In a study from Harvard University and elsewhere, scientists found extreme temperatures – both hot and cold – may increase the risk of dying for people with heart disease, especially those with heart failure.
The study analyzed more than 32 million heart deaths over four decades in 27 countries across five continents. It found more deaths on days when temperatures were at their highest or lowest.
Heart disease is the leading cause of death around the world.
But cardiovascular death rates have fallen substantially since the 1960s because of efforts to identify and address risk factors such as tobacco use, physical inactivity, Type 2 diabetes, and high blood pressure.
In the study, the team analyzed cardiovascular disease-related deaths during the hottest and coldest days from 1979 to 2019.
Deaths from any cardiovascular disease, and individually from ischemic heart disease, stroke, heart failure, and arrhythmia.
They compared the death rates on extreme temperature days in 567 cities to rates from days with optimal temperatures in the same cities.
The analysis found 2.2 additional deaths for every 1,000 cardiovascular deaths recorded on the hottest days. But extremely cold days appeared to be more dangerous.
On those days, researchers found 9.1 additional deaths for every 1,000 heart deaths.
People with heart failure appeared to be most sensitive to extreme temperature swings, with 2.6 additional deaths on the hottest days and 12.8 more deaths on extremely cold days.
To prevent cardiovascular deaths during extreme heat or cold, the researchers suggest developing warning systems and advice for at-risk populations.
In such statements, scientists may provide more direction to healthcare professionals, as well as identify clinical data gaps and future priorities for research.
For more information about heart health, please see recent studies about how to cut heart attack risk by half, and results showing people who do not exercise may have instant death from a heart attack.
The study was conducted by Dr. Barrak Alahmad et al and published in Circulation.
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