If you have heart trouble, beware of days that are very hot or very cold. For those at risk of death from cardiovascular disease due to obesity, diabetes or related conditions, special care should be taken to avoid extreme temperatures like those experienced during heat waves and cold spells. Research published in Circulation demonstrates that extreme temperatures increase the risk of premature cardiovascular death.

Heart problems are the leading cause of death in the U.S. The risk of complications goes up significantly when temperatures dip or climb.

“This might be because people become exhausted due to the sustained strain on their cardiovascular systems without relief, or health systems become overstretched and ambulances take longer to reach emergency cases,” warns researcher Adrian G. Barnett, Ph.D. “We suspect that people take better protective actions during prolonged cold weather, which might be why we did not find as great a risk of CVD (cardiovascular death) during cold spells.”

Spending a few hours daily in a temperate environment can help reduce heat- and cold-related illnesses and deaths, Barnett says.