Jack Frost doesn’t just nip at your nose. Sudden cold fronts can increase your risk of heart attack too. According to a study of hospital admissions in England and Wales, for every degree Celsius that the temperature dropped in a day — particularly when it got colder than 12 C (53 F) — the number of heart attacks reported by hospitals increased by 200.
(More on Time.com: Can Catching a Cold Make You Fat?)
Although the study couldn’t explain the phenomenon, doctors have long known that cold weather can thicken blood and promote clotting. Further, as the Los Angeles Times reported:
[B]lood vessels narrow in cold temperatures — and that could raise blood pressure because more pressure is needed to move blood through those narrowed vessels.
In the Mount Sinai School of Medicine’s Focus on Healthy Aging newsletter, cardiologist Bruce Darrow notes that cold weather brings on other changes in the body — for instance, your body reduces blood flow to your extremities (fingers and toes) in cold weather. In addition, cold temperatures may affect the body’s production of hormones that regulate blood pressure.
In the study, people who were older than 75 or had a history of heart disease were most vulnerable to dips in temperature. But those taking a daily baby aspirin — an important preventive treatment for heart attack — were less likely to have a heart attack than people who didn’t take the drug. (More on Time.com: 5 Ways to Beat the Winter Doldrums)
The best way to prevent a cold weather–induced heart problem? Stay toasty inside, or if you do go out, bundle up in layers.