Exercise linked to reduced risk of several cancers

Physical activity has been associated with lower risk of heart disease and all cause mortality, but its association with risk of cancer is not well understood.

Moore et al research published in JAMA Internal Medicine, suggests that exercise is a powerful cancer-preventive and found that physical activity drove down the rates of a broad array of cancers even among smokers, former smokers, the overweight and obese.

Researchers collected data from 12 prospective studies from the United States and Europe and analyzed associations between self-reported physical activities with the incidence of 26 types of cancer in the study period, which lasted 11 years between 1987 and 2004.

A total of 1.44 million participants (median [range] age, 59 [19-98] years; 57% female) and 186 932 cancers were included. High versus low levels of physical activity were associated with lower risk of 13 cancers: esophageal adenocarcinoma, liver, lung, kidney, gastric, endometrial, myeloid leukemia, myeloma, colon, head and neck, rectal, bladder, and breast. The data indicated that a higher level of activity was tied to a 7 percent lower risk of developing any type of cancer. Individuals who were very active had a 20% lower risk of cancers of the esophagus, lung, kidney, stomach, endometrium compared with people who were less active.  The reduction was slightly lower for colon, bladder, and breast cancers.

Body mass index adjustment modestly attenuated associations for several cancers, but 10 of 13 inverse associations remained statistically significant after this adjustment. Leisure-time physical activity was associated with higher risks of malignant melanoma and prostate cancer.  Associations were generally similar between overweight/obese and normal-weight individuals. Smoking status modified the association for lung cancer but not other smoking-related cancers.

Health care professionals should emphasize that physical activity was associated with lower risks of many cancer types and most of these associations were evident regardless of body size or smoking history.

Cancers linked to Obesity

Obesity is a major contributor to the development of cancer.  According to the National Cancer Institute obesity is associated with increased risks for cancer of the esophagus, pancreas, colon and rectum, breast (after menopause), endometrium, kidney, thyroid, and gallbladder.

 

NHANES 2007-2008 survey found 68 percent of the U.S. adults age 20 years and older are overweight or obese and 17 percent of children and teens ages 2 to 19, are obese.  According to NCI Surveillance, Epidemiology, and End Results (SEER) data, it is estimated that in 2007 in the United States, about 34,000 new cases of cancer in men (4 percent) and 50,500 in women (7 percent) were due to obesity.

In 2003, Calle et al published in NEJM the results of a study of more than 900,000 healthy adults that were followed for 16 years.  The study authors concluded that excess fat could account for 14% of all deaths from cancer in men and 20% of those in women.

A recent study of 92,834 British women enrolled in a database for cancer screening, Fourkala et al reported in an article published in BMJ Open that women who go up a skirt size every decade between their 20s and their 60s are at increased risk of postmenopausal breast cancer.  They also found that “an increase of one size every 10 years led to a 33 percent rise in the risk of postmenopausal breast cancer, while an increase of two sizes per decade led to a 77 percent rise in risk.

Bhaskaran et al study of 5.2 million adults that was published in Lancet found that 166 955 individuals developed cancer and that body-mass index (BMI) was associated with 17 of 22 cancers.  Although the effects varied substantially by site, increase in BMI was roughly linearly associated with cancers of the uterus, gallbladder, kidney, cervix, and leukemia.  BMI increase was positively associated with liver, colon, ovarian, and postmenopausal breast cancers overall. They estimated inverse associations with prostate and premenopausal breast cancer risk, both overall and in non-smokers. By contrast, for lung and oral cavity cancer, they observed no association in non-smokers.  Assuming causality, 41% of uterine and 10% or more of gallbladder, kidney, liver, and colon cancers could be attributable to excess weight. They conclude that extra weight could contribute to more than 12,000 cases of cancer in the UK population every year.

Related Resources:

Physical Activity and Cancer

Energy balance: Weight and Obesity, PhysicalActivity, Diet