COLUMBUS, Ohio -- New research has found that it's not just diet that influences cholesterol levels -- psychological stress and personality traits also play a role.

One study found that levels of LDL cholesterol (the so-called "bad" cholesterol) rose about 5 percent in a group of middle-aged airline pilots during a time of high occupational stress.

And in a second study, researchers discovered that medical students who scored high on a measure of conscientiousness had HDL (good) cholesterol levels about 4 percent higher than those who scored low on the measure.

The research was presented March 15 in Washington, D.C. at the International Congress of Behavioral Medicine, hosted by the Society of Behavioral Medicine.

These studies provide additional evidence of how negative psychological factors such as stress can be harmful to health and how positive traits -- such as conscientiousness -- may protecthealth, said Catherine Stoney, co-author of the studies and an associate professor of psychology at Ohio State University.

"Our research suggests that psychology and physiology work together in determining cholesterol levels," said Stoney, who is a member of Ohio State's new Institute for Behavioral Medicine Research.

"We're just beginning to understand the characteristics of individuals and situations that predict cholesterol levels."

High levels of LDL cholesterol have been shown to promote atherosclerosis, while HDL cholesterol may retard it.

In the stress study, 127 male and female airline pilots (average age 41) were given cholesterol tests shortly before and at a time when they were facing high occupational stress. The stress involved getting their pilots' licenses recertified. In addition, they performed stressful tasks in the laboratory while cholesterol levels were monitored.

The researchers tested the individuals for several factors that may influence cholesterol levels, including fat intake in their diets, waist-hip ratio, and perceived stress. Results showed that all of these factors had influences on levels of bad cholesterol for men, Stoney said. But stress -- both occupational and short-term -- influenced bad cholesterol levels independently of the other factors such as diet. When a subset of these men were tested again nearly a year later, similar findings emerged.

However, Stoney said, women in the study didn't show stress-related increases in bad cholesterol levels. She believes hormonal differences may explain why women didn't have the cholesterol increase seen in men.

Stoney said the finding that perceived stress had an independent effect on LDL cholesterol levels was particularly interesting.

"There are different ways that stressful situations can affect cholesterol levels. One way may be that people eat more high-fat foods when they're under stress, and that affects their cholesterol," she said. "But we found that perceived stress has an effect beyond diet."

In the personality study, the researchers gave 100 male and female medical students the NEO Five Factor Personality Inventory. This measure tests people on five personality traits: neuroticism, extraversion, openness to experience, agreeableness and conscientiousness.

The results showed that people who scored high on conscientiousness -- those who tend to be organized, reliable, hard-working, punctual and ambitious -- also had higher levels of the good cholesterol. Those who scored high on agreeableness -- those who were trusting, helpful, forgiving and altruistic -- were slightly more likely to have higher levels of good cholesterol, although this association wasn't as strong.

"We're not sure why conscientiousness is related to cholesterol levels," Stoney said. "But the results may help explain observations that have linked personality traits and longevity."

This study confirmed results from other research showing that women have higher levels of good cholesterol than do men.

Overall, the two studies indicate that stress and other psychological factors play an important role in cholesterol levels. "We need more research to find out how all of these factors relate to one another," she said.

Stoney conducted the research with Raymond Niaura, Linda Bausserman, Michael Goldstein, Mary Flynn and Peter Herbert. All except Stoney are from the Brown University School of Medicine.

Contact: Catherine Stoney, (614) 292-0588

Written by Jeff Grabmeier, (614) 292-8457

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