LONDON, (Reuters) – People working 10 or 11 hours a  day are more likely to suffer serious heart problems, including  heart attacks, than those clocking off after seven hours,  researchers said yesterday.

The finding, from an 11-year study of 6,000 British civil  servants, does not provide definitive proof that long hours  cause coronary heart disease but it does show a clear link,  which experts said may be due to stress.

In all, there were 369 cases of death due to heart disease,  non-fatal heart attacks and angina among the London-based study  group — and the risk of having an adverse event was 60 percent  higher for those who worked three to four hours overtime.Working an extra one to two hours beyond a normal seven-hour  day was not associated with increased risk.

“It seems there might a threshold, so it is not so bad if  you work another hour or so more than usual,” said Dr Marianna  Virtanen, an epidemiologist at the Finnish Institute of  Occupational Health and University College London.