July 26, 2012 -- Working the night shift or any non-traditional schedule may increase your risk of heart attack and stroke, a study shows.
Previous research has linked shift work to heart disease and stroke risk factors including high blood pressure, high cholesterol levels, and diabetes. Now, researchers who reviewed 34 studies of more than 2 million people found that shift workers are also more likely to have a heart attack or stroke.
The new study "provides a firm anchor to state that shift work is associated with an increased risk of heart attack and stroke. The relationship is probably causal, but it is difficult to say that on the basis of observational studies alone," says study researcher Daniel G. Hackam, MD, PhD. He is an assistant professor of medicine at the University of Western Ontario, Canada.
The study is published online in the journal BMJ.
Exactly how shift work increases the risk for heart attack and stroke is not fully understood. It may disrupt the body's natural sleep-wake cycle. Shift workers may also be more likely to smoke and eat an unhealthy diet. And they may be less likely to get regular physical activity.
In the study, shift work was defined as:
any non-daytime schedule
Night shift workers in the study had the highest risk for heart attack and stroke, particularly in the first 10 to 15 years on the job.
Compared to people who worked during the day, shift workers were:
23% more likely to have a heart attack
5% more likely to have a stroke
But the study also showed that shift workers were not more likely to die compared to daytime workers.
The findings held up even when the researchers took into account unhealthy behaviors and other factors that increase heart attack and stroke risk.
Prevention is key, Hackam says. "If you are a shift worker, know your cardiovascular risk factors cold. Go see your family doctor and get an annual physical. And ask for measurement of your blood pressure, waist circumference, cholesterol, triglycerides, and fasting blood sugar."