Does Physical Exercise have a link with Breast Density?


A strong risk factor for breast cancer in woman is the breast density and exercise has so far been considered an effective prevention against the disease. However, one of the latest studies has released that there is actually no association between physical activity and breast density.

It is estimated that women having breasts with more than 75% mammographic density have 4 to 6 times higher risk of getting the disease than those with a density lower than 25%. Women diagnosed with breast cancer may usually be advised to do physical exercises regularly to lower the risk by approximately 10 to 30 percent. Previous researches looking at a possible association between exercises and breast density, though, have been inconclusive.


The newest detailed research conducted by lead researcher Shadi Azam, from the University of Southern Denmark, and colleagues, in a large scale, has disclosed a few days ago that there is no link between the two. The researchers implied that the protective effect of exercises on breast cancer might be through other mechanisms than breast density.

The results were collected from an analysis of the physical activity of more than 5,700 pre- and post-menopausal Danish women participating in breast screening between 1991 and 2001 and those who formed part of the Danish prospective Diet, Cancer and Health study group. The researchers collected data on leisure, transport and occupation-related physical activities. The data on occupation-related physical activities was then further divided into groups including sedentary, standing, manual, and heavy manual activity.

“We know that breast density is one of the strongest risk factors for breast cancer risk. Women with high density breasts – more than 75% mammographic density – have a four to six times’ higher risk of developing the disease than do those women with a breast density of lower than 25%,” Ms. Azam said in a conference.

“This is because increased breast density reduces the sensitivity of mammograms and makes it is far more difficult to spot small tumors. It is also because breast density per se can lead to an increased risk of most of the cellular abnormalities that lead to breast cancer,” she explained.

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The results show that in the study, 56.3 percent had mixed or dense breasts, 47.5 percent played sports, 70.1 percent cycled, 52.2 percent did gardening and 92.7 percent walked.

After adjusting for other potential risk factors, the researchers found that the link noted before, between participation in sports and cycling with the odds of having denser breasts, was no longer significant. Ms. Azam also added that they found no big differences in breast density from walking or gardening.

“In the light of our findings, we believe that further studies should now be focused on other mechanisms that might explain the association between physical activity and breast cancer risk,” said Ms. Azam.

“We would be very interested to see our research replicated in another large study group in order to provide further certainty,” she expressed her expectation.

If a woman is concerned about her risk of breast cancer, she is highly recommended to eat more fruits and vegetables, consume less red and processed meats, sweets, full-fat dairy and alcohol rather than only increasing exercises.

“This is a very interesting new insight into the relationship between breast density and breast cancer risk. One might expect that undertaking physical activity and hence reducing BMI and fatty tissue would increase breast density, but this study shows that this is not the case. Untangling these complex associations will help not only determine whether extra screening is required for some women, but also aid us in refining preventive strategies,” said Professor Fatima Cardoso, Director of the Breast Unit of the Champalimaud Clinical Centre in Lisbon, Portugal.



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