"This confirms previous studies that show there is a risk reduction of breast cancer when exercise is involved, but this is the first study to look at activity over an entire lifetime," said Dr. Kerry Courneya, a professor from the U of A's Faculty of Physical Education and Recreation and a co-author on the paper. "This is also the first study that has combined occupational and recreational activity and is the first to look at the intensity and duration of activity, so it's quite exciting."

Courneya and the research team--made up of Dr. Christine Friedenreich and Heather Bryant from the Alberta Cancer Board--compared more than 1200 women who had been recently diagnosed with breast cancer to the same number of women who were cancer-free and looked at the difference between the lifestyle of the two groups. The paper--the second in a series of three--appears in the current edition of Medicine and Science in Sports and Exercise.

Researchers used recall calendars to help participants with their long-term memoryl of the physical activities throughout life. "For example, we might say, 'think back to when you were married--what kind of activity were you doing or where were you working. Or think back to when your second child was born--what sports, if any, were you involved in,'" said Courneya. "This cognitive interviewing technique helps them look at major life events and really recall those times."

The research team specifically found that the greatest breast cancer risk reductions were associated with moderate-intensity occupational activity, with some risk decreases also attributable to moderate-intensity household activity.

"Vigorous activity didn't seem to make a difference, but maybe it's because there was very little vigorous activity reported," said Courneya. "But intensity of the activity was not a major contributor to the breast cancer risk reduction observed in this population, while the frequency and duration of total activity were important determinants for the risk decrease."

Since occupational activity as a source of physical activity in the North American population is declining with increasing mechanization, the influence of occupational activity on breast cancer risk in future generations of women may be weaker than in the cohort of women included in this study who were up to age 80, say the authors. For a beneficial effect of physical activity, populations at risk will have to ensure that recreational activity levels increase to compensate for the decrease in energy expenditure in occupational and household activities that is likely to continue.

"We're starting to accumulate a lot of studies-and ours confirms it--that there is a risk-reduction of breast cancer for women who exercise," said Courneya. "It's really a hot bed of research right now."

The U of A in Edmonton, Alberta is one of Canada's premier teaching and research universities serving more than 30,000 students with 6,000 faculty and staff. It continues to lead the country with the most 3M Teaching Fellows, Canada's only national award recognizing teaching excellence.

Note: If no author is given, the source is cited instead.

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