What do your lungs have in common with your gut? Would you believe poor cardiovascular fitness could increase your chances of developing cancer in both? One study found an interesting link between these types of cancer and cardiovascular health.
A recent study investigated the connection between cardiovascular fitness and cancers of the lung and bowel. Researchers found people who scored best on an exercise stress test had the lowest lung and bowel cancer rates on a 7-year follow-up. They also had the highest survival rates among participants who did develop those forms of cancer.
Studying the Connections
One recent study examined 49,143 patients who had undergone exercise stress tests. The patients were all cancer-free at the beginning of the study, and their ages ranged from 40 to 70 years, with the average age being around 54. Women comprised 46% of participants, with a racial diversity of 64% white, 29% black and 1% Hispanic. The researchers followed up an average of 7 years after the initial tests.
Researchers noted the participants' cardiorespiratory fitness (CRF), which is a measure of peak energy expenditure. CRF was determined by age, physical activity, organ health and other factors. The researchers used data from the Henry Ford Cancer Institute tumor registry to see which of the participants developed cancer during that period. They also used the Social Security Death Master File to determine the causes of any participants' deaths.
Adjusting for age, body mass index, medication use, smoking history and other factors, researchers found patients with the best cardiovascular fitness were 77% less likely to develop lung cancer and 61% less likely to develop colon cancer. When patients with good CRF did develop cancer, they were 44% less likely to die of lung cancer and 89% less likely to die of colon cancer.
To ensure they weren't confusing cause and effect, the researchers adjusted their analyses to account for the possibility that undetected cases of cancer could have been present during the stress tests, affecting their outcomes. These “sensitivity analyses” only affected findings by a handful of percentage points. This means that, even if some rogue cases of undetected cancer affected the study, it's safe to assume the researcher's findings were still sound.
The study did have some limitations. Researchers couldn't adjust for all participant's diets and alcohol consumption, menopausal status or use of hormone therapy, and notable diversity in lung health was lacking among the black racial group. There was also no way of tracking lung health during the time between the initial stress tests and the follow-up.
More research may be needed to clarify this seeming connection. One possible explanation is that the side effects of physical fitness—better respiratory function, more effective immune function, improved bowel habits and reduced inflammation—play a role. Those with higher fitness levels were also less likely to be smokers, which may be a factor in some cases of lung cancer.
Regardless of the exact connection, we do know the better shape we're in, the better shape our lungs will also be in, so we should all get moving!
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