2013 Study Links Fitness and Low Cancer Rates
If you need more reason to exercise, consider a recent study that shows that cardiovascular fitness in middle-aged men reduced both the likelihood of their getting cancer decades later and of their dying from it if they did get it.
The study started with 17,000 healthy men of about 45 years old who were observed at the Cooper Center Longitudinal Studies, an organization founded by Kenneth Cooper, the author of the seminal book Aerobics. The subjects were given treadmills tests to see how well they handled increases in the speed and incline of the treadmill. Then, when the same subjects were 65 years old, their earlier fitness levels were correlated to their incidence of prostate, colorectal, and lung cancer. The results were that the more fit subjects were less likely to develop these cancers and less likely to die from them.
The study adjusted for other risk factors, such as smoking and being overweight. The study conducted by Dr. Susan Lakowsky of the University of Vermont College of Medicine and was released at the annual meeting of the American Society of Clinical Oncology in May 2013.
According to Dr. Lakowsky, the key is how efficiently the body consumes oxygen. This determines how well oxygen gets to each organ. This in turn affects things that affect cancer risk, such as inflammation, hormone levels, and oxidative damage.
The subjects’ fitness levels were measured by metabolic equivalent of task (“METs”). According to Dr. Lakowsky, an average middle-aged person can get up to about 9 METs while walking fast on an inclined treadmill, while athletes can get over 15. In the study, every additional MET the subjects achieved reduced their risk of dying from cancer by 14 percent and from heart disease by 23 percent. Subjects who were most fit during their first tests were at 68% to 38% less likely to develop cancer than the least fit subjects.
Many other studies have shown that exercise lowers the risk of cancer. See, for example, physical activity and cancer risk.
What is Different About This Study
What is different about the current study is that the same subjects were studied over time, that is,“longitudinally.” Among other benefits of longitudinal studies is that they avoid the “self-reporting bias” of subjects saying how often they exercise. The current study suggests that people who are unfit in their 40s can lower their cancer risk by increasing their fitness. However, the study does not actually show that. There is a good chance that most-of the fittest subjects at the beginning of the study had been exercising consistently for many years before and after their tests. Lower incidence of cancer for these men is one thing. Getting fit late in life and expecting similar results is quite another. Thus, the study does not really show that getting fit reduces your risk of cancer. Moreover, the previous studies also compare people who exercise regularly with those who don’t. They do not compare unfit people who become fit with unfit people who don’t become fit. That would be the true test of fitness as a treatment. In the meantime, what we have is evidence of fitness as a preventative.