Surprisingly, the association was strongest among workers under the age of 50.
Although the research comes with some important caveats, it is troubling nonetheless, particularly for American workers, who are among the most overworked in the developed world.
The study is just the latest in a series of studies from around the world that have linked long work hours with poorer health outcomes, including poorer mental health and an increased risk of type 2 diabetes.
How the study was done
For the current study, researchers analyzed data collected from questionnaires filled out by 143,592 French adults, aged 18 to 69, who were part of a larger, ongoing research project that began in 2012. The researchers included in their analysis only those participants in the larger study who reported being full-time workers.
The questionnaires asked the participants about their occupation and about their work hours. People were considered to have long work hours if they reported working more than 10 hours for at least 50 days per year.
Among the study’s participants, 29 percent (42,542 individuals) reported working long hours, and 10 percent (14,481) reported working long hours for a decade or longer.
The researchers then combed the participants’ medical data to see who had experienced a stroke after they said they had started to work long hours. They found 1,224 people fit that category.
After controlling the data for age, smoking and other stroke-related risk factors, the researchers looked to see if there was an association between long working hours and an increased risk of stroke. There was. Compared to the people who said they didn’t work long hours, those who said they did had a 29 percent greater risk of stroke.
That increased risk climbed to 45 percent for people who reported working long hours for 10 years or more.
“The association between 10 years of long work hours and stroke seemed stronger for people under the age of 50. This was unexpected,” said Dr. Alexis Descatha, the study’s senior author and a researcher at the French National Institute of Health and Medical Research, in a released statement.
“Further research is needed to explore this finding,” he added.
The study was observational, and therefore can’t prove a direct relationship between long working hours and stroke. Furthermore, the data for the study came from the participants’ own reports of their working hours — reports that may not always have been accurate.
But other studies have also found an association between long working hours and an increased risk of stroke. For example, a review of 20 studies published in The Lancet in 2015 reported that working more than 55 hours a week was associated with an increased risk of stroke and other cardiovascular diseases.
That study suggested that the stress caused by working overtime week after week may trigger inflammation in the body’s blood vessels, which, in turn, may raise the risk of stroke. Behavioral factors associated with long working hours, such as increased alcohol consumption and less physical activity, are also likely to play a role.
Lowering your risk
You may not be able to control your working hours, but you can control other factors related to the risk of stroke by making healthy lifestyle choices. Here are 10 tips from the Mayo Clinic:
- Control high blood pressure (hypertension). Know your numbers and keep them low.
- Quit tobacco. Smoking raises the risk of stroke.
- Control diabetes. You can manage diabetes with diet, exercise, weight control and medication.
- Manage a healthy weight. Being overweight contributes to other stroke risk factors such as high blood pressure, cardiovascular disease and diabetes. Weight loss of as little as 10 pounds may lower your blood pressure and improve your cholesterol levels.
- Eat a diet rich in fruits and vegetables. A diet containing five or more daily servings of fruits or vegetables may reduce your risk of stroke.
- Exercise. Exercise can lower your blood pressure, increase your level of high-density lipoprotein cholesterol, and improve the overall health of your blood vessels and heart. It also helps you lose weight, control diabetes and reduce stress.
- Drink alcohol in moderation, if at all. Heavy alcohol consumption increases your risk of high blood pressure, ischemic strokes and hemorrhagic strokes.
- Treat obstructive sleep apnea, if present. Your health care provider may recommend an overnight oxygen assessment to screen for obstructive sleep apnea (OSA). If obstructive sleep apnea is detected, it may be treated by giving you oxygen at night or having you wear a small device in your mouth.
- Avoid illicit drugs. Certain street drugs, such as cocaine and methamphetamines, are established risk factors for a transient ischemic attack (TIA) or a stroke.
- Manage other medical conditions. If you have any of these conditions, seek treatment to help reduce your risk of stroke: high cholesterol, carotid artery disease, peripheral artery disease, atrial fibrillation (AFib), heart disease or sickle cell disease.
For more information: You’ll find an abstract of the study on Stroke’s website, but the full study is behind a paywall.