Shift workers, especially those working overnight, are at a higher risk for having a stroke or heart attack, an analysis finds.

Long-term care nurses and nursing assistants often work various shifts, which other studies have indicated can raise their risk for diabetes or obesity.

For the purpose of this study, shift work was defined as evening shifts, irregular or unspecified shifts, mixed schedules, night shifts and rotating shifts. A team of Norwegian and Canadian scientists analyzed 34 previous studies involving more than two million participants.

They found that night-shift workers had a 41% increased risk for coronary events. Participants who worked on other shifts had a 23% increased risk for heart attack, a 24% higher risk for coronary events and a 5% higher risk for stroke.

Researcher Dan Hackam, M.D., Ph.D., of the University of Western Ontario, encouraged employers to help shift workers take preventative action.

“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,” Hackam told WebMD.

The study was published Thursday in the British Medical Journal.