Saturday, September 12, 2009

Smoking paradox

Do you know about smoking paradox?

I first heard of this was during a clinical round a week ago. The professor asked us about it and nobody knew the answer. He told us the answer. It was noted that the incidence of in-stent stenosis following PCI was lower in smokers than non-smoker. He explained that by activation of CYP450 by smoking. This enzyme is responsible for transformation of clopidogrel to its active form. This lowers in-stent thrombosis and also lowered clopidogrel resistance.

However I have done my own search on the web to know more about that topic. I found some additional information. There are more explanations not mentioned by our professor. One explanation is the younger age of smokers in the studies revealing that paradox. Another one is the relectunce of smokers toseek medical advice when such problems occur. However, the long term mortality is still higher in smokers despite this claimed paradox.

I found two other paradoxes related to smoking. One was the lower mortality of somkers hospitalized for heart failure in OPIMIZE-HF study compared with non-smokers. However, the age of the smokers in the study was also younger, and this may be a resonable explanation. Another explanation is the difference in drug handling by smokers due to enzyme induction and inhibition. The third paradox related to smoking was noted in the study of lung cancer. It was noted the Japanese population has lower incidence of lung cancer compared with western populations, despite the higher incidence of smoking in the Japanese. This time the explanations were multiple. The main explanations were genetic difference, the different cigarette types and different filters, and the more healthy lifestyles led by the Japanese (less fat and less alcohol consumption).

The term "Paradox" may be deceiving or misleading. It gives the false impression that smoking is benfitial in this disease. The fact is exactly the opposite. Smoking causes the disease process to happen in an earlier age. And the real cause for the paradox is the younger age of the smokers, not the smoking itself, I guess. However it is still established that nonsmokers have longer and more healthy lives.

If you would like to read in more details follow these links:
1, 2 and 3.

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