Urban legend warns shoveling snow causes heart attacks, and the legend seems all too accurate, especially for male wintery excavators with a family history of premature cardiovascular disease. However, until recently this warning was based on anecdotal reports.

Two of the most important cardiology associations in the US include snow -shoveling on their websites as a high risk physical activity, but all the citation references indicate that this warning was based one or two incidents.

"We thought that this evidence should not be enough to convince us that snow -shoveling is potentially dangerous, " says Adrian Baranchuk, a professor in Queen's School of Medicine and a cardiologist at Kingston General Hospital.

Dr. Baranchuk and his team retrospectively reviewed KGH patient records from the two previous winter seasons and discovered that of the 500 patients who came to the hospital with heart problems during this period, 7 per cent (35 patients) had started experiencing symptoms while shoveling snow.

"That is a huge number," says Dr. Baranchuk. "7 per cent of anything in medicine is a significant proportion. Also, if we take into account that we may have missed some patients who did not mention that they were shoveling snow around the time that the episode occurred, that number could easily double."

The team also identified three main factors that put individuals at a high risk when shoveling snow. The number one factor was gender (31 of the 35 patients were male), the second was a family history of premature coronary artery disease (20 of the 35 patients), and the third was smoking (16 out of 35 patients).

The second two factors may carry much more weight than the first, however, since the team could not correct for high rate of snow shoveling among men in their sample.

A history of regularly taking four or more cardiac medications was found to be preventative.

Dr. Baranchuk collaborated on this study with Wilma Hopman (Department of Community Health and Epidemiology, KGH Clinical Research Centre), William McIntyre, (Queen's medical resident), and Salina Chan and David Schogstad-Stubbs (Queen's medical students). These findings were recently published in Clinical Research in Cardiology.