Is exercise dangerous? It seems so, with cases of young, healthy athletes collapsing suddenly and dying of cardiac arrest while playing sport becoming more common. But a new study by researchers from the University of British Columbia in Canada suggests that while it is a problem that warrants attention, don't blame sport. Reviewing coroners' reports, Dr Andrew Krahn and a team of researchers found there were 174 cases of presumed sudden death in Ontario, Canada in 2008, in people aged two to 40 years. Heart disease was present in about seven in 10 cases, 78 per cent of which was unrecognised. Most victims were male between the ages of 18 and 40. Most events (72 per cent) occurred at home. Only one third of events involving children or adolescents and just 9 per cent of events in adults happened during moderate or vigorous exercise. These findings dispel a myth that sudden cardiac death often takes place during rigorous physical activity. "Put it this way: if you have a 13-year-old kid who is not the star athlete who dies at home watching television, it doesn't make the news," says Krahn. "But if the same kid is a high-school quarterback or hockey star, then it's covered." How can unrecognised heart disease be caught before it causes sudden death, particularly in young people? Krahn suggests more attention be paid to possible warning signs such as fainting. He believes that teachers, coaches and an increase in public awareness may be key to detecting risk, thereby ensuring prevention and formal medical evaluation and therapy. "I would advocate careful screening of people who faint, and educating health care professionals, so when warning signs present themselves, they are recognised and the information is passed on to the right people," he says. Dr Beth Abramson, a researcher with the Heart & Stroke Foundation of Canada, says training in cardiopulmonary resuscitation (CPR) and placement of automated external defibrillators (AEDs) in schools, arenas and gyms - making them "as available as fire extinguishers" - can save many lives. "The odds of surviving a cardiac arrest can increase to up to 75 per cent when early CPR is used in combination with an AED in the first few minutes," Abramson says. The importance of AEDs was demonstrated this past summer when NHL hockey player Brett MacLean, 23, suffered a cardiac arrest at an arena in Ontario during a pick-up game with friends. Players immediately performed CPR on the ice, while a spectator retrieved the AED in the arena. Through their swift actions, MacLean survived and is recovering.