Sleep, Physical Activity and the Prevention of Breast Cancer

Although there is a growing amount of evidence that regular physical activity has benefits for cancer prevention, a new study recently presented at the American Association for Cancer Research's International Conference on Frontiers in Cancer Prevention Research, by James McClain, has suggested that this benefit can be maximised by sleeping at least seven hours per night.

 

The authors initiated the study based on the observation that short duration sleep seemed to counteract the hormonal and metabolic benefits of physical activity. They reviewed data on almost 5968 women who completed surveys in 1998 about how much physical activity and sleep they typically get. Nine years later, the study group had 604 new cases of cancer, including 186 cases of breast cancer.

The study found that the half of women who participated in the higher level of physical activity had an 80% drop in overall cancer risk and a 75% reduction in breast cancer risk. However, of the more physically active women, those under the age of 65 who slept less than seven hours a night had a 1.5-fold increase in risk for developing cancer which suggests that lack of sleep offsets the benefits of physical activity.

These findings lead to the suggestion that the combination of physical activity and a good-nights sleep work combination to provide an additional benefit compared to one or the other on their own in terms of their benefit on cancer.

Professor John Boyages, from the Westmead Breast Cancer Institute, pointed out that “it is important to keep in mind that although the risk of breast cancer in younger women is not as high as their older counterparts, these findings may be important for quite a lot of women. It’s also important to keep in mind the fact that regular exercise has well established benefits in terms of cancer prevention”.

The next step, suggest the authors, is to confirm these findings and gain an understanding of just how these effects are occurring; although, at this stage it is believed that physical activity's effects on factors including hormone levels, immune function, and body weight may play an important role.

“Apart from the benefits on metabolism, physical activity is well known to be important in preventing obesity. Being overweight itself has been well established as being one of the modifiable risk factors for breast cancer” added Kellie Bilinski, a research dietitian at the Westmead Breast Cancer Institute. “For instance, a recent study showed that women who gained about 10 kg or more since menopause were at an 18 percent increased risk of breast cancer.1 Whereas, those who lost about 10 kg or more since menopause (and kept the weight off) and who had never used postmenopausal hormones were at a 57 percent lower risk of breast cancer than those who simply maintained their weight.”

Another factor that has gained attention lately is the role of vitamin D in breast cancer development. Some researchers have suggested vitamin D deficiency and insufficiency is reaching epidemic proportions, particularly in those who avoid the sun, have dark skin or increased requirements such as elderly people. Vitamin D is believed to have a role in preventing the growth of tumours so it’s possible that inadequate levels of vitamin D contribute to tumour development. “While research is growing in this area, the significance of vitamin D in breast cancer development and prognosis is still not well established. We are currently looking at this in the research we are conducting at the Breast Cancer Institute” added Ms Bilinski. “Studies like these really highlight the importance for women to try and plan their day so that they get some regular activity in attempt to avoid weight gain both before and after menopause, get adequate sleep, and sunshine in moderate amounts without getting burnt.”

Reference List 

Eliassen AH, Colditz GA, Rosner B, Willett WC, Hankinson SE. Adult weight change and risk of postmenopausal breast cancer. JAMA 2006; 296(2):193-201.

American Association for Cancer Research Seventh Annual International Conference on Frontiers in Cancer Prevention Research, Washington, D.C., Nov. 16-18, 2008. James McClain, PhD, MPH, cancer prevention fellow, National Cancer Institute.

Last Updated on Monday, 08 February 2010 16:08