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Doctors have long known that heart attacks are more likely to happen early in the day, but they still don’t completely understand why. Recent research has revealed several factors that help to explain it.

Clock watching

Your body has a built-in “clock”—a circadian rhythm that helps keep things on schedule night and day. It regulates a variety of everyday functions like sleeping, eating, and even your heartbeat. While you sleep, your body gets busy preparing itself for the demands of the next day. After you wake up, the body continues to make adjustments as it follows its natural daily rhythm.

Some of those morning changes could raise your risk of heart trouble:

• Stress hormones are released into your bloodstream.
• Blood pressure goes up. That could tax your blood vessels.
• Blood vessels are less flexible, making it easier for harmful plaque to build up.
• Blood is thicker and more likely to clot in damaged blood vessels.
• The body’s ability to repair damaged blood vessel linings may be temporarily reduced.

The risk of a heart attack is highest during the first few hours after you wake up. Some research suggests it’s about three times higher than in the evening. There is also evidence that morning heart attacks tend to do more damage.

What else might contribute?

One recent study, published in Circulation Research, found that during the morning, heart patients have lower blood levels of a newly discovered group of protective molecules. Replacing the missing molecules appeared to reduce blood vessel inflammation. That could pave the way for new treatments.

Emotional stress may also be a risk factor for heart disease, although more research is needed to prove it. Some experts think worries about facing another day at a stressful job may contribute to early-morning heart risk.

Monday, Monday

Morning isn’t the only time to beware of; the day of the week seems to affect heart risk too. A large review of research studies found a clear trend: people are more likely to have a heart attack or sudden cardiac death on Monday. Is it another possible effect of job stress as we go back to work after the weekend? Maybe. But one study found irregular heartbeat problems peaked on Monday even in people who are retired. We still have more to learn about Monday’s risks.

What to do

There aren’t any proven ways to reduce morning heart attack risk specifically. The best things you can do to lower your chance of a morning heart attack are the same things that reduce your overall heart disease risk:

• Don’t smoke
• Keep blood pressure and cholesterol levels within your prescribed range
• Maintain a healthy weight
• Eat a heart-healthy diet, limiting sodium, sugar, and saturated or trans fat
• Exercise five days a week for a total of 30 minutes a day
• Limit alcohol to no more than one drink a day for average women and two drinks a day for men
• Control your blood sugar if you have diabetes

If you’re concerned that stress might contribute to your heart attack risk, talk with your doctor or a mental health provider. They can help you learn self-help techniques or provide professional treatment if needed.

Living with heart risks

Mornings may come with a certain amount of risk, but doing what you can to improve your heart health can help you wake up each day with greater confidence and peace of mind. Talk with your doctor about additional steps you can take to enjoy a longer, heart-healthier life.

Have you had a heart attack? What time of day did it happen? What risk factors do you believe led to it? Add a comment below to share your experience with our community.