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Study Suggests Why Heart Attack Victims Do Better with Social Support E-mail
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Researchers have identified specific damages to the brain that may occur when heart attack victims are socially isolated from others. The study in mice found that those animals that lived alone before undergoing a heart attack showed five to eight times more damage to neurons in one part of the brain than did similar animals that lived with others.

The study in mice found that those animals that lived alone before undergoing a heart attack showed five to eight times more damage to neurons in one part of the brain than did similar animals that lived with others.

While studies in humans have shown that socially isolated heart attack victims have a lower survival rate than others, this study may help reveal the mechanisms behind that result, said Zachary Weil, co-author of the study and former doctoral student in neuroscience at Ohio State University.

"This study shows that there are basic changes that occur in the brain when a heart attack victim is socially isolated," Weil said.

"In these mice, living with others seemed to provide strong protection from some of the damaging results of a heart attack."

The study appears in the October 2008 issue of the journal Molecular Psychiatry.

In the study, mice were put into two groups - members of one group lived alone, while the others lived communally in a cage with four other mice.

After two weeks with these living arrangements, some of the mice underwent a surgically induced heart attack. Those in a control group underwent the same surgical procedure, but the researchers prevented any loss of oxygen to the brain that would occur in a typical heart attack.

Brain tissue and blood samples were later collected from the mice. Researchers compared damage in the hippocampus, the area of the brain that plays a key role in memory. A lack of oxygen during a severe heart attack - one where the victim stops breathing - can either kill or seriously damage neurons, the primary cells of the nervous system.

Results showed that the mice that were socially isolated prior to the heart attack showed five to eight times more damage to their neurons compared to mice that were housed together, said Weil, who is now a post-doctoral researcher at Rockefeller University in New York.

Socially isolated mice also showed evidence of greater inflammation in the hippocampus, when compared to socially housed and control mice.

"There was a runaway inflammatory response in the tissue of socially isolated mice, which is damaging to the brain," said Randy Nelson, a co-author of the study and professor of psychology and neuroscience at Ohio State.

Socially isolated mice showed increased activation of microglia, a type of immune cell in the central nervous system that responds to damaged neurons, the study found.

One of the ways microglia respond is by releasing tumor necrosis factor alpha (TNF-α), one of a large family of proteins called cytokines -- chemical messengers that are mobilized when the body is injured or has an infection. These cytokines cause inflammation in their effort to repair an injured or infected area of the body.

Levels of TNF-α were elevated in isolated mice, but not in socially housed mice, compared to the control mice.

The higher levels of TNF-α in the socially isolated mice, and the inflammation it caused, was the main reason for the increased neuronal damage in these animals, Nelson said.

"Inflammation is normally good, but in this case it is too much of a good thing," he said.

In addition, results showed that the isolated mice had higher levels of the stress hormone corticosterone following the heart attack. Other studies have linked elevated levels of this hormone to increased neuronal damage.

"We found that the hormonal stress response network is more activated after cardiac arrest in socially isolated animals," said Courtney DeVries, in whose lab the work was conducted and another co-author and associate professor of psychology and neuroscience at Ohio State.

"This is contributing to damage in the neurons."

DeVries said this study, and others in her lab and in labs across the country, have highlighted the importance of social isolation and relationships in health, and specifically in recovery from heart attacks and strokes.

In fact, studies have shown that social isolation is as strong a predictor of one-year survival rates among heart attack victims as more classic risk factors such as high cholesterol and hypertension.

"One of the stumbling blocks has been that we haven't found the mechanism that explains why socially isolated individuals don't fare was well when it comes to heart attacks.

"But this study shows there is a physical reason why isolated people don't do as well, and it has to do with the inflammatory response to a heart attack."

If these findings continue to be replicated, it may suggest new ways to help treat heart attack victims.

"It is very difficult to alter people's social networks, but if we can understand the exact mechanism behind why socially isolated people don't fare as well after a heart attack, we may be able to develop therapies that can improve their outcomes," DeVries said.

Other co-authors on the study, all from Ohio State, were Greg Norman, Jacqueline Barker and Alan Su. The work is part of ongoing studies at Ohio State's Institute for Behavioral Medicine Research.

About Cardiovascular disease

Cardiovascular disease is a broad term that includes several more specific cardiovascular conditions. Cardiovascular disease is the leading killer in the US. 

Common heart conditions include: 

  • Arrhythmias. Irregular, or abnormally fast or slow, beating of the heart. The heart beat is controlled by electrical impulses. When the timing or frequency of these electrical impulses are disrupted, arrhythmias develop. Some arrhythmias are quite serious. An example is ventricular fibrillation, a severely abnormal heart rhythm that causes death unless treated right away by providing an electrical shock to the heart (called defibrillation). Others are less severe but can develop into more serious conditions over time. A particular concern is atrial fibrillation. Atrial fibrillation is rapid, irregular beating of the upper chambers of the heart. The chambers can quiver instead of beating in a regular pattern. Blood is not fully pumped out of them and may pool and clot.
  • Cardiomyopathy. A weakening of the heart muscle or a change in heart muscle structure. It often results in inadequate heart pumping or other heart function abnormalities. These can result from various causes, including prior heart attacks, viral or bacterial infections, and others.
  • Congenital Heart Disease. Malformations of heart structures, present during pregnancy or at birth. These may be caused by genetic factors or by adverse exposures during pregnancy. Examples include holes in the walls that divide the heart chambers, abnormal heart valves, and others. Congenital heart defects can disrupt the normal flow of blood through the heart. Congenital heart defects are the most common type of major birth defect.
  • Coronary Heart Disease (CHD). CHD is the most common type of heart disease. CHD occurs when the coronary arteries, that supply blood to the heart muscle, become hardened and narrowed due to the plaque buildup. The plaque buildup and the narrowing and hardening of the arteries is called atherosclerosis. Plaques are a mixture of fatty substances including cholesterol and other lipids. Blood flow and oxygen supply to the heart can be reduced or even fully blocked with a growing plaque. Plaques may also rupture and cause blood clots that block arteries. CHD can lead to a heart attack. Angina, the most common symptom of CHD can also occur. Angina is chest pain or discomfort that occurs when the heart muscle is not getting enough blood. Irregular heart beats, called arrhythmias, can develop.Over time, CHD can weaken the heart muscle and lead to heart failure, a serious problem where the heart cannot pump blood the way that it should.
  • Heart Attack. A heart attack , also called a myocardial infarction may occur when blood supply to the heart is severely reduced or completely blocked. When blood flow is restricted the heart muscle cells do not receive enough oxygen and begin to die. The more time that passes without treatment to restore blood flow, the greater the damage to the heart. This damage can cause irregular heart rhythms or even sudden cardiac arrest or stopping of the heart beat. Death can result. Coronary artery disease is the chief underlying cause of a heart attack. A less common cause of a heart attack is a severe spasm of a coronary artery that reduces the blood supply to the heart.
  • Heart Failure. This may also be called congestive heart failure or chronic heart failure. Heart failure is a condition where the heart cannot pump enough blood and oxygen to meet the needs of other body organs. Heart failure does not mean that the heart has stopped, but that it cannot pump blood the way that it should. Heart failure is a serious condition. There is no cure for heart failure at this time, except a heart transplant. Once diagnosed, medicines are needed for the rest of the person's life.
  • Peripheral Arterial Disease (PAD). Hardening of the arteries that supply blood to the arms and legs. PAD is usually the result of atherosclerosis, the buildup of plaque and narrowing of the arteries. Blood flow and oxygen to the muscles in the arms and legs can be reduced or even fully blocked. Painful leg muscles, numbness, swelling in the ankles and feet, and weak pulse in the feet are some of the signs and symptoms of PAD.
  • Rheumatic Heart Disease.This condition is damage to the heart valves and other heart structures due to inflammation and scarring caused by rheumatic fever, which occurs from streptococcal infection.Heart disease is an umbrella term for a number of different diseases affecting the heart.Heart disease is a number of abnormal conditions affecting the heart and the blood vessels in the heart.

 

 
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