Friday, February 8, 2013

Blog Assignment 2 - Smoking and Lung Cancer

This week’s blog assignment, we read an article by Takeshi Hirayama titled Non-smoking Wives of Heavy Smokers Have A Higher Risk of Lung Cancer: A Study From Japan. It outlines the relationship between smoking and lung cancer, dealing with second hand smoke in particular. The experiment studied non-smoking women aged 40 and above and their risk of developing lung cancer based on their husbands’ smoking habits. These adults were followed by “establishing a record linkage system between the risk-factor records, a residence list obtained by yearly census, and death certificates”. Not so surprisingly, the results of the experiment were that the wives of heavy smokers were more at risk of getting lung cancer than wives of non-smokers and that this relationship was significant in agricultural families. The alcohol drinking habits of these husbands proved to have no effect on the wives developing lung cancer. Finally, the article talks about passive smoking versus direct smoking and their effects. The experiment showed that there was a significant relation between how much the husbands smoked and the death of their wives from lung cancer. In addition, the study proved that the effects of passive smoking were one half to one third of direct smoking.

I found it interesting that the study looked at alcohol consumption habits of the husbands as well and compared the results with the smoking habits. It seems that the results would clearly not be similar to each other because the two habits are very different when it comes to affecting the wife’s risk to getting lung cancer. However, it is possible that using the results from the husband’s alcohol consumption habits clearly support and help prove the claim that smoking habits of the husband affect his wife’s risk of developing lung cancer the most.

In this experiment, thousands of adults, 40 years of age or younger, were followed by various methods. The study followed these adults “by establishing a record linkage system between the risk-factor records, a residence list obtained by special yearly census, and death certificates” (183). By designing the study in this way, the leaders of the experiment are able to set their own parameters and change it up when needed. In addition, the experiment divided up the different variables, which made it easier to see the obvious differences in results. With the variables separated, it is less likely to have conflicting variables, meaning that the variables would not affect each other in the experiment.

The results of this study clearly support second-hand smoke as a cause of lung cancer. When comparing husbands’ smoking habits with the risk of developing lung cancer in their non-smoking wives, there seemed to be a huge relation between the two. The specific results from the experiment show this relation. In addition, it is important to note that the same relationship was followed, but instead of smoking habits, the husbands’ drinking habits were used. This results of this experiment showed that the husbands’ drinking habits had little to no effect on their wives’ risk of developing lung cancer. Therefore, it is clear that the results of this study support the claim that second-hand smoke can be a huge cause of lung cancer.


  1. I like the way you summarized the article so that the layperson could understand the results of the study. I would only add in some of the measurements such as p-values used in order to back your summary. Otherwise, nice work.

  2. Thanks for your post!

    For decades, public health advocates have attempted to link cigarette smoking and lung cancer. The attempt to make a causative link between smoking and lung cancer has been stymied by the long timespan prior to the development of lung cancer, the relative rarity of the disease and the numerous confounding factors that are concurrent in individuals who smoke. This landmark prospective cohort study sought to show an association between second-hand (aka side-stream) smoke exposure, lung cancer incidence, overall mortality and lung cancer attributable mortality. For more information about criteria of causation please see the Bradford Hill criteria:

    The study designers utilized a cohort design in order to analyze the risk associated with second hand smoke exposure (risk ratio = relative risk). Cohort studies are often difficult to accomplish due to the length of follow-up time, the overall cost of the study and the possibility of a large number of study participants to be lost to follow-up. In contrast, case-control studies identify cases (those with disease) and controls (those similar but without disease) and attempt to distinguish different rates of past exposure. This study sought to prove that smoke exposure was specifically related to an increase in lung cancer incidence, environment of residence is not a confounder of this relationship and that smoke exposure and lung cancer incidence has a dose response relationship (more smoke exposure causes more cancer). The authors further point out that considering their results, future comparisons of the health status between smokers and nonsmokers should control for the secondhand smoke exposure of nonsmokers.

    As you point out, the study sought to compare the association of husband smoking, other husband behavior and the lung cancer related mortality of their wives. Admittedly the downside to using a cohort analysis (taking a group and following them) is that you cannot control for all exposures. Ideally you would like to take a group of individuals and randomly exposure them to the agent of interest (here smoking) or placebo and see if there is any difference in the risk of developing the outcome (here lung cancer). For many hazardous exposures, this type of randomized control trial is unethical and/or not feasible. In this study the investigators are attempting to show that there is something unique to a particular husband behavior (smoking vs. alcohol use) that is causing an increase in lung cancer mortality. This goes to the distinction between showing an association between two things and then taking the next step toward proving causation. Which of the Hill criteria mentioned above do you think this study addresses?

  3. Smoking is injurious for health it may cause lung cancer. For more detail see my blog Lung Cancer Symptoms