Researchers gave treadmill tests to 2,979 men - 1,602 who were former smokers and 1,377 who were current smokers - to assess their “cardiorespiratory” fitness, or how easily the circulatory and respiratory systems can supply oxygen to muscles during physical exertion. They assessed exercise capacity using a standard measurement known as metabolic equivalents (METs) which reflects how much oxygen is consumed during physical activity.
Researchers followed the men for an average of 11.6 years; during this period, 99 participants were diagnosed with lung cancer and 79 of these people died from cancer.
Among former smokers, each 1-MET increase during treadmill tests was associated with a 13% lower risk of developing lung cancer. Moderate to high levels of cardiorespiratory fitness were associated with a 51% to 77% lower risk of developing lung malignancies, the study found.
And among current smokers who were later diagnosed with lung cancer, each 1-met increase during treadmill tests was associated with an 18% lower risk of dying from cancer. Moderate to high levels of cardiorespiratory fitness were linked to an 84% to 85% lower risk of dying from cancer.
“Both former and current smokers can significantly reduce their risk of developing and dying from lung cancer by achieving higher cardiorespiratory fitness,” said lead study author Baruch Vainshelboim of the Veterans Affairs Palo Alto Health Care System and Stanford University in Palo Alto, California.
“Aerobic exercise at moderate to vigorous intensity such walking, jogging, running, biking, or elliptical for 20 to 30 minutes three to five times a week can improve cardiorespiratory fitness,” Vainshelboim said by email.
Lung cancer remains the most common cancer worldwide, with more than 2 million new cases and 1.8 million deaths a year, researchers note in the American Journal of Preventive Medicine. Tobacco is the single most important risk factor for developing and dying from lung cancer, accounting for up to 90% of diagnoses and more than 80% of deaths, researchers note.
Eliminating low cardiorespiratory fitness as a risk factor could prevent about 11% of lung cancer diagnoses in former smokers and roughly 22% of cancer deaths in current smokers who develop lung cancer, the study authors estimated.
While the study can’t prove whether or how improving aerobic fitness might directly reduce the odds of developing or dying from lung cancer, the results still point to one modifiable risk factor that current and former smokers might be able to control to reduce their risk, researchers conclude.
It’s possible that being more fit helps limit exposure to toxins from cigarettes in the lungs, said Trude Eid Robsahm, a researcher at the Cancer Registry of Norway, Institute of Population-based Cancer Research, who wasn’t involved in the study.
“In addition, physical activity improves activity in immune cells and produces a cancer-inhibiting environment in the tissue,” Robsahm said by email.
Getting recommended levels of exercise will help, said Dr. Sudhir Kurl, a researcher at the Institute of Public Health and Clinical Nutrition, University of Eastern Finland in Kuopio.
“The consensus public health guideline to perform 150 minutes per week of moderate-intensity physical activity such as brisk walking, jogging will move most of individuals out of the low-fitness category,” Karl, who wasn’t involved in the study, said by email. “It also may help smokers to quit smoking.”