The Medical Post, February 7, 1995, p. 46
SANTA BARBARA - Job strain may play a causal role in the development of high blood pressure and subsequent cardiovascular events such as stroke and heart attack.
Researchers at Cornell University Medical Center in New York, N.Y., have been investigating the concept of job strain and how it relates to ambulatory blood pressure. They define job strain as a job with high workload demands and low control or "decision latitude." This type of strain, they say, may provide a clue to the cause of what is essentially a 20th century problem: hypertension.
Dr. Peter Schnall, director of the Center for Social Epidemiology, and associate clinical professor at the University of California, Irvine, reported at the meeting here findings from the ongoing Cornell Worksite Study involving about 300 men and women from eight worksites in New York City.
To date, results have only been reported for men in the study, as women were not initially included. "We have 130 women in the second wave of the study, but we have only cross-sectional results so far," Dr. Schnall said. They are currently preparing these results for publication, he added, but "they're very different from the results we're getting from men."
Initial study findings had shown job strain among males was a risk factor for hypertension: those who reported having job strain were three to five times more likely to have hypertension than those who did not report such strain. They also found it was related closely to ambulatory blood pressure and was associated with increases in left ventricular mass index.
The researchers differentiate job strain from job stress. "when we look at the psychological characteristics that people have when they say they have high demand and low control, they are not telling us they're angry or anxious or feel stressed. "They tell us they don't like their jobs, but there's little impact of job strain on psychological variables like demoralization, depression, anxiety and anger."
Now, results of a prospective follow-up of almost 200 men over three years has shown those who reported job strain both at baseline and three years later had increases in both their systolic and diastolic blood pressures. Men who reported no job strain during the first wave had no net increase in their blood pressure over the three years, Dr. Schnall said. Using this group as a reference point, they found men who reported job strain at both points had increases in systolic blood pressure of an average 6.1 mmHg, and in diastolic pressure of 4 mmHg.
The findings among groups who crossed over, that is, who reported job strain at the first measure and not the second, or vice versa, supported the hypothesis. Those who went from strain to no strain had decreases, and those who went from no strain to strain had increases in their ambulatory blood pressures of about 2 mmHg systolic and 1-1.5 mmHg diastolic.
"I think the cross-over effects are almost a convincing about the role that job strain is playing as what happens to those who are exposed chronically over both periods," he said.
They also found if subjects reported low co-worker support was an inverse relationship at both points, there between that lack of support pressure after controlling for all other risk factors. Both and ambulatory blood job strain and low co-worker support added up to an 8 mmHg increase in systolic and almost 7 mmHg diastolic blood pressure over three years. "Our that job strain is a risk factor for research group believes hypertension, that it's we need an intervention study before we can make that a playing a causal role, but definitive statement."
These studies could take advantage of natural experiments now going on in the corporate community as companies downsize, create new kinds of jobs, or modify their work environments after innovative Japanese or Scandinavian models. "The psychosocial work environment in America is changing every day," he said. The other approach would be to find companies interested in participating in such an experiment, manipulating dimensions such as social support, demands and control among their employees.
"If changing job strain results in lowered blood pressure, we may also have a huge impact on both stroke and coronary heart disease down the road," Dr. Schnall said.
"What we need to do is create work which is respectful for people," he concluded. "If it's respectful work, work people feel good about, where they have some control over the work process, where they work with their colleagues in a positive way, those are also characteristics of low strain work."