LETTER TO THE EDITOR
Reply
Ron T. van Domburg, MD, PhDa
a University Hospital Rotterdam Dijkzig and, Erasmus University, Thoraxcenter, Location 5 Midden, Room H553, Dr. Molewaterplein 40, 3015 GD Rotterdam, The Netherlands
vandomburg{at}thch.azr.nl
We appreciate the comments of Dr. Shander regarding our recent article in JACC (1). In his comments he concluded that "the best chances of survival are among those who smoke up until the time of their surgery and then quit rather than never to smoke at all." We have proven that patients who quit smoking after bypass surgery are significantly better off than those who continue to smoke. However, in our study we only compared the patients who quit smoking with patients who continued smoking. Because of its irrelevancy, we did not compare the patients who quit smoking with patients who did not smoke. Furthermore, we did not use the term "never smoked" but used the term "nonsmoking." We did not distinguish between patients who have never smoked and ex-smokers (patients who had stopped smoking before the time of surgery), and we combined these two groups into one nonsmokers’ group at the time of surgery. The smoking habits at the time of surgery did not influence survival during the follow-up period. This smoker’s paradox is partly explained by the difference in baseline characteristics such as an age difference (smokers were four years younger than nonsmokers). Another explanation could be selection bias, as many smokers tend to die of fatal myocardial infarctions before they have the chance to undergo coronary bypass surgery (2).
Finally, the survival rates of the nonsmokers were probably positively influenced by the ex-smokers. In conclusion, the worse condition of the nonsmokers as compared with the smokers at the time of surgery largely explains the survival differences between nonsmokers and patients who quit smoking.
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References
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1. van Domburg RT, Meeter K, van Berkel TFM, Veldkamp RF, van Herwerden LA, Bogers AJJC. Smoking cessation reduces mortality after coronary artery bypass surgery: a 20-year follow-up study. J Am Coll Cardiol. 2000;36:878–883[Abstract/Free Full Text]
2. Schatzkin A, Cupples LA, Heeren T, Morelock S, Kannel WB. Sudden death in the Framingham Heart Study. Differences in incidence and risk factors by sex and coronary disease status. Am J Epidemiol. 1984;120:888–899[Abstract/Free Full Text]
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