Japanese Study

Hirayama's study was designed to assess the relationship between passive smoking and the occurrence of lung cancer in the wives of smoking husbands in Japan. The study followed 91,450 wives that fit the criteria. They followed the 91,450 couples for a 14-year period between 1961 and 1974. The 91,450 women constituted %91-%99 of the target population. The study also tracked the effects of passive smoking on the occurrence of stomach cancer, emphysema, and asthma. The results showed a direct correlation between the women who were married to heavy cigarette smokers have a half to third greater chance of contracting lung cancer. The results also indicated that asthma and emphysema were higher in this cohort. There was no statistical evidence to suggest that there is a correlation between being married to a smoker and the occurrence of stomach cancer in the wife.

The scale of the study is what I think is most important. Keeping track of nearly 100,000 must have required a tremendous amount of funding and man-hours to regularly check up on that many people.  With such a large sample size, it is very hard for anyone to dispute the relationships between the passive smoking in partners and the occurrence of lung cancer in the wife. I was also surprised about the fact that wives of smokers in agricultural areas were significantly more likely to contract lung cancer than there urban counterparts. The study attributes this to the larger amount of time that couples spend together in agricultural settings, but I thought the population density and close living situation of urban centers would cause  greater harm than the extra time together.

The benefits of using a cohort study in this situation is two fold: firstly it allows for the study to follow the subjects for long periods of time, as well as being able to effectively follow large numbers in order diffuse doubters who would otherwise have concerns about the determining a relationship in a small sample size. Also, the cohort study allowed for the study to take into account other possible environmental factors that may have skewed the results of the study, such as the wives’ personal habits, living situation, and location.

I believe the study had convincing results, particularly because the study spanned through all kinds of environments. The study did not just focus on smokers in urban settings, but also rural, and agricultural settings. The study was most convincing because the relative risk values that were greater than one strongly support a relationship between lung cancer and passive smoking, with husbands who smoked twenty or more cigarettes a day. I also believe that it was important that the study interviewed the couples independently because it maximized the honesty of the responses.