Saturday, February 9, 2013

Non-Smoking Wives of Heavy Smokers

The effects of second hand smoking have been proven to be highly dangerous in various studies. Cigarette smoke includes many toxic substances that reach even people who don’t smoke so it makes sense that many of the non-smokers associated with heavy smokers are affected by these substances. Takeshi Hirayama decided to study the effect of husbands smoking on the risk of lung cancer in their non-smoking wives. 29 health centre districts in Japan interviewed and followed 265,118 adults over 40 years old to study the consequences of several health risk factors like alcohol and cigarettes on health. During 14 years of follow up, it was found that out of 346 lung cancer related deaths, 174 of the deaths were of non-smoking wives.

Results showed that heavy smoking in husbands did not have much effect on the non-smoking wives’ risk of developing some cancers like stomach or cervix cancer, but the risks of getting illnesses like emphysema and asthma were higher among the same wives. There seemed to be no correlation between other health risk factors like alcoholism and the risk of non-smoking wives getting lung cancer. Surprisingly, the data gathered also showed that non-smoking wives of heavy smokers who work in agriculture was higher than with husbands who do not work in agriculture. Most importantly, the results showed that non-smoking wives of heavy smokers did in fact have a higher risk of developing lung cancer than wives of non-smokers.

I found it really interesting that agriculture and location of a family became such an important variable in the course of the experiment. Since the study was focused on smoking in non-smoking wives, I expected variables that could be easily matched with smoking like whether the type of smoking involved was passive or direct. It amazed me that during the course of an experiment, variables like agriculture and whether a family is urban or rural were noticed. It made sense in the end that since wives of husbands who work in agriculture spend more time with their husbands, their risks for getting lung cancer was higher than in the wives of husbands who do not work in agriculture. The same logic applies to why non-smoking wives of heavy smokers in rural families have a higher risk of getting lung cancer than those in urban families.

The study design Takeshi Hirayama used included interviewing and following a population and recording data using a record linkage system. This study design made it possible for the Hirayama to have a high representation in his study. With a high representation, he is able to generalize his results to larger populations and that make his results more reliable. Since his results are reliable, more people are likely to take the results of his study seriously. In using a record linkage system, Hirayama was able to gather data in a more convenient manner. Also, a record linkage system make it easier to put data from different sources together and since the data was gathered from 29 different health centers, it made the results more united.

The results of this study do support second-hand smoke as a cause of lung cancer for many reasons. First of all, this study included a large population and that makes the results more valid than if the population was small. Also, there is a strong association already between smoking and lung cancer. The smoke from cigarettes contains toxic substances like carcinogens that have been proven to be involved in causing cancer. Even if non-smokers do not smoke, just inhaling the smoke raises their risk of cancer. Another reason that study supports second-hand smoke as a cause of lung cancer is that the results of this experiment are consistent with other experiments of this nature. There have been many studies that draw the same conclusions that Hirayama does. Even the American Cancer Society's website states clearly that secondhand smoke causes cancer.

2 comments:

  1. Good analytical framework of the article. There are a few things to note. The association with asthma and emphysema, while seen, was not statistically significant.

    Qn 3 is really asking if you notice that this is a cohort study. And what the advantages of a cohort study are. In the study, wives exposed to second hand smoke were followed and observed for an outcome (lung cancer).
    The advantages of cohort studies include the ability to look at different outcomes from a single exposure. In this case, stomach and cervical cancer were other outcomes assessed. This study design also allows a temporal relationship between exposure and outcome.

    Qn 4 is assessing your understanding of Hill's criteria for causation which you explored correctly. Don't forget the other criteria like temporality, dose-response relationship

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  2. Causes of smoking people addicted to smoking lose their appetite
    for food and energy for power.Smoking also pollutes the envirnment and the air.
    Besides it causes irritation in the eye, offends the nose and unsettles the mind.


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