Over three years, the scientists used ultrasound imaging to measure any thickening of the carotid arteries, which carry blood to the brain. Thickening of these arteries in the neck can signal a buildup of artery-clogging plaque deposits in other large vessels, including ones in the heart. Stress can raise clotting factors in the blood and may prompt the release of fat into the bloodstream, which can lead to clogging of the arteries. Physical activity, on the other hand, has been shown to reduce levels of these fatty acids. Researchers found, to their surprise, that people who got the most physical activity on the job had the greatest thickening of the arteries, Nordstrom said.
Conventional wisdom is that being active improves cardiovascular health.
And a separate part of the study supported the conventional wisdom. The scientists went back to a stress questionnaire they had done earlier on the same people. The questionnaire asked people about such things as whether there had been a marked increase in their workload, and whether they had trouble sleeping because their jobs were still on their minds. The researchers found that the people who worked the hardest, and who worked the most hours, reported the greatest job stress, Nordstrom said. And when the researchers did statistical analysis, it turned out that the job stress was most closely associated with the increase in carotid thickening, she said.