SOURCES: Susan Lakoski, M.D., assistant professor, medicine, University of Vermont, Burlington, Vt.; Alpa Patel, Ph.D., strategic director, Cancer Prevention Study, American Cancer Society; March 26, 2015, JAMA Oncology, online
THURSDAY, March 26, 2015 (HealthDay News) -- Fit middle-aged men appear less likely to develop lung and colon cancer in later life than their out-of-shape peers. And if they do develop cancer, they are more likely to beat it, a new study suggests.
Nearly 14,000 men underwent treadmill tests at midlife and had their medical records reviewed at age 65 or older. Researchers found that the fitter guys had roughly half the risk for lung and colon cancer compared with unfit men. Their risk for death from these cancers was about one-third lower.
"Men who are physically fit are expected to have lower levels of [cancer-related] sex hormones, enhanced immunity and lower inflammation," said lead researcher Dr. Susan Lakoski, an assistant professor of medicine at the University of Vermont.
"These effects may act together to inhibit cancer as well as risk of dying from cancer or heart disease," she said.
The researchers were surprised that the risk for developing prostate cancer wasn't lower for the fitter guys, however.
It's possible that fit men are more likely to have frequent prostate screenings and, therefore, greater opportunity to be diagnosed with prostate cancer, Lakoski explained.
"Importantly, fit men who developed prostate cancer in the current study had a lower risk of dying of cancer or cardiovascular disease," she said. "This speaks to the importance of being fit in midlife to improve survival, even if a man ultimately develops lung, prostate or colorectal cancer."
Lakoski stressed that this study, known as the Cooper Center Longitudinal Study (CCLS), shows an association between fitness and protection from cancer, not necessarily a cause-and-effect relationship.
"Future studies are needed to test these results across all major cancers in men and women, and also address how much an individual must change their fitness to see cancer prevention benefit," she said.
Evidence is growing that lifestyle behaviors influence cancer diagnoses years or decades later, the researchers said in background notes. While the link between fitness and heart protection is well-established, less is known about the connection between heart fitness and cancer, they said.
Their report was published March 26 online in JAMA Oncology.
The findings didn't surprise Alpa Patel, an epidemiologist with the American Cancer Society.
"What they found is consistent with what we know -- that physical fitness is important in cancer prevention," Patel said.
Using a patient's level of heart fitness may be a good indicator of both cancer risk and heart disease risk, she said.
Patel expects that physical fitness would also have a protective effect for women, especially for breast cancer.
She added that the reduction in lung cancer was most likely due to not smoking. Thirty-one percent of less fit men smoked, compared with only 9 percent of the most fit men, she pointed out.
For the study, Lakoski's team used information from two sources: fitness assessments conducted between 1971 and 2009 when the men averaged 49 years, and Medicare data (on men from age 65 on) from 1999 to 2009.
Over an average of 6.5 years of follow-up, 1,310 of the nearly 14,000 men were diagnosed with prostate cancer, 200 with lung cancer and 181 men with colon cancer.
The fittest men had a 55 percent lower risk of lung cancer and a 44 percent lower risk of colon cancer, compared with unfit guys, the study found.
They also had a 32 percent lower risk of dying if they did develop lung, colon or prostate cancer, the researchers said.
For more on cancer and exercise, visit the U.S. National Cancer Institute.