The high-pressure deadlines at work boost a man's chances of having a heart attack within the next 24 hours by a factor of six, Swedish researchers say.

Short-term bursts of stress at work seem to have a more harmful effect on the heart than stress that accumulates over 12 months, according to scientists who studied 3,500 people.

In the study, researchers monitored the number of first heart attacks in healthy people aged 45 and 70, from 1992 to 1994.

Swedish researchers say the high demands of work have the potential to trigger heart attacks.

Changes in the workforce, such as increases in competition and workload, and less job security, motivated the researchers to explore work as a potentially harmful source of stress.

The team aimed to test whether a short-term period of stress acted as a trigger mechanism for heart attacks, compared to stress that accumulates over time.

Dr. Jette Moller of the department of public health sciences at Stockholm's Karolinska Institute and her colleagues used surveys, interviews and health exams, and took into account other known risk factors such as smoking and high blood pressure.

The results suggest women were three times as likely, and men six times as likely to have a heart attack if they had taken on more responsibilities at work, particularly if these were viewed negatively.

For women, a change in financial circumstances tripled their risk, the researchers found.

Annual risk

Looking at the estimated increase in risk on an annual basis illustrates the potential public health implications of the findings, the team writes in the January 2005 issue of the Journal of Epidemiology and Health.

For example, a 55- to 70-year-old-man in the Stockholm area had a 0.464 per cent yearly risk of heart attack in the study, the researchers wrote.

If he worked eight hours per day, five days a week and experienced pressing deadlines once a week, his yearly risk would increase to 0.564 per cent, giving an annual risk ratio of 1.215, or 20 per cent excess risk.

They note that since this is the first study to show such a work link, the findings need to be confirmed by other research.

The authors suggest the result is biologically plausible, given what is known about how heart attacks are triggered.