Many people know the risks of smoking, and many people know the risks of being over-weight, but not many studies have looked at the mortality risk of the two factors together. As expected, there was an elevated mortality risk that was higher than the risk of any of the two factors by themselves. The research paper’s design was very good in standards of following the requirements of the information needed in a retrospective cohort. The sample size that was used was large >80,000. Of those, over 64,000 were women. Researchers made sure to remove any people that had a history of prior cancer or myocardial infarction (MI). They used a questionnaire to ascertain the exposed and non-exposed groups. Some of the factors looked at in the questionnaire was height, weight, alcohol use, and smoking habits, among other things.
Body mass index (BMI) and smoking status were both stratified to see how the two factors affect mortality risk. The causality of the two factors were very clear in the results that where concluded. It was found that there was a 3.5 to 5 fold increase in all-cause mortality of smokers that were very obese (BMI > 35). In contrast if you where just very obese and did not smoke your Relative Risk (RR) for all-cause mortality was lower (1.4—2.5). The strongest cause and effects found in this study was that of smoking and very obese women who had a 6-11 fold increase in circulatory disease mortality.
In looking at the data I did not see any mistakes in the correlations that were drawn. The confidence intervals used in the study ranged from .005-.0001 so they are definitely in the realm of scientific creditability. Some of the areas that could prove a problem is the fact that the people in the study filled out the questionnaire themselves, and people could have been dishonest about weight or height, which could have made the calculation on BMI skewed to the left, meaning a lower BMI than what they actually are. I think this because most people say they weigh less then they do. Also, there is a problem with the former smokers if they started to smoke again after the survey. Their mortality information should have been with the smokers instead of the non/former smokers.
In all, I think the information obtained from this study is an important find for policy makers, in where money should go in preventative health care, and to which of the sexes should it be focused on more (female). By using this information correctly policy makers can maximize the amount of lives saved.
D. Michal Freedman. (2006). The Mortality Risk of Smoking and Obesity Combined. American Journal of Preventive Medicine, 31(5) 355-362