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