Associations between physical activity and cancer were also similar in subgroups of normal weight and overweight participants, and in current smokers or people who never smoked.
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But to get those benefits, researchers concluded, more is better. Overall, a higher level of physical activity was associated with a 7 percent lower risk of total cancer, the researchers found. The reduced risk ranged from 42 percent for esophageal cancer to 10 percent for breast cancer. They were 27 percent less likely to develop liver cancer, 26 percent less likely to develop lung cancer and 23 percent less likely to develop kidney cancer. And the most frequent exercisers drove their rates of myeloid leukemia down by 20 percent. The risk of developing seven cancer types was 20 percent (or more) lower among the most active participants (90th percentile of activity) as compared with the least active participants (10th percentile of activity). Myeloma and cancers of the head and neck, rectum, and bladder also showed reduced risks that were significant, but not as strong.
A separate 20 year study by academics at the University of Minnesota underlines the findings of previous research that cardiorespiratory fitness (CRF) reduces diabetes in both sexes.
She also noted the participants’ physical activity was all self-reported, which could be problematic since researchers have discovered that “people over-report their level of activity”. The latest study’s authors sought a universal method to track the level of fitness, so they used a scale from 0 to 100.
Participants were asked whether they did moderate or vigorous intensity activities in their free time, like walking, running or swimming, and how much physical activity they got.
Dr Steven Moore, epidemiologist at the National Cancer Institute in Maryland, said: “These findings support promoting physical activity as a key component of population-wide cancer prevention and control efforts”. Stomach cancer of the cardia was 22 percent lower among individuals who regularly exercised.
“This finding may help encourage those who are overweight or obese to be physically active”, Moore’s team wrote.
Two types of cancers, melanoma and prostate cancer, were higher among those who were more active.
People were classified as doing higher levels of exercise if they were in the top 10 percent of all people in their study groups for the amount of exercise they did.
The new research published online by JAMA Internal Medicine said physical inactivity is common with an estimated 31 percent worldwide not meeting recommended levels. The jury was still very much out beyond that though. The authors looked at the incidence of 26 kinds of cancer occurring in the study follow-up period, which lasted 11 years on average. Is lifelong physical activity essential, or can a middle-aged couch potato still reduce her risk by lacing up her sneakers and hitting the gym?
“Those are things that prevent cancers”.
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Exercise has all sorts of benefits, Moore said. “However, additional research, including more formal mediation analyses, on the underlying mechanisms for the recreational physical activity-cancer association should be pursued vigorously”, writes Marilie D. Gammon, Ph.D., of the University of North Carolina at Chapel Hill Gillings School of Public Health, and coauthors in a related commentary.
