According to a new study, short periods of psychological stress can cause the body to take longer to clear heart-damaging fats from the bloodstream. Ohio State University researchers tested how quickly triglycerides - a type of fat that has been linked to heart disease - cleared out of the bloodstream of volunteers during a stress-inducing test. They compared the results to a session in which the volunteers rested. They found that in all cases, stress caused triglycerides to stay in the bloodstream longer.
Catherine Stoney, co-author of the study, says that the findings suggest one reason stress has been linked to heart disease. "If a person has a high-fat snack or meal during a time of stress, that fat is going to be circulating in the blood for a longer period of time," said Stoney, a professor of psychology at Ohio State University. "That means it may be more likely to be deposited in the arteries where it can contribute to heart disease," said Stoney.
Details of the study are published in the current issue of the journal Psychophysiology. Seventy healthy, nonsmoking middle-aged volunteers -- half men and half women -- took part in the study. Half of them were between the ages of 40 and 48 and half were between 54 and 61. The two age groups let the researchers consider both premenopausal and postmenopausal women during the project.
The volunteers were tested twice within three days. During both sessions, an intravenous tube was inserted into the veins of the volunteers. A solution containing triglycerides - the equivalent of about 100 calories - was then intravenously administered. The procedure replicated what would happen in a person's bloodstream hours after they ate a meal containing fat, Stoney said.
During one session, the volunteers rested and their triglyceride level was checked continuously for 40 minutes. In the other session, the volunteers were administered the triglyceride solution and then given 40 minutes of stressful tests. The tests included having to prepare and give a videotaped speech, a difficult word problem task, a psychomotor task consisting of drawing mirror images, and a task where they had to quickly and accurately subtract two digit numbers from four-digit numbers. Their triglyceride level was monitoring continuously for 40 minutes.
In all 70 volunteers, triglyceride levels declined faster in the restful session than in the session where they completed the stressful tests, Stoney said. Triglyceride levels declined overall an average of 2.8 percent a minute in the stress-inducing test session, compared to a quicker 3.2 percent per minute in the resting session.
For some people, the difference between the stressful and restful sessions was quite dramatic, Stoney said, while in others the differences in triglyceride levels were small. This reflects individual differences in how people metabolize fat. However, it was significant that stress had negative effects in all the volunteers, she said. "During stress, people are not metabolizing fat as rapidly and efficiently," Stoney said.
During the non-stress session, women cleared triglycerides out of their bloodstreams more quickly than men did. These findings were consistent with other research, Stoney said, but the research found no difference in how quickly men and women cleared triglycerides during stress.
Because reproductive hormones might affect how triglycerides are cleared, the researchers separated pre- and naturally postmenopausal women. They found no differences in how these groups responded, however. In an additional analysis, the researchers also compared postmenopausal women who were taking hormone replacement therapy with those who were not. Again, they found no differences.
Source: Ohio State University
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