A large analysis of studies finds shift work linked to increased risk for heart attack and stroke
An international team of researchers (Canada and Norway) analyzed results from 34 studies which involved over two million individuals and found that shift work is linked to a higher risk of vascular events such as heart attack and stroke. This study is the largest examination of shift work and vascular events to date.
For this study researchers led by Dr. Daniel G. Hackman, BSc, MD, PhD, FRCPC, associate professor in the Department of Epidemiology and Biostatistics at Western University in Canada and scientist at the Robarts Research Institute, Stroke Prevention and Atherosclerosis Research Centre, gathered and analyzed the results of 34 studies covering over 2 million people and compared shift workers to regular daytime workers or the general population.
Shift work was defined as evening shifts, irregular or unspecified shifts, mixed schedules, night shifts and rotating shifts.
Among the people in the study more than 17,359 had some kind of coronary event, 6598 had myocardial infarctions (heart attacks), and 1,854 had ischemic stroke caused by lack of blood to the brain. These events were more common in shift workers than others. Shift work as associated to a 23% increased risk for heart attack, 24% increased risk for coronary events and 5% increased risk for stroke.
Nightshifts were associated with the highest increased risk for coronary events at 41%, however, shift work was not associated with an increased death rates from any cause.
The researchers note that although the relative risks were modest they pointed out that the frequency of shift work in the general population means the overall risks are high.
Dr. Hackman said shift workers were more apt to sleeping and eating badly.
“Night shift workers are up all the time and they don’t have a defined rest period. They are in a state of perpetual nervous system activation which is bad for things like obesity and cholesterol,” says Dr. Hackman as reported by BBC News.
The authors say their findings have several implications. Researchers suggest screening programs could help identify and treat risk factors such as high blood pressure, and shift workers could be educated about symptoms that indicate early heart problems.
“If you are a shift worker, know your cardiovascular risk factors cold,” states Dr. Hackman, reported by CBS news, “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.”
This research was published online July 26 in the British Medical Journal.