91Ó°ÊÓ

The following abstract appears in The New England Journal of Medicine: BACKGROUND. The relation between passive smoking and lung cancer is of great public health importance. Some previous studies have suggested that exposure to environmental tobacco smoke in the household can cause lung cancer, but others have found no effect. Smoking by the spouse has been the most commonly used measure of this exposure. METHODS. In order to determine whether lung cancer is associated with exposure to tobacco smoke within the household, we conducted a case-control study of 191 patients with lung cancer who had never smoked and an equal number of persons without lung cancer who had never smoked. Lifetime residential histories including information on exposure to environmental tobacco smoke were compiled and analyzed. Exposure was measured in terms of "smokeryears," determined by multiplying the number of years in each residence by the number of smokers in the household. RESULTS. Household exposure to 25 or more smoker-years during childhood and adolescence doubled the risk of lung cancer. Approximately 15 percent of the control subjects who had never smoked reported this level of exposure. Household exposure of less than 25 smoker-years during childhood and adolescence did not increase the risk of lung cancer. Exposure to a spouse's smoking, which constituted less than one third of total household exposure on average, was not associated with an increase in risk. CONCLUSIONS. The possibility of recall bias and other methodologic problems may influence the results of casecontrol studies of environmental tobacco smoke. Nonetheless, our findings regarding exposure during early life suggest that approximately 17 percent of lung cancers among nonsmokers can be attributed to high levels of exposure to cigarette smoke during childhood and adolescence. (a) What is the research objective? (b) What makes this study a case-control study? Why is this a retrospective study? (c) What is the response variable in the study? Is it qualitative or quantitative? (d) What is the explanatory variable in the study? Is it qualitative or quantitative? (e) Can you identify any lurking variables that may have affected this study? (f) What is the conclusion of the study? Can we conclude that exposure to smoke in the household causes lung cancer? (g) Would it be possible to design an experiment to answer the research question in part (a)? Explain.

Step by step solution

01

Understanding the Research Objective

The research objective of the study is to determine whether lung cancer is associated with exposure to environmental tobacco smoke within the household.

02

Defining a Case-Control Study and Retrospective Study

This study is a case-control study because it compares 191 patients with lung cancer (cases) to an equal number of persons without lung cancer (controls), where both groups have never smoked. It is retrospective because it looks back at the exposure histories of the subjects rather than following them forward in time.

03

Identifying the Response Variable

The response variable in this study is the occurrence of lung cancer. This is a qualitative variable as it categorizes individuals based on whether they have lung cancer or not.

04

Identifying the Explanatory Variable

The explanatory variable is the level of exposure to environmental tobacco smoke within the household, measured in 'smoker-years'. This is a quantitative variable, as it quantifies exposure over time.

05

Identifying Lurking Variables

Possible lurking variables could include genetic predisposition to lung cancer, occupational exposures to other carcinogens, overall air quality in the household environments, and lifestyle factors like diet and exercise.

06

Stating the Conclusion and Assessing Causality

The study concludes that high levels of exposure (25 or more 'smoker-years') during childhood and adolescence double the risk of lung cancer among nonsmokers. However, the conclusions caution that recall bias and other methodological problems might influence the results. Therefore, we cannot definitively conclude that exposure to smoke in the household causes lung cancer; we can only suggest an association.

07

Possibility of Designing an Experiment

Designing a controlled experiment to answer the research question would be ethically impossible because it would require deliberately exposing individuals to tobacco smoke to observe the development of lung cancer. Therefore, observational studies, including case-control or cohort studies, are the only feasible approaches to address this research question.

Unlock Step-by-Step Solutions & Ace Your Exams!

• Full Textbook Solutions

  Get detailed explanations and key concepts

• Unlimited Al creation

  Al flashcards, explanations, exams and more...

• Ads-free access

  To over 500 millions flashcards

• Money-back guarantee

  We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!

Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Research Objective

The research objective of this study is to examine if lung cancer is linked to exposure to environmental tobacco smoke within the household. This is vital as understanding such a relationship can guide public health policies to minimize exposure and potentially reduce lung cancer incidence. To break it down, the study seeks to answer a specific question: Does being around smokers at home increase the chances of developing lung cancer for nonsmokers?

Retrospective Study

This study is classified as a retrospective case-control study. 'Retrospective' means looking back in time. Here, researchers looked at the past exposure histories of individuals. They compared two groups:

• 191 patients with lung cancer (cases) who never smoked
• An equal number of persons without lung cancer (controls) who also never smoked

The researchers then analyzed these histories to identify any correlation between past exposure to tobacco smoke and lung cancer development.

Response Variable

In this study, the response variable is whether the individual has lung cancer. This is a qualitative variable as it categorizes individuals into two groups: those with lung cancer and those without. Qualitative variables provide categorical outcomes and in this context, are used to determine the health status related to lung cancer.

Explanatory Variable

The explanatory variable here is the level of exposure to environmental tobacco smoke within the household. This exposure is measured in 'smoker-years,' a quantitative measure calculated by multiplying the number of years spent in each residence by the number of smokers in the household. Quantitative variables are used here to quantify the extent of exposure over time and evaluate its potential impact on lung cancer risk.

Lurking Variables

Lurking variables are factors not accounted for in the study that might influence the results. In this study, several lurking variables could affect the outcomes:

• Genetic predisposition to lung cancer
• Exposure to other carcinogens (e.g., at work)
• Overall air quality in household environments
• Lifestyle factors, such as diet and exercise habits

These factors might confound the association between household tobacco exposure and lung cancer risk.

Study Conclusion

The study concludes that high levels of exposure (25 or more 'smoker-years') during childhood and adolescence double the risk of lung cancer among nonsmokers. However, the study also acknowledges that recall bias and other methodological issues could affect results. As such, even though there's an observed association, one cannot definitively claim that household smoke exposure causes lung cancer, only that there appears to be a significant link.

Experiment Design

Designing an experiment to directly answer the research question would be ethically challenging. A controlled experiment would involve exposing individuals to tobacco smoke intentionally, which is not acceptable. Hence, observational studies, like the one discussed (case-control or cohort studies), are the only feasible ways to explore such questions ethically. These studies observe subjects without intervening, gathering data over time or retrospectively to find patterns and associations.