Could cold weather be bad for your heart? Research suggests it could be.
The American Journal of Preventive Cardiology recently published a study observing whether “non-optimal temperatures” are associated with heart disease. In the study, scientists used data from 2000 to 2o2o and examined 819 counties across the United States, daily temperature data from Oregon State University’s PRISM Climate Group, and over 14 million deaths from cardiovascular diseases (heart disease, stroke, and related conditions). Here is what they found.
The Optimal Average Monthly Temperature
The study identified an average optimal monthly temperature of about 73.8°F (23.2°C). This was the average monthly temperature at which cardiovascular death rates were the lowest. But rather than using this temperature as a “magic number” that everyone should live in year-round, it was used as a reference point for measuring the impacts of “non-optimal” temperatures. For example, months with temperatures averaging above 73.8°F were considered “heat exposure,” and months with temperatures below 73.8°F were considered “cold exposure.”
73.8°F is merely a “sweet spot” where cardiovascular deaths were at their lowest in the 20 years between 2000 and 2020.
Heat Exposure, Cold Exposure, and Cardiovascular Health
The study found that exposure to non-optimal temperatures can increase the risk of dying from cardiovascular disease.
While the relationship was not straightforward (both extreme hot and cold temperatures increased risk), cold weather was responsible for the vast majority of temperature-related cardiovascular deaths. Each year, it was estimated that 2,242 deaths were linked to hot temperatures and 42,735 linked to cold temperatures. Cold weather was associated with roughly 19 times more cardiovascular deaths than hot weather.
Other studies have been consistent with these findings. A similar study conducted by the Journal of the American College of Cardiology found that, of the global 1,801,513 annual cardiovascular deaths associated with non-optimal temperatures between 2000 and 2019, “cold-related deaths accounted for 8.20%, whereas heat-related deaths accounted for 0.66%.”
High Exposure to Colder Temperatures
The study not only measured how dangerous the cold and heat are, but it also measured how often people are exposed to them. Research found that the optimal temperature of 73.8°F was warmer than 80.7% of the county-months that were used to measure temperature. This means that about four out of every five months were colder than the optimal temperature. The U.S. population spends much more time in temperatures below 73.8°F.
This helps explain why cold-attributed deaths are much higher than heat-attributed deaths. Because Americans are exposed to below-optimal temperatures much more than above-optimal temperatures, the cold is attributed to far more cardiovascular disease deaths.
What Does Cold Weather Do?
Researchers believe that cold weather may increase the risk of cardiovascular death because of what it does to the body. When temperatures drop, the body must work hard to maintain warmth. Blood vessels narrow, raising blood pressure and increasing oxygen demand. Cold temperatures can also throw off plaque stability in the arteries, increasing the risk of heart attacks and strokes.
These effects can be especially dangerous for people with underlying chronic conditions, such as cardio-kidney-metabolic disease.
The Bottom Line
After analyzing more than 14 million cardiovascular deaths across 819 U.S. counties between 2000 and 2020, non-optimal temperatures were associated with a significant risk of dying of cardiovascular disease. Cold temperatures were associated with the vast majority of temperature-related deaths, as Americans are exposed to colder weather much more often.
While both hot and cold temperatures were associated with increased cardiovascular risk, the researchers found that cold weather accounted for the overwhelming majority of temperature-related cardiovascular deaths. The findings add to a growing body of evidence suggesting that colder conditions may place a greater strain on the cardiovascular system than many people realize.
