Putting It Together: Passive Smoke The following abstract appears in The New England

Chapter 1, Problem 23

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Putting It Together: Passive Smoke? 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 includinginformation on exposure to environmental tobacco smokewere compiled and analyzed. Exposure was measured interms of smoker-years, determined by multiplying thenumber of years in each residence by the number of smokersin the household. RESULTS. Household exposure to 25 or more smoker-yearsduring childhood and adolescence doubled the risk of lungcancer. Approximately 15 percent of the control subjects whohad never smoked reported this level of exposure. Householdexposure of less than 25 smoker-years during childhood andadolescence did not increase the risk of lung cancer. Exposureto a spouses smoking, which constituted less than one thirdof total household exposure on average, was not associatedwith an increase in risk. CONCLUSIONS. The possibility of recall bias and othermethodologic problems may influence the results of casecontrolstudies of environmental tobacco smoke. Nonetheless,our findings regarding exposure during early life suggest thatapproximately 17 percent of lung cancers among nonsmokerscan be attributed to high levels of exposure to cigarettesmoke during childhood and adolescence. (a) What is the research objective? (b) What makes this study a case-control study? Why is thisa retrospective study? (c) What is the response variable in the study? Is itqualitative or quantitative? (d) What is the explanatory variable in the study? Is itqualitative or quantitative? (e) Can you identify any lurking variables that may haveaffected this study? (f ) What is the conclusion of the study? Can we concludethat exposure to smoke in the household causes lungcancer? (g) Would it be possible to design an experiment to answerthe research question in part (a)? Explain.