Age and gender play a major role in how people respond to stress, according to a new study on 20-to-64-year-olds. Published in the journal Psychophysiology, the investigation was led by scientists from the Université de Montréal and the Montreal Heart Institute in collaboration withcolleagues from the Université du Québec à Montréal and McGill University.

"Our findings suggest that women who are more defensive are at increased cardiovascular risk, whereas low defensiveness appears to damage the health of older men," says Bianca D'Antono, a professor at the Université de Montréal Department of Psychiatry and a Montreal Heart Institute researcher.

Defensiveness is a trait characterized by avoidance, denial or repression of information perceived as threatening. In women, a strong defensive reaction to judgment from others or a threat to self-esteem will result in high blood pressure and heart rate. Contrarily, older men with low defensive reactions have a higher cardiovascular rates.

The study was conducted on 81 healthy working men and 118 women. According to Dr. Jean-Claude Tardif a Université de Montréal professor and Montreal Heart Institute researcher, the physiological response to stress in women and older men is linked to this desire of maintaining self-esteem and securing social bonds.

"The sense of belonging is a basic human need," says D'Antono. "Our findings suggest that socialization is innate and that belonging to a group contributed to the survival of our ancestors. Today, it is possible that most people view social exclusion as a threat to their existence. A strong defensive reaction is useful to maintain one's self-esteem faced with this potential threat."

As part of the experiment, participants completed four tasks of varying stress levels. The first task involved reading a neutral text on Antarctica's geography before a person of the same sex. The second and third tasks involved role-playing in which participants followed a script where they were sometimes agreeable and sometimes aggressive. The final task involved a non-scripted debate on abortion.

Heart rate and blood pressure were measured during each of these tasks as was the level of cortisol in saliva. Results showed that women and older men had elevated cardiovascular, autonomic and endocrine responses to stress -- all potentially damaging to their health. The research team cautions, however, that more studies are needed to evaluate the long-term effects of defensiveness and its association to stress response patterns in disease development.

This study was supported by the Canadian Institutes of Health Research and the Fonds de la recherche en santé du Québec.

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