Global warming may be melting glaciers and forcing polar bears onto land, but doctors warn it could also affect your heart.
"If it really is a few degrees warmer in the next 50 years, we could definitely have more cardiovascular disease," said Dr. Karin Schenck-Gustafsson, of the department of cardiology at Sweden's Karolinska Institute.
On the sidelines of the European Society of Cardiology's annual meeting in Vienna this week, some experts said the issue deserves more attention. It's well-known that people have more heart problems when it's hot.
During the European heat wave in 2003, there were an estimated 35,000 deaths above expected levels in the first two weeks of August. In France alone, nearly 15,000 extra people died when temperatures soared. Experts say much of that was due to heart problems in the elderly worsened by the extreme heat.
The hardening of the heart's arteries is like rust developing on a car, said Dr. Gordon Tomaselli, chief of cardiology at Johns Hopkins University. "Rust develops much more quickly at warm temperatures and so does atherosclerosis," said Tomaselli, who is program chair at the American Heart Association.
In higher temperatures, we sweat to get rid of heat. During that process, blood is sent to the skin where temperatures are cooler, which opens up the blood vessels. In turn, the heart rate rises and blood pressure drops. That combination can be dangerous for older people and those with weakened cardiovascular systems.
Extreme events like the recent devastating fires in Greece may complicate the problem. The increasing number of forest fires that have swept through Southeast Asia in the last decade have also brought a spike in heart disease, experts say.
But because there are so many scientific uncertainties about climate change, like how fast it will occur, or what other factors, such as pollution levels or natural phenomena, might affect it, doctors are unsure what exactly to prescribe.
In addition, there are too many unknowns in connecting global warming and heart disease to make predictions about how many more people will have heart problems in the future.
Other factors may also make climate change more dangerous, such as the fact that in the future the majority of the world's population is expected to live in cities. With concrete skyscrapers, fewer trees and pollution spewed from factories and cars, cities are at least a few degrees hotter than surrounding rural areas.
Doctors also suspect pollution, which is expected to get worse with climate change, contributes to heart disease. They think that when the lungs are irritated by tiny airborne contaminants, that could set off a bad reaction in the heart.
"A lot of cardiovascular risk could be avoided by targeting the urban heat effect," said Diarmid Campbell-Lendrum, a climate change expert at the World Health Organization. Although some European countries have put heat warning systems into place to alert people when they might be at increased risk, more needs to be done, Campbell-Lendrum said.
Still, higher temperatures won't be bad news for everyone. "Skiers aren't going to like it, but warmer weather could encourage some people to exercise more and actually improve their health," said Dr. John Cleland, a heart failure specialist at the University of Hull in Britain.
The human body is not designed to handle extreme heat for long periods of time; mechanisms like sweating are only effective as a temporary fix. But that could change if our environment becomes radically different. Some experts speculate that humans might even develop some kind of biological way to better tolerate heat.
"The problem is that this process of evolutionary adaptation for humans takes not decades, but tens of thousands of years," said Dr. Claudio Ceconi, spokesman for the European Society of Cardiology. "We unfortunately won't be able to evolve quickly enough to keep up."
In the meantime, Cleland said to focus on things we can control, like diet and fitness. "We should think more about going outside for a bicycle ride even when it's not bright and sunny," he said.