Non-smokers is not an independent group!

In this blog post, I will be discussing the effect that smoking husbands have on the development of lung cancer for their non-smoking wives.  I will be summarizing a study done in Japan regarding this subject.

This study was a Cohort study that interviewed and followed 122,261 men and 142,857 women age 40 years and above.  The population was separated into non-smoking wives of smoking husbands and non-smoking wives of non-smoking husbands.  The objective of this study was to determine whether wives of smokers have an increased risk of lung cancer development.  The results showed that 346 women deaths occurred during the 14 year follow up period.  174 of these women were non-smoking women who were married to smoking husbands.  The results yielded a two tailed p-value of 0.00097, which means that the null hypothesis is rejected in favor of the alternative hypothesis since the results are statistically significant because it was not the result of chance.  In this case, the null hypothesis was that non-smoking women of smoking husbands and non-smoking women of non-smoking husbands have the same chance of developing lung cancer.  Since the p-value, 2*0.00097 < alpha (0.05 most of the time), we will accept the alternative hypothesis, which, in this case, was that non-smoking women of smoking husbands have a greater chance of developing lung cancer than non-smoking women of non-smoking husbands.  The study also concluded that husbands' smoking and alcohol drinking habits have no effect of their non-smoking wives' risk of developing other types of major cancers other than lung cancer.  Also, the effect of passive smoking was compared with the effect of direct smoking, yielding a relative risk of developing lung cancer by passive smoking of 1.8 compared to a relative risk of 3.8 for direct smokers.  Therefore, the study showed a dose-response relationship between passive smoking and the risk of developing lung cancer.  

The advantage of this study is that it allowed the examination of multiple outcomes of non-smoking wives of smoking husbands.  For instance, the study showed a relation between husbands' smoking habits and deaths from emphysema and asthma in their wives.  Also, the study found that the risk of developing other types of cancer, such as stomach and cervical cancer, in non-smoking wives did not increase with smoking husbands.  In my opinion, second hand smoking is an environmental health issue because when the primary smoker exhales the smoke, this smoke is inhaled by people who are standing within the vicinity of the primary smoker.  Therefore, these people will inhale these bad chemicals and toxics, including carcinogens, and increase their chances of developing lung cancer, since the above study has showed a dose-response relationship between passive smoking and lung cancer.  Since these toxic chemicals exhaled by the primary smoker permeates the environment and affects all of those around the primary smoker, a smoke-free environment is needed to protect people from second hand smoking.  Therefore, second hand smoking is an environmental problem because toxic chemicals are released into the air.  Although association does not always imply causation, I believe that the results of this study support second hand smoking as a cause of lung cancer.  The results from the study concluded a dose-response relationship between second hand smoking and the development of lung cancer.  Although most dose-response relationships have a safe amount of dose one can take before experiencing an adverse response, cancer does not have this safe threshold.  Therefore, the chance of developing cancer is linearly proportional to amount of dose taken by the subject.  Thus, the more dose of carcinogen taken, the greater the chance you might develop cancer.  So in this case, the more toxics inhaled by a second hand smoker, the greater the chance that person will develop lung cancer.