Endurance Runners 10 Times More Likely to Die of Heat Stroke than Cardiac Events

Runners are more likely to die of heat stroke than cardiac events during endurance races in warm climates, a new study reveals.

Running is the best cardio activity, but too much of it could be harmful. The longstanding ill health effects of endurance running, which is defined as running over distances of more than 5 miles, has been well documented. These runners end their day with caloric deficit.

The new study found that endurance athletes are 10 times more likely to die of heat stroke than cardiac events during endurance races in warm climates. Two of the most recognized causes of sudden death till date, during such endurance races, are arrhythmic death and heat stroke. But out of these two, it is the undetected heart condition that grabs the attention of the medical community.

"This research shows that heat stroke is a real threat to marathon and long-distance runners; however, there are no clinical studies of potential strategies to prevent heat stroke during these types of events," said Sami Viskin, MD, senior author of the study and a cardiologist at Tel Aviv Medical Center.

Arrhythmic death is the sudden death caused by undetected heart disease in young and healthy people. As endurance races of more than 10 km are gaining popularity, researchers wanted to check how many life-threatening events, during such races, were caused by heat stroke as compared to cardiac events.

A life threatening event is a condition which requires mechanical and hospitalization in an intensive care unit.

In this study, the researchers examined the data on all deaths and emergency hospitalization at 14 races in Tel Aviv from 2007-2013.  A total of 137,580 runners were evaluated. During the study period, just two serious cardiac events were reported, but none were fatal or life threatening. However, during the same time, there were 21 serious cases of heat stroke that included two fatal cases and 12 life-threatening ones.

The Israeli sports law recommends that ECG screening is needed for those who are organized in teams or associations, but not for those in public endurance races. All the runners were made to provide personal statement that confirmed the state of good health.

At the 2013 race, 513 runners were surveyed on whether or not they had undergone ECG screening. It was noticed that just 35 percent of them had an ECG done in the previous year and 46 percent of them had an ECG in the past five years. This reduced the possibility that the low number of cardiac events stemmed from at-risk runners being screened out before the race.

"It's important that clinicians educate runners on the ways to minimize their risk of heat stroke, including allowing 10-14 days to adjust to a warm climate, discouraging running if a person is ill or was recently ill because a pre-existing fever impairs the body's ability to dissipate additional heat stress, and developing better methods of monitoring body core temperature during physical activity," said Viskin.

The finding was documented in the Journal of the American College of Cardiology.