A new study led by researchers from Harvard T.H. Chan School of Public Health reveals that both very hot and very cold temperatures can increase the risk of death for people with heart failure.
The study focused on patients in Sweden and found that the danger from extreme heat has been growing in recent years, possibly due to climate change.
As climate change causes more frequent and intense heatwaves and cold spells, health experts are becoming more concerned about how these temperature extremes affect people’s health.
It’s already known that unusual weather can be hard on the heart, but this new research adds stronger evidence showing that people with heart failure are especially at risk.
Heart failure is a serious condition where the heart cannot pump blood as well as it should. People with heart failure are already more vulnerable to health complications, and this study suggests that extreme temperatures may increase their risk of dying.
The study, published in JAMA Cardiology, looked at the deaths of over 250,000 people in Sweden who had heart failure and died between 2006 and 2021. The researchers wanted to know if the temperatures around the time of death played a role.
To do this, they used weather data and pollution levels from each person’s local area, matched to their home address.
They looked at the outdoor temperatures during the seven days leading up to each death and compared them to other days with similar conditions but no death. The goal was to see if unusually hot or cold weather increased the risk of dying.
The researchers found a clear U-shaped curve, meaning that death risk was higher during both cold and hot weather—especially during cold spells. During the entire study period, cold temperatures increased overall death rates by 13% and deaths from heart disease by 16%.
High temperatures increased overall death rates by 5% and heart-related deaths by 8%, especially in the later years of the study.
From 2014 to 2021, the risk linked to heat became noticeably stronger than it had been from 2006 to 2013. This suggests that rising temperatures caused by climate change may be making heatwaves more dangerous, especially for those with existing heart problems.
Certain groups of people were more affected than others. Men, people with diabetes, and those taking diuretics (a type of medication often used in heart failure) were more likely to die during cold weather. On hot days, patients with atrial fibrillation (a heart rhythm disorder) and those living in areas with higher ozone pollution levels faced more risk.
This research highlights the need to protect vulnerable groups, especially people with heart failure, from extreme weather. Doctors and public health officials may need to give extra guidance to these patients during heatwaves and cold snaps.
In conclusion, this large nationwide study shows that even short-term exposure to extreme temperatures can raise the risk of death in people with heart failure. And as our climate continues to change, the danger from heat seems to be growing. More efforts are needed to protect at-risk people from the harmful effects of extreme weather.
If you care about heart disease, please read studies about a big cause of heart failure, and common blood test could advance heart failure treatment.
For more health information, please see recent studies about a new way to repair human heart, and results showing drinking coffee may help reduce heart failure risk.
The study is published in JAMA Cardiology.
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