Long work hours may raise stroke risk

People who work long hours face a higher risk of stroke than those who put in a standard work week, a large review suggests.

British researchers analyzed data from studies on more than 603,000 men and women from Europe, the U.S. and Australia who were followed for about eight years. They looked at the effects of longer work hours on cardiovascular disease.

Those who worked 55 or more hours a week showed about a 1.33 times or 33 per cent higher risk of stroke compared with those who clocked 35 to 40 hours a week, Mika Kivimäki, a professor of epidemiology at University College London and his co-authors said in Wednesday's online issue of The Lancet.

There was also a weaker association, about 10 per cent, between long working hours and coronary heart disease, such as heart attacks and cardiac deaths.

"If a person works long hours, it's extra important that he or she tries to keep healthy habits," such as keep your blood pressure, cholesterol and glucose levels in the normal range, maintain a healthy weight, eat healthily, not smoke or quit and get enough exercise, said Kivimäki.

The associations did not vary between men and women, by age, socioeconomic status or by geographical region, Kivimäki said, which suggests the findings were robust.

No one knows how working long hours adds to stroke risk. Kivimäki pointed to three possibilities:

• A toxic effect from stress itself.
• Extensive sitting and sedentariness on the job.
• Failure to follow a healthy diet and exercise routine outside of work.

During the study period, there were 1,722 strokes.

The research wasn't able to assess if there is a cause-and-effect relationship.

"I think it's important to remember that although there are these potential harmful effects, it can also be so that working hard can also lead to many good things," said Kivimäki. "I think it's not so black and white."

'Wear and tear of life'

He suggested the European Union's work time directive, which gives employees the right to limit their working hours to 48 hours on average, is the best approach because it gives employees the last say.

A century ago, in an article about atherosclerosis or hardening of the arteries, Canadian physician William Osler wrote that the main cause of heart attack was "wear and tear of life."

"He had intuition and we put data on that," Kivimäki said.

Everyone should have their risk factor profile assessed by their doctor, and if they are working extra hours or longer shifts, that's also important information, said Dr. Andreas Wielgosz, a professor of cardiology at the University of Ottawa and a spokesman for the Heart and Stroke Foundation. He was not involved in the research.

Working long hours isn't necessarily a personal choice since an individual's economic situation could necessitate it.

Wielgosz called the review a strong reminder to pay attention to working hours.

"I think the first line of responsibility is with the individuals, the employees, to communicate to their personal physician the fact that they are working extra hours," Wielgosz said.

Where possible, employers should try to facilitate healthy lifestyles among employees, such as by offering smoking cessation programs, opportunities for physical activity and blood pressuring monitoring, the cardiologist suggested.

Dr. Urban Janlert from Umeå University in Sweden wrote a journal comment published with the research.

Janlert called the study pioneering in its large scale, but also noted its limitations, such as have participants self-report their working time only once.

Janlert said researchers could test their results experimentally by randomly assigning some individuals who work long hours to reduced working hours and measuring the consequences, such as stress response, blood pressure, sedentary and sleep time.

The study was funded by a variety of European research councils and the U.S. National Institutes of Health.