BEIJING, Sept. 6 (Xinhuanet) -- If the effects of global warming on the environment don't concern you, maybe you should think about your heart, doctors warn.

"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.

There were an estimated 35,000 deaths above expected levels in the first two weeks of August during 2003's Europe heat wave. Nearly 15,000 extra people died in France 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.

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.

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.