Cardiorespiratory fitness could be important for reducing a man’s risk of developing and dying from certain cancers, Scandinavian research suggests.
The study in JAMA Network Open linked higher cardiorespiratory fitness with a reduced risk of dying from colon, lung, and prostate cancer—the three most common cancers in men.
Greater fitness was also associated with a reduced risk of being diagnosed with colon and lung cancer, although it was linked with raised prostate cancer diagnoses. The findings suggest that the intensity of exercise could be critical in determining how protective physical activity is against certain cancers.
In a theoretical calculation, avoiding very low cardiorespiratory fitness could have prevented 4% to 8% of all colon cancer cases, 4% of all deaths from lung cancer, and 4% to 19% of deaths from prostate cancer.
The cohort study differs from others in using maximal oxygen consumption as an objective measure of cardiorespiratory fitness, rather than simply relying on self-reported physical activity.
“Historically we have focused on the role of physical activity in reducing cancer risk, but the exciting finding from this large study is that cardiorespiratory fitness is also important in reducing a man’s risk for developing and dying from certain cancers,” explained author Kate Bolam, PhD, an exercise oncology researcher at the Swedish school of health and sport sciences in Stockholm.
“We could see a future where fitness tests are included in routine medicals to better understand individuals’ risk not only for heart disease, but also for cancer.”
The team studied data on 177,709 Swedish men who completed occupational health profile assessments from October 1982 until December 2019 and compared this with first-time cancer events and mortality data on national registries.
Health profile assessments have been carried out in Swedish health services since the 1970s and are offered free, on an optional basis, to all employees working for a company or organization connected to occupational or other health services.
During a mean follow up of 9.6 years, there were 499 incident cases of colon cancer, 283 of lung cancer, and 1918 of prostate cancer; there were also 152 deaths from colon cancer, 207 from lung cancer, and 141 from prostate cancer.
Higher cardiorespiratory fitness, determined from estimated maximal oxygen consumption on a submaximal cycle ergometer test, was associated with significantly lower risks of colon and lung cancer, with a hazard ratio (HR) of 0.98 in each case, albeit with a higher risk of prostate cancer incidence at an HR of 1.01. The latter result could be due to increased prostate cancer screening among fit men, the researchers suggest, or the important role that inherited factors play in this cancer.
Higher estimated maximal oxygen consumption was associated with a lower risk of death from colon, lung and prostate cancers, with HRs of 0.98, 0.97 and 0.95, respectively.
After adjusting for potential confounding factors, the benefits for colon cancer incidence remained for cardiorespiratory fitness that was moderate (>35-45 ml/min/kg), or high (>45 ml/min/kg) compared with very low (≤25 ml/min/kg) levels.
For prostate cancer mortality, the benefits remained for low (>25-35 ml/min/kg), moderate and high cardiovascular fitness, with corresponding HRs of 0.67, 0.57 and 0.29.
Only high cardiovascular fitness was associated with significant benefits among deaths from lung cancer, with an HR of 0.41.
Age affected the lung cancer results, and higher cardiorespiratory fitness was only associated with a lowered risk of its incidence and death in participants who were at least 60 years of age.
The researchers stress that, while physical activity and cardiovascular fitness are related, physical activity is the behavior and cardiorespiratory fitness is the physiologic response.
“It is important for the general public to understand that higher-intensity [physical activity] has greater effects on [cardiorespiratory fitness] and is likely to be more protective against the risk of developing and dying from certain cancers,” the researchers wrote.
“In addition, the results of this study are important when communicating risk levels for people without cancer who have completed exercise tests to understand that [cardiorespiratory fitness] is not only important for cardiovascular disease risk, but also cancer risk.”
