Bicycle Network: Prevention

The Cancer Council in Australia says: 'Being physically active probably reduces the risk of cancer of the breast (especially in post-menopausal women)'.

The Cancer Council says: In Australia, being physically inactive ranks second only to tobacco smoking in terms of adding to the cancer burden from different known risk factors.7 Recent Australian data suggests that physical inactivity accounts for 5.6% of the total cancer burden and 6.6% of the total burden of disease. (7)
The International Agency for Research on Cancer (IARC) estimates that 14% of all cases of colon cancer and 11% of post-menopausal breast cancers are attributable to physical inactivity. (8)

From the Cancer Council's Position Statement on Physical Activity and Cancer Prevention

See the full document

A systematic review in 2007 found there was strong evidence for an inverse association between leisure time physical activity and post-menopausal breast cancer with risk reductions ranging from 20% to 80% among cohort and case-control studies.(11)

However the evidence was much weaker for pre-menopausal breast cancer.(11)

Evidence for a dose-response effect was observed in about half the higher quality studies that reported a decreased breast cancer risk.(11)

A trend analysis among case-control studies revealed that each additional hour of physical activity per week decreased the risk of breast cancer (all types) by 6%.(11)

While duration of physical activity (hours/week) was the primary exposure measure in the review, some studies also reported metabolic intensity (MET).(11)

Three out of four cohort studies found that higher MET hours/week was associated with a lower risk of breast cancer, and one study was statistically significant.(11)

This was also seen in case-control studies, with three out of four showing breast cancer risk was reduced with higher MET hours/week, and one study was statistically significant.(11)

In 2003, a systematic review examining health behaviours in early adulthood found that case-control studies appear to show a weak link between physical activity in early life (i.e. adolescence) and risk of breast cancer (both pre- and post-menopausal), although no relationship was seen in two out of three cohort studies.(12)

However these results only reflect a particular life stage (i.e. adolescence) and it is likely that the accumulation of physical activity over many years is important for cancer protection. Overall, epidemiological studies suggest that being physically active probably reduces the risk of breast cancer, especially in post-menopausal women.(5)
 

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Position statement: Physical activity and cancer prevention 9
Approved Public Health Committee – March 2009, update August 2009
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7. Begg S, Vos T, Barker B, Stevenson C, Stanley L, Lopez A. The burden of disease and injury in Australia 2003. Canberra, AIHW. 2007.
8. International Agency for Research on Cancer. Weight control and physical activity. Volume 6. Lyon: IARC. 2002.