Engaging in stressful tasks like trying to meet a deadline may strengthen the immune system while exposure to stress that must be endured passively - like watching violence on TV - may weaken it, a researcher at the Ohio State University says. The conclusion is based on a study that was designed to draw out the different effects that active and passive coping might have on the body's defenses. It presents some of the strongest evidence yet that certain kinds of stress can promote good health.
"Our findings lend scientific truth to the idea that a hassle a day keeps the doctor away," said Jos A. Bosch, postdoctoral fellow in oral biology at Ohio State and lead author of the study. The work was published in the current (September-October 2001) issue of the journal Psychophysiology. Bosch did the research in collaboration with scientists at the University of Amsterdam, Vrije University in The Netherlands and the Academic Center for Dentistry Amsterdam.
Bosch and his colleagues conducted their experiments on a group of 34 volunteers, all of whom were male undergraduate students. The subjects were exposed to two different stressful experiences. The first was a timed memory task that required the students to memorize some given material and take a subsequent 12-minute test. In the second activity, the subjects were shown a gruesome 12-minute video on surgical procedures.
The difference between the two kinds of stresses - both of which are considered acute, rather than chronic, stress - was that participants were actively engaged in the memory task whereas the video had to be watched passively.
To examine the effect of these stresses on the immune system, the researchers studied the concentration of certain defense proteins in the saliva of the subjects. These proteins - known as immunoglobulins - are also contained in body fluids that make up the protective outer film of organs such as the lungs. The deployment of these immune factors inside the human body constitutes what biologists call the secretory immune system - the first line of defense that pathogens have to cross before invading tissues.
Bosch and his colleagues found that the memory task caused an increase in the salivary concentration of a major immune factor - the SIgA or secretory immunuglobulin A. The video had the opposite effect, lowering SIgA levels in the saliva.
"It appears that the stress from engaging in the memory task activated the subjects' immune system, whereas the stress from watching the video caused a downregulation (or weakening) of immunity," Bosch said.
The results suggest that deadlines and challenges at work could be a good thing. "Even being annoyed about something, particularly if it is for a short time, could help strengthen the body's defenses," Bosch said.
Being exposed to violent scenes on television, on the other hand, may suppress the immune system. The continuous replays of the World Trade Center towers' collapse on September 11, Bosch said, were a likely example.
While analyzing saliva samples, the researchers also measured the concentration of a molecule that is responsible for transporting immunoglobulins from their site of production to the saliva. Defense proteins bind to this molecule - called secretory component (SC) - and are carried by it into the protective fluids of the secretory immune system.
SC concentration increased during both the memory task and the video viewing. For the memory task, the researchers could not conclude if the increased availability of SIgA was a result of higher production of the immune factor or the result of increased flow of SIgA into the saliva.
"The greater abundance of transporting molecules means there could be higher amounts of SIgA in the saliva just from increased transportation activity, even without an actual increase in the production of immunoglobulin," Bosch said.
During the video, however, there was a dip in salivary immunoglobulin inspite of increased SC concentration. This indicated that exposure to the video suppressed the production of defense proteins by immune cells.
As a next step, Bosch intends to investigate the mechanisms underlying the immunological effects of active and passive coping.
