"The 2014 Surgeon General's report estimates that cigarette smoking causes more than 480,000 deaths each year in the United States.1 This widely cited estimate of the mortality burden of smoking may be an underestimate, because it considers deaths only from the 21 diseases that have been formally established as caused by smoking (12 types of cancer, 6 categories of cardiovascular disease, diabetes, chronic obstructive pulmonary disease [COPD], and pneumonia including influenza). Associations between smoking and the 30 most common causes of death in the United Kingdom in the Million Women Study suggest that the excess mortality observed among current smokers cannot be fully explained by these 21 diseases.2

Source

Brian D. Carter, M.P.H., Christian C. Abnet, Ph.D., et al., "Smoking and Mortality — Beyond Established Causes," New England Journal of Medicine, Feb 12, 2015;372:631-40.