A new study has identified one possible reason that people who show high levels of hostility and anger are more likely to develop heart disease. Researchers at Ohio State University found that men and women with higher levels of hostility also showed higher levels of homocysteine -- a blood chemical strongly associated with coronary heart disease (CHD).
Men who reported that they consistently held in angry feelings also showed higher levels of homocysteine. "Many studies have shown hostility and anger expression to be potent risk factors for coronary heart disease, but this study is the first to suggest this potential explanation for why they are linked to CHD," said Catherine Stoney, co-author of the study and associate professor of psychology at Ohio State.
This study is also one of the first to examine how psychological and behavioral factors are related to homocysteine.
Stoney conducted the study with Tilmer Engebretson, an adjunct assistant professor at Ohio State. The results was published in the April 28 issue of the journal Life Sciences.
The study involved 33 women and 31 men, all healthy and none taking any medications. After arriving at Ohio State's General Clinical Research Center, they completed questionnaires measuring hostility and anger expression. The researchers then drew blood samples and measured homocysteine concentrations.
Homocysteine is a dietary byproduct of animal protein. Normally, it is broken down in the bloodstream by folic acid and the B vitamins. Researchers believe elevated levels of homocysteine causes damage to the cells lining the walls of arteries, which contributes to the development of plaque.
In both men and women, this study showed that higher levels of hostility were associated with higher levels of homocysteine. "These were healthy people with no known cardiovascular disease or major risk factors, so the levels of homocysteine were still in the normal range even for those with higher levels of hostility," Stoney said. "We would expect that in people with heart disease, both hostility and homocysteine levels will be far higher than what we found. The fact that we found this relationship even among healthy people is significant."
This study, like others, found that men had higher levels of homocysteine than did women, Stoney said. However, once researchers took into account the fact that men showed higher levels of hostility and inhibition of anger than did women, the gender difference in homocysteine nearly disappeared. "This shows that the gender differences we see in homocysteine levels may be partly reflecting gender differences in hostility and anger expression," Stoney said. "Because men show more hostility than women, they have higher levels of homocysteine and are at greater risk for heart disease."
Moreover, the fact that inhibition of anger was associated with higher homocysteine levels only in men may be because men are more likely than women to hold in anger, she explained.
In a previous study, Stoney found that psychological stress can temporarily increase homocysteine levels. Because people high in hostility are known to report more life stress, she said it is possible that homocysteine concentrations are elevated among these individuals due to increased stress. "We know from our work and that of others that people who are hostile have a chronically "turned-on" sympathetic nervous system," she said. "They have higher blood pressure, higher heart rates and higher cholesterol among other things.
"One potential picture emerging from the current data is that men, particularly high-hostile men, have a sympathetic nervous system that is always turned on, resulting in higher homocysteine levels." Stoney said one of the next goals of her research is to look more closely at how hostility and anger cause elevated levels of homocysteine.
This study was funded by the National Institutes of Health, National Heart, Lung and Blood Institute and by the Ohio State General Clinical Research Center.