Have you heard that shoveling snow can cause a heart attack? Actually, there is some truth to this. The physical demands of shoveling snow are certainly a factor, but even people who are used to yard work can be affected. Extremely cold temperatures can make your heart work harder to keep your body from freezing to death, especially if your heart’s pumping function is already impaired by an existing medical condition.
A growing number of studies are uncovering a link between environmental temperature and heart health. And it’s not just the cold that’s of concern: studies have shown that outdoor temperatures of 108.9 degrees Fahrenheit triple the risk of death from cardiovascular disease. With September 2023 set to be the hottest month on record and global temperatures predicted to rise 1.5 degrees Celsius (2.7 degrees Fahrenheit) above pre-industrial levels over the next decade, heat is becoming a more prevalent threat to heart health.
“We know how it affects our physiology, so we’re certainly going to see an increase in heart attacks as temperatures rise,” said Jennifer Wong, a cardiologist and medical director of noninvasive cardiology at MemorialCare Heart and Vascular Institute in California. She added that medical centers may start to see more patients with symptoms that could lead to a heart attack, such as chest pain, reduced blood flow and increased strain on the heart.
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While there’s no way to control the weather, you can protect your mind from it, and learning more about the dangers is a good first step.
How does cold weather affect the heart?
The human body’s core temperature typically ranges from 97.5 to 98.9 degrees Fahrenheit. When extreme cold starts to lower this body temperature, the body responds by activating the sympathetic nervous system (perhaps best known for triggering a person’s fight-or-flight response). This triggers certain mechanisms to retain as much heat as possible. One such mechanism is vasoconstriction, in which the muscles in the walls of blood vessels narrow to prevent heat loss, says Lakshmi Mehta, a cardiologist at The Ohio State University Wexner Medical Center. Blood, a vital component of thermoregulation, normally distributes heat throughout the body. In extreme cold, the sympathetic nervous system reduces blood flow to the skin to help the body retain warmth.
Constricting blood vessels and reducing blood flow help keep you warm, but they also increase blood pressure. A yet-to-be-peer-reviewed study presented at an American Heart Association meeting earlier this year found that systolic blood pressure (the “top” number in blood pressure measurements that represents how hard your heart pushes against your artery walls as it contracts) tends to be higher in winter than in summer. When blood pressure rises, your heart has to work harder to circulate blood around your body.
“This tension can increase your heart rate and blood pressure, which can trigger cardiac symptoms and even lead to a heart attack in some people,” Mehta says, warning that cold temperatures can also increase your risk of blood clots. This is because cold weather thickens your blood, which can cause platelets to stick together and form clots, which in turn increases your risk of heart attack or stroke.
Heart Risks During the Holiday Season
The Northern Hemisphere’s winter is the time of year when some of the biggest holidays take place, but it also sees an increase in heart attacks. BMJ The study found that heart attacks are more likely to occur on Christmas Eve than on any other holiday. Cold weather, the extra stress that comes with planning the holidays, and the habit of indulging in high-salt, high-cholesterol foods can lead people to forego normal heart-healthy foods and activities. These factors combine to increase the risk of heart attack.
“People may eat out more, drink more alcohol, exercise less, and sleep less,” Mehta explains, “and the excitement of spending time with family and friends may cause them to ignore symptoms or put off addressing them until after the holidays.”
The negative effects of heat on heart health
Both hot and cold can pose a threat to thermoregulation. In response to extreme heat, the sympathetic nervous system increases blood flow to the skin. This, along with vasodilation, or the widening of blood vessels, helps dissipate excess heat, says Craig Crandall, a professor of internal medicine at the University of Texas Southwestern Medical Center, who studies the effects of heat on the cardiovascular system. But on a hot day, pumping more blood to the body’s surfaces puts the heart under strain. The heart has to beat faster to circulate two to four times as much blood per minute than it would in more comfortable climates.
“Your heart has to work harder to keep pumping blood to the rest of your body,” Crandall explains. “Plus, you’re pumping more blood through your skin, [the body] Cool off.”
According to Crandall, when a person continues to feel hot, the brain continues to signal the heart to beat faster, but the heart cannot keep up this condition forever because the increased demand for blood means an increased need for oxygen. Thus, heat stress can overwork the heart muscle and lead to oxygen starvation. “That can lead to some adverse events, especially in people with various cardiac conditions,” Crandall said. For example, people with clogged arteries already have problems delivering oxygen and other nutrients to the heart. The added strain can increase the risk of heart attack.
How to protect your heart
During extreme weather, stay indoors if possible and turn up your heat or air conditioning if necessary. If you must go outside, dress appropriately. Mehta recommends that people with heart disease warm up before going outside into the cold. And if you’re doing heavy work, like shoveling snow, take frequent breaks.
Crandall urges people at high risk of heart disease to stay indoors (at home or in public) as much as possible during heatwaves to keep them cool, and notes that staying well hydrated can help the body lose excess heat through sweating.
Ultimately, most cardiologists agree that the best way to avoid a weather-related heart attack is to reduce your risk of heart disease in the first place. Wong says it’s important to understand the stress that extreme temperatures put on the body and take proper safety precautions in these situations. But it’s equally important to do everything you can to prevent heart disease, like exercising, maintaining a heart-healthy diet, and taking your medications.
