Does working the late shift increase your risk of heart attack?

Working the night shift just doesn't seem to have many perks. In May, Danish researchers found that women who worked the graveyard shift were more than twice as likely to develop breast cancer. Now a British study finds that working while most people are sleeping could mean bad news for your heart. The expansive new study suggests that people who work the graveyard shift are at a higher risk of heart attack and stroke compared with those working normal daytime hours. Here's what you should know:

What did the study find?

Researchers pored over 34 clinical studies for data on more than 2 million people who worked shifts that weren't 9-to-5, and reported the findings in the British Medical Journal. The study authors found that late-shift workers showed a 23 percent increased risk of heart attack and a 5 percent increased risk of stroke. The team also determined that people who worked the latest night shifts were at the highest risk of suffering a coronary event, with a 41 percent increased risk. However, researchers note that late-shift workers were not more likely to die from any of these heart-related events compared with their sunlight-seeing peers.

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Why the increase?

It probably isn't just the work itself, but rather a combination of interrelated factors in a late-shift worker's life. "A lack of sleep, poor eating habits, and lower levels of physical activity could plague those who work irregular hours and drive up the risk of vascular disease," says Stacey Schott at ABC News. The risks were still present even when unhealthy eating, smoking, and socioeconomic status were accounted for. It seems like late-night workers "must be contented with working in a state akin to constant debilitating jetlag," says Barbara Ellen at the Guardian. Working the night shift could also be disruptive to the body's circadian rhythms, which mounting evidence has shown to be important to vascular health.

What can a late-night worker do to stay healthy?

They can practice extra vigilance. "Know your cardiovascular risk factors cold," says study author Dr. Daniel G. Hackman. Night workers should consult with their doctors and ask for measurement of "blood pressure, waist circumference, cholesterol, triglycerides, and fasting blood sugar." Unfortunately, night work is a "necessary evil for more than a third of the working population," says ABC News' Schott. It's best to know what you're up against, and plan accordingly.

Sources: ABC News, CBS News, Guardian, WebMD