Smoking is considered by far the most important risk factor associated with development of, and functional decline in COPD. As well as having more respiratory symptoms, smokers also have a greater annual rate of lung function decline, as assessed by change in FEV1, and are at greater risk of premature mortality due to COPD than nonsmokers. In the Lung Health Study, middle-aged smokers who continued smoking had an accelerated loss in FEV1 compared with nonsmokers.

There is no risk-free level of exposure to tobacco smoke, and there is no safe tobacco product.

Smoking is the primary cause of preventable illness and premature death. Smoking harms every organ, causing lung cancer, respiratory disease, heart disease as well as numerous cancers in other organs including the lip, mouth, throat, pancreas, bladder, kidney, stomach, liver, blood and cervix. 50% of smokers will be killed by their addiction.