Saturday, February 9, 2013
Assignment 2: Second-hand Smoking and Lung Cancer: Cause and Effect
1. Briefly summarize the study design and results.
The study followed 91,540 married non-smoking women above the age of 40 for 14 years from 1966-79 in various districts of Japan. It tried to assess how their husbands' smoking habits affected their risk of getting lung cancer. The smoking habits of the studied husbands ranged from non-smoking to more than 20 cigarettes per day. The study considered possible confounding variables such as rural/urban homes, lifestyle habits, and individual health risks. The results for risk ratio was found to be the following: non-smoking household (1.00), ex-smoker household (1.43), and chain smokers (1.90). The study concluded that the number of smokers' wives who had a higher risk of lung cancer than the wives of non-smokers was statistically significant indicating a high correlation. The husband's smoking habits did not affect the risk of the wife developing other types of cancers but did effect her chances of getting emphysema and asthma.
2. What do you find interesting/important about this study?
This study seeks to prove the link between second-hand smoke and lung cancer, an important health hazard. If causation is proved, it changes public policy regarding smokers and also how people view smoke. Ever since studies such as this one have indicated that second-hand smoke raise the risk of lung cancer for non-smokers, many states and countries have made it illegal to smoke in public places. This study is therefore important because it decreases many people's chances of getting lung cancer. From a sociological standpoint, I find the social change caused by this study rather interesting. People now view smokers as not only harming themselves, but as harming those around them, whether it's the general public or the smoker's immediate family and they often are shunned or scolded for their bad habit.
3. What is the advantage of using this type of study design here?
The large number of subjects observed and their varying lifestyles allowed for an accurate measurement of the effects of various confounding variables like rural or urban location, drinking habits, etc. It also allowed for researchers to observe a range of non-smoking, formerly-smoking, and currently smoking husbands as well as the range for smoking from 1-20 cigarettes per day. Possible subjective bias from one spouse to the other was also eliminated by interviewing the couple separately. By having a long term study, researchers were also able to have a more accurate statistical analysis.
3. You read in Schneider (Chapter 6) about proving cause and effect. Discuss why or why not you feel the results of this study support second-hand smoke as a cause of lung cancer.
Though I believe there is definitely a cause and effect relationship between second-hand smoke and lung cancer, I do not believe that this study proves it. Though a strong correlation between second-hand smoke and lung cancer was made, correlation does not necessarily mean causation. For example, it is possible that perhaps breathing in the smoke is not what increases chances of lung cancer, it might be the lingering smell of smoke in the house or on the spouses' clothes that does damage to the lungs. The study also sought from the beginning to prove that second-hand smoke caused lung cancer. It is possible that the statistics of the study were unintentionally skewed in order to support this theory.
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I think you did a great job in adding other thoughts to what this study summarized. It is very true that, because of studies such as these, it has become illegal to smoke in public places - and also more commonly in the United States that you could have added, the smoking and non-smoking sections that are common in almost every public place from restaurants to seating areas in airports. I also liked your perspective from a sociological standpoint, since many people do share that point of view. I hadn't thought of those points myself.
ReplyDeleteWhile I see why you don't believe that causation is not exactly represented through this study, there is data and specific trends that point to lung cancer as being a result of second-hand smoke. While it may be a lingering smell or some other result from the wive's husbands' smoking, it is still a result of the husband's heavy smoking habits that contribute to lung cancer; we call it second-hand smoke but the article details on many more factors that can branch beyond only second-hand smoke. Since so many things are shared between a husband and wife (home, time, items, etc.), the lung cancer can be from something other than inhaling smoke someone else is releasing, but it still supports the general conclusion of the study which relates said causation.
I really appreciated your use of terms such as risk ratio and causation. I also thought your summary was efficient and well crafted. Good job discussing the impact of such reports as well. I do agree with Yarelix, however, that any lingering smell is still second-hand smoke. I do think, however, that the study proves a link between second hand smoke and cancer. While there are many other factors present in a couple's home, the large sample size revealed higher rates in homes where most variables were held constant except smoking habits. Therefore I think it is safe to say that smoking was effectively singled out as a major risk factor.
ReplyDeleteSally,
ReplyDeleteGreat article summary. I like your answer to the 2nd question as well. Indeed, this study did change a lot of our thinking about the dangers of smoking to the non-smokers around them.
For question 3, yes, I think this prospective study design was a good one. This is a type of randomized control trial. A case-control study is another way of studying this. In this method, the study would start with the women who already have lung cancer and investigate what might have caused that cancer.
I'm a little confused by your answer to number 4. You say there is "a cause and effect relationship" between second-hand smoking and lung cancer, but then you state you're unsure it is really a "cause". Remember Hill's criteria from your text in this situation. This is the criteria for causation we use in public health and includes several criteria like strength of association, consistency, specificity, etc. Which of these criteria does the study satisfy?
Erin
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