Long hours at work double your chances of a second heart attack - study

If you've been unlucky enough to suffer a heart attack, perhaps take it as a sign to cut back on work.

A new study has found people who work long hours are far more likely to suffer a second attack.

"Looking at long working hours and job stressors was helpful in determining how hostile a working environment was and how much potential stress a participant could be under," said lead author Xavier Trudel of Canada's Université Laval.

"Once both factors are introduced, there’s a noticeable increase in the risk of recurrent coronary heart disease events."

The researchers followed nearly 1000 people under 60 who had heart attacks as they returned to work. After six years, 21.5 percent had suffered another.

Working longer hours - 55 or more - was linked to a twofold increase in the risk of a second attack. Most were men. 

"To reduce the risk of coronary heart disease recurrence, secondary prevention interventions aimed at reducing the number of working hours should be evaluated in future studies," said Dr Trudel. 

"Long working hours should be assessed as part of early and subsequent routine clinical follow-up to improve the prognosis of post-heart attack patients."

As an observational study - believed to be the first to look at secondary heart attacks and working conditions - a causal link couldn't be proven. The study also found people who work long hours are also more likely to have stressful jobs, be physically inactive, drink alcohol and smoke - all of which can contribute to poor health - but even when these factors were taken into account, long hours still appeared to increase the risk of second heart attacks.

The biggest risk emerged after four years, suggesting the risk was cumulative.

"The present study suggests that the effect of long working hours... is of higher magnitude approximately four years following return to work," the study, published in the Journal of the American College of Cardiology, says.

"This finding could be explained by the need for a sufficient duration of exposure to be cumulated (chronic exposure), an induction period required for long working hours to exert its adverse effect, or both."

There are now calls for more research into the links between long hours and heart attacks.

"The study provides a new piece of research evidence that work-related factors play an important role in coronary heart disease prognosis," said Jian Li, public health professor at the University of California, in an accompanying editorial.

"Occupational health services are urgently needed to be incorporated into secondary prevention of cardiovascular disease."