Men who bottle up their anger at being unfairly treated at work are up to five times more likely to suffer a heart attack, or even die from one, than those who let their frustration show, a Swedish study has found.

The study by the Stress Research Institute of Stockholm University followed 2,755 employed men who had not suffered any heart attacks from 1992 to 2003.

At the end of the study, 47 participants had either suffered an attack, or died from heart disease, and many of those had been found to be "covertly coping" with unfair treatment at work.

"After adjustment for age, socioeconomic factors, risk behaviors, job strain and biological risk factors at baseline, there was a close-response relationship between covert coping and the risk of incident myocardial infarction or cardiac death," the study's authors wrote.

Covert coping was listed as "letting thing pass without saying anything" and "going away" despite feelings of being hard done by colleagues or bosses.

Men who often used these coping techniques had a two to fivefold higher risk of developing heart disease than those who were more confrontational at work, the study showed.

The researchers said they could not answer the question of what might be a particularly healthy coping strategy at work, but listed open coping behavior when experiencing unfair treatment or facing a conflict as "protesting directly," "talking to the person right away," "yelling at the person right away" or "speaking to the person later when things have calmed down."

The study was published in the Journal of Epidemiology and Community Health.

(Read by Lee Hannon. Lee Hannon is a multimedia journalist at the China Daily Web site.)