“Working more than eight hours a day raises the risk of heart disease by 80%,” reported the Daily Mail, while The Sun said “overtime`s a killer…literally”.
The news is based on a study that pooled the results of previous studies looking at the association between “longer working hours” and coronary heart disease (CHD). Those working longer hours were shown to be 80% more at risk of CHD.
However, there were significant inconsistencies between the studies that cast serious doubt on the validity of any conclusion about a link between CHD and working hours. These inconsistencies included the definitions of “longer working hours” (from 40 to 65 hours a week).
The studies were also inconsistent in their type, making the overall pooling inappropriate. When the researchers removed less well-designed studies from their analysis, the estimate was lower; in the region of 40% increased risk.
Finally, as only one of the studies was from the UK, the findings may not be applicable to workers in this country.
This study suggests that those who work longer hours may have an increased risk of CHD, but stops well short of proving that one causes the other. There are many other factors that may influence this association.
“Balance between work and leisure time is important,” says the lead author of the study, Dr. Marianna Virtanen, M.D., an epidemiologist at the Finnish Institute of Occupational Health and University College London. “If you work long hours, the fact is that you may be exposed to higher stress levels and you do not have enough time to take care of your health.”
Doctors “should include long working hours on their list of potential risk factors” for heart disease, she adds.
Dr. Virtanen and her colleagues followed more than 6,000 British civil servants with no history of heart disease for an average of 11 years. The participants were all drawn from a larger, ongoing study known as Whitehall II that began in 1985.
During the study, a total of 369 people had heart attacks (some of them fatal) or were diagnosed with heart disease after seeking medical attention for chest pain.
Compared to people who worked seven hours a day, those who worked 10 to 12 hours a day had a 56 percent increased risk of heart disease, heart attack, or death. Those who worked for 8 to 10 hours a day were not at increased risk.