholesterol. While most cases of Alzheimer’s disease are not directly inherited, people who do have the APOE-4 gene are at higher risk for both heart disease and Alzheimer’s. It is a fascinating connection.

One of the reasons Alzheimer’s disease is so terrifying is that scientists have yet to pinpoint exactly why some people get the disease and others do not. Yet as they delve deeper into the causes of both heart disease and Alzheimer’s, researchers are turning up evidence of common symptoms.

For instance, two decades ago a Kentucky medical examiner noted that the brains of people who had died from heart disease were more likely to have “plaques and tangles” characteristic of Alzheimer’s disease. (“Plaques” refer to abnormal clumps of amyloid protein that occur between nerve cells; “tangles” are an accumulation of a different protein, called tau protein, inside of nerve cells.)

But why is this so? One of the major suspects appears to be atherosclerosis (hardening of the arteries), the disease process that causes coronary artery disease. Atherosclerosis is the buildup of the fatty plaque, which narrows the heart’s coronary arteries, impeding its ability to pump blood to the rest of the body, including the brain.

And the brain is a glutton for blood; in fact, it uses 20 to 25 percent of the blood the heart pumps. Therefore, any reduction in blood flow damages the brain, and can pave the way for Alzheimer’s disease. Studies have found that this shortage of oxygen activates a gene that is responsible for producing the harmful amyloid-beta plaques found in the brains of Alzheimer’s patients. This process sets off a cascade of chemicals that kill brain cells and cause Alzheimer’s disease.

Because of this process, scientists are increasingly viewing Alzheimer’s as a vascular disease, similar to coronary artery disease or stroke.
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