People who meet the recommended levels of leisure-time physical activity may have a reduced risk for seven types of cancer, according to a new analysis involving more than 750,000 adults.
The findings, published in the Journal of Clinical Oncology, show that several cancer types even exhibit a ‘dose/response’ relationship, meaning the higher the activity levels, the lower the risk.
The study was led by researchers at the National Cancer Institute, the American Cancer Society, and the Harvard T.H. Chan School of Public Health.
Updated guidelines for activity now state that people should aim for 2.5 to 5 hours per week of moderate-intensity activity or 1.25 to 2.5 hours/week of vigorous activity.
Moderate-intensity activities are those that get you moving fast enough or strenuously enough to burn off three to six times as much energy per minute as sitting quietly. This may include dancing, gardening or brisk walking — activities that burn 3 to 6 METs (metabolic equivalents).
METs are commonly used to express the intensity of physical activities. MET is the ratio of a person’s working metabolic rate relative to their resting metabolic rate, according to the World Health Organization.
Vigorous-intensity activities, such as running, aerobics or fast swimming, burn more than 6 METs.
For the current analysis, the researchers analyzed data from nine study groups with self-reported leisure-time physical activity and follow-up for cancer incidence. They looked for any links between physical activity levels and the incidence of 15 types of cancer.
They discovered that engaging in recommended amounts of activity (7.5 to 15 MET hours/week) was associated with a statistically significant reduced risk for seven of the 15 cancer types studied, with the reduction increasing with more MET hours.
Specifically, physical activity was linked to a lower risk of colon cancer in men (8% for 7.5 MET hours/week; 14% for 15 MET hours/week), female breast cancer (6%-10%), endometrial cancer (10%-18%), kidney cancer (11%-17%), myeloma (14%-19%), liver cancer (18%-27%), and non-Hodgkin lymphoma (11%-18% in women). The dose response was linear in shape for half of the associations and nonlinear for the others.
The analysis had some limitations: Patient numbers were limited for some types of cancer; participants were primarily white; there was a limited number of study groups with detailed physical activity measures; and the authors relied on self-reported physical activity.
“Physical activity guidelines have largely been based on their impact on chronic diseases like cardiovascular disease and diabetes,” said Alpa Patel, Ph.D., senior scientific director of epidemiology research at the American Cancer Society. “These data provide strong support that these recommended levels are important to cancer prevention, as well.”
Source: American Cancer Society