COLUMBUS, Ohio -- A new study has found that mild psychological stress can temporarily increase blood levels of a chemical associated with the development of heart disease.
The study of 34 middle-aged women found that brief periods of stress increased blood levels of the amino acid homocysteine. Research over the past 20 years has found that an even moderately elevated level of homocysteine is a risk factor for heart disease in both men and women.
"This is the first study to show that behavioral factors may influence homocysteine levels," said Catherine Stoney, author of the study and a professor of psychology at Ohio State University.
"We knew that psychological stress plays a role in cardiovascular disease. These findings suggests homocysteine may be one mechanism for the stress effect."
The study will be published May 14 in the journal Life Sciences. Homocysteine is a dietary byproduct of animal protein. Normally, it is broken down in the bloodstream by folic acid and the B vitamins. "People who have deficiencies in folic acid and the B vitamins have higher sustained levels of homocysteine and are at increased risk for cardiovascular disease," Stoney said.
This study involved 34 women between the ages of 40 and 63. Half were pre-menopausal and half were post-menopausal.
For the study, the participants came to Ohio State's General Clinical Research Center in the morning after an overnight fast. Researchers inserted a catheter into their arms to collect blood during the experiment.
During the experiment, the women were given two stress-inducing tests. In one test, they had to continuously and rapidly subtract 17s from a four-digit number. In the other test, the participants had to give a videotaped speech about an anger-provoking, hypothetical event. Blood samples were taken before, during and after the stress-causing tests.
Results showed that women experienced a sharp rise in homocysteine levels during the stress tests (from an average of 5.8 mol/l to an average of 6.2 mol/l). As expected, both heart rate and blood pressure also increased during stress.
"Even during the stressful period, the concentrations of homocysteine we saw were not at dangerous levels -- they were still in the normal range," Stoney said. "However, it was still significant that stress did have a measurable impact."
Researchers believe elevated levels of homocysteine is harmful because it causes damage to the cells lining the walls of arteries, Stoney said. This contributes to the development of plaque on the walls of the arteries.
The study compared pre- and post-menopausal women because there are differences between the two groups in both risk for cardiovascular disease and in physical responses to stress. The results did show one difference in postmenopausal women: their levels of follicle-stimulating hormone (FSH) were directly related to levels of homocysteine. This may be significant, Stoney said, because FSH levels increase in postmenopausal women, which may mean stress has a stronger effect on homocysteine levels in women after menopause.
Stoney said she now wants to see if stress has the same effect on homocysteine levels in men, and also determine how stress causes the increase in homocysteine.
The study was supported in part by the National Institutes of Health and Ohio State's General Clinical Research Center.