Shift work raises risk of heart attack, stroke
Published Thursday, July 26, 2012 3:59PM MDT
Last Updated Thursday, July 26, 2012 5:57PM MDT
Shift work has long been associated with unhealthy lifestyles and sleep deprivation, but a new study has now linked irregular work hours to more serious problems -- increased risks of heart attacks and strokes.
A team of international researchers, including Canadian doctors and professors, analysed 34 studies involving more than two million people and found that shift work increases the risk of a heart attack by 25 per cent and stroke by 5 per cent.
Shift work was defined as evening shifts, irregular or unspecified shifts, mixed schedules, night shifts and rotating shifts – essentially anything but a standard 9-5 job. Control groups consisted of day workers or the general population.
Night shifts were associated with the biggest increase in risk for coronary problems -- 41 per cent.
The risks remained consistent even after researchers factored in study participants’ lifestyle choices and socioeconomic status, as well as the quality of the individual studies they analyzed.
However, there was no evidence that shift work increased death rates from any cause.
While the risk increases are not huge, one of the study authors says they still have a significant impact since an estimated 33 per cent of Canadians perform some type of shift work.
“To put it in that perspective, about 1 in 14 heart attacks and 1 in 40 strokes are directly related to the effects of shift work,” Dr. Daniel Hackam, who teaches at Western University in London, told CTV News. “So it’s quite big.”
Numerous studies and anecdotal evidence have associated shift work with sleep disorders, elevated cholesterol levels and high blood pressure, among other health problems.
The latest study, published Thursday on the British Medical Journal’s website, is the largest analysis yet of the link between shift work and vascular problems.
The authors noted several caveats, including the fact that all the studies they analysed were observational and that different studies adjusted for different risk factors.
But they note that previous studies have found that even a single overnight shift can increase a person’s blood pressure and heart rate.
“A human being is just not programmed to work at these odd hours,” Hackam said, noting that shift work disrupts the circadian rhythm, or the human body clock, often forces people to eat in the middle of the night and hinders regular exercise.
“And this is only going to continue because our society is moving ever more to a 24-hour system,” he said.
Leigh Anne Dunlop, a Toronto paramedic who typically works 12-hour shifts, said switching from day to night shifts can be hard on her body and affects her sleep.
“When you work night shifts, it’s more stress on your body…but if you can monitor that, I try to sleep more the night before,” she said.
Dunlop said she eats a healthy diet and works out in between shifts. She also focuses on the benefits of her job, such as more time off between stretches of long shifts.
Supervisor Gary Wright said Toronto EMS is considering an overhaul of the paramedics’ schedules to lessen the impact on their bodies and health.
“We’ve had the current schedule for 35 years and we are looking at redesigning a schedule that will better match their body’s own biological clock rhythm,” he said.
The latest study “really drives home the point that we need to look at change here,” he said.
“I have been a paramedic for 32 years, 25 years on the road. It is difficult,” he said. “I found night shifts very much a struggle. It does affect your health… Your body temperature starts to go down in the middle of the night.”
Dr. Derek So, a cardiologist at the University of Ottawa Heart Institute, said the new findings “might be a wake up call for a lot of shift workers to reflect on some of their habits that could be unhealthy at this point.”
Employers and family physicians should also take note of the study, So told CTV News.
“Now we have over two million patients in this study. That should be a signal that health care providers should take note of,” he said.
“This tells us these risk factors should be addressed, and it’s a good time to start thinking about it and start moving on it rather than waiting for more evidence.”
The key message, Hackam said, is that shift workers should be vigilant about their health and know their risks.
He recommends that shift workers:
- Get their blood pressure and cholesterol levels checked
- Get their waistlines measured
- Quit smoking if they do
- Take breaks at work to de-stress
- Talk to their employers about workplace health programs or other initiatives
With a report from CTV medical specialist Avis Favaro and producer Elizabeth St. Philip