Though deaths during races do happen, the risk of collapsing or even dying during a marathon is relatively low, according to an Ottawa cardiologist who studies sudden cardiac death in sport.

On Sunday a man in his 30s collapsed and later died while taking part in one of races during Ottawa Race Weekend, though it is not clear in which race he was running.

Ten other people were taken to hospital Sunday, when the half marathon and marathon were taking place.

But Dr. Andrew Pipe, a doctor at the University of Ottawa Heart Institute who focuses on cardiovascular collapse and sudden cardiac death in sport, says deaths during sporting activities "are exceptionally rare."

According to a study in the New England Journal of Medicine that looked at the incidence of cardiac arrests and deaths of 10.9 million marathon and half-marathon runners over a decade between 2000 and 2010, 59 suffered cardiac arrests and 42 died.

The overall incidence of sudden cardiac arrest was 0.54 per 100,000 people, the study found, though it was higher (0.9 per 100,000 people) among men, and higher among marathon runners over half-marathon runners (1.01 compared with 0.27 per 100,000).

Pipe, who has run in 14 marathons, says the personal history of the person exercising has more bearing on the health risk than the exercise itself.

He said a lot of problems people experience comes down to age, gender, and genetics, and says just because someone is physically fit doesn't mean the same for their heart.

"You can still have significant coronary artery disease, particularly if you have a family history," he said.

Pipe says everyone can benefit from physical activity, even if it's not to the athletic levels. (CBC)

Genetics, family history are factors

For people over the age of 35, the "overwhelming majority" of deaths are because of common coronary artery disease, he said.

But the cardiac failure usually doesn't come out of the blue. People often experience symptoms like chest pain, discomfort, or unusual breathlessness in the weeks or months before their death, he said.

He said anyone who experiences any of these symptoms while exercising normally should see their doctor.

The risk of cardiovascular disease is also lower in women than men of the same age, until they reach menopause, but the symptoms can also manifest differently, he said.

In younger people who suddenly collapse or die, it often comes down to genetics and a family history of heart disease.

Flowers have been left near where the runner collapsed along the Ottawa marathon route, in an apparent memorial. (Krystalle Ramlakhan/CBC)

High blood pressure, high cholesterol, being a smoker or overweight can also be problematic, he said.

Furthermore, he said the most common causes of collapse in a marathon are unrelated to heart disease — heat illness, heat injury and dehydration.

Running better than not

Pipe stresses even though there are risks associated with endurance activity, such as running a marathon, it's better to exercise than not.

"There is absolutely no question that the risk of cardiovascular events is reduced dramatically among those who are active on a regular basis, and that's particularly true of those who run marathons," he said.

"Everyone can benefit from physical activity and you don't have to have athletic levels of physical activity to derive the cardiovascular benefits."

That can be as simple as walking one's dog daily, he said.

Be prepared

Even if someone doesn't have an underlying heart condition there are ways to ensure they don't suffer problems when participating in a marathon, he said.

Those include:

Train properly.

Prepare for the day's weather conditions appropriately.

Set a pace that's reasonable for the conditions, taking into account heat, humidity.

Ensure that you take fluids appropriately.

"Assuming that the preparation has been appropriate, one can very safely complete a marathon event."