"Our results suggest that the Surgeon General's recent estimate of smoking-attributable mortality may have been an underestimate. The Surgeon General's estimate, which took into account only the 21 diseases formally established as caused by smoking, was that approximately 437,000 deaths among adults are caused each year by active smoking (not including secondhand smoke). However, the Surgeon General’s report presents an alternative estimate of 556,000 deaths among adults on the basis of the excess mortality from all causes. The difference between these two estimates is nearly 120,000 deaths.1 If, as suggested by the results in our cohort, at least half of this difference is due to associations of smoking with diseases that are causal but are not yet formally established as such, then at least 60,000 additional deaths each year among U.S. men and women may be caused by cigarette smoking."
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.