Exercise 6 Chapters 13, 14 & 15

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Exercise 6 Chapters 13, 14, & 15 (30 questions, 1 point per question) 1. What is the best measure of association to explain what percentage of the new diagnoses of disease X are explained by exposure to Y among those exposed to Y? a. Relative risk b. Risk ratio c. Odds ratio d. Attributable risk e. Incidence rate ratio 2. A politician asks an epidemiologist how many cases of coronary heart disease can be prevented if they manage to eliminate the exposure to smoking in city A. The epidemiologists explain that, if they eliminate smoking, they could prevent 22% cases of coronary heart disease. What measure of association was used to answer this question? a. Population attributable risk b. Odds ratio c. Relative risk d. Incidence rate e. Risk ratio 3. The incidence of disease X is 56/1,000 per year among smokers and 33/1,000 per year among nonsmokers. What proportion of cases of disease X are due to smoking among those who smoke? a. 23% b. 33% c. 41% 56-33/56 = 23/56 = 0.41 =41% d. 56% e. 59% 4. In a cohort study of smoking and myocardial infarction in City A, the number of myocardial infarctions were 250 cases among 7,000 smokers and the number of myocardial infarctions were 150 cases among 20,000 nonsmokers. What is the relative risk of smoking in this cohort study? a. 0.5 b. 1.7 c. 3.5 d. 4.8 e. 7.5 5. In a cohort study of smoking and myocardial infarction in City A, the number of myocardial infarctions were 250 cases among 7,000 smokers and the number of myocardial infarctions were 150 cases among 20,000 nonsmokers. What is the attributable risk (risk difference) of smoking? a. 2.8 per 1,000 b. 3.6 per 1,000 c. 7.5 per 1,000 d. 28.2 per 1,000 e. 35.7 per 1,000 6. In a cohort study of smoking and myocardial infarction in City A, the number of myocardial infarctions were 250 cases among 7,000 smokers and the number of myocardial infarctions were 150 cases among 20,000 nonsmokers. From another source, a cross-sectional study, we know that 30% of the total population in City A were smokers. What is the population proportion attributable risk of smoking in City A? a. 15% b. 30% c. 53% to find incidence in total population = (incidence in exposed) (% smokers) + (Incidence in nonexposed))(% nonsmokers) = (250/7000) (30%) +(150/20000)(70%) 1

= (35.7) (0.30) + (7.5) (0.70) = 10.71+5.25=15.96 Therefore, population proportion attributable risk = (incidence in total population - Incidence in nonexposed)/ incidence in total population = (15.96-7.5)/15.96 =8.46/15.96 0.53 = 53% d. 79% e. 90% 7. Which of the following statements is the most accurate description of the risk and relative risk of lung cancer deaths in this study? Use the following information: Lung Cancer and Coronary Health Disease Mortality by Smoking Status Age-adjusted death rates per 100,000 Smokers Nonsmokers Lung cancer 150 70 Coronary heart disease 700 300 [Modified from Doll R, Peto R. Mortality in relation to smoking: 20 years’ observations on male British doctors. Br Med J . 1976;2(6051):1525–1536.] a. The risk of lung cancer deaths is 2.1 times greater in smokers compared with nonsmokers. b. The risk of lung cancer deaths is 2.1 times less in smokers compared with nonsmokers. c. Because investigators followed up participants over 20 years, deaths rate cannot be used as a risk. d. The risk of lung cancer deaths among smokers is 70 per 100,000. e. The risk of lung cancer deaths among nonsmokers is 150 per 100,000. 8. Which of the following statements is the most accurate description of the attributable risk (deaths per 100,000) of coronary heart disease for smokers in this study? Use the following information: Lung Cancer and Coronary Health Disease Mortality by Smoking Status Age-adjusted death rates per 100,000 Smokers Nonsmokers Lung cancer 150 70 Coronary heart disease 700 300 [Modified from Doll R, Peto R. Mortality in relation to smoking: 20 years' observations on male British doctors. Br Med J . 1976;2(6051):1525–1536.] a. The attributable risk of coronary heart disease deaths is 700 deaths per 100,000. b. The attributable risk of coronary heart disease deaths is 400 deaths per 100,000. c. Attributable risk cannot be used as an indicator of the disease burden reduction that could be achieved if the risk factor eliminated. d. The risk of coronary heart disease deaths among smokers is 70 per 100,000. e. The risk of coronary heart disease deaths among nonsmokers is 30 per 100,000. 9. The following is a measure of the strength of association, typically used in case-control studies to measure the association between exposure and disease: a. Incidence rate b. Population attributable fraction c. Attributable fraction d. Prevalence 2

e. Odds ratio 10. Lack of physical activity is a known factor associated with colon cancer. However, colon cancer develops even among active individuals. Moreover, several individuals who perform very little levels of physical activity never develop colon cancer. Hence, in the causal relationship between physical inactivity and colon cancer, the lack of physical activity is a. necessary and sufficient. b. sufficient but not necessary. c. necessary but not sufficient. d. neither necessary not sufficient. e. confounded. 11. Cardiorespiratory fitness, measured as VO 2 max in mL/kg/min (maximum oxygen consumption), is associated with increased longevity. Recent evidence suggests that higher fitness increases the life span. Those with a low VO 2 max have a life expectancy after 60 years of 7 years, those with moderate VO 2 max of 15 years, and those with a high VO 2 max have a life expectancy after 60 of 23 years. Which of the causal criteria is illustrated with this example? a. Temporal relationship b. Strength of association c. Replicability of findings d. Specificity of association e. Dose-response effect 12. Temporal relationship is a necessary criterion to establish causality. Which of the following epidemiologic study design allows to evaluate temporal relationship? a. Cross-sectional b. Case-control c. Transversal d. Cohort e. Literature review 13. Which of the following statements is not evidence suggesting Exposure A as a causative agent on Disease X? a. Exposure A is clearly linked to mediator M. Approximately 11% of mediator M patients will go on to have Disease X over a 10-year period. b. Many of the observations regarding Exposure A and Disease X have been replicated repeatedly. c. Prevalence of Exposure A in patients with Disease X is 90% to 100%. d. Eradication of Exposure A heals Disease X at the same rate as other treatment of choice. e. None of above 14. Human papillomavirus (HPV) infections are known to be a cause of cervical cancer. In most cases, HPV goes away on its own and does not cause any health problems. However, the worldwide HPV prevalence in cervical carcinomas is 99.7%. This indicates that HPV-negative carcinoma is extremely uncommon. In this case, HPV is which of the following? a. A necessary and sufficient cause b. A necessary but not sufficient cause c. A sufficient but not necessary cause d. Neither necessary nor sufficient e. None of the above 15. In a hypothetical cross-sectional study, marriage was found to be strongly associated with increased levels of happiness. Authors concluded that marriage was a cause of happiness. However, a reviewer of this study argued that because it is a cross-sectional study, it could not be determined whether marriage caused happiness or happiness caused marriage. What criterion of causal relationships was not met in the study according to the reviewer? a. Strength of association 3

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b. Biologic plausibility c. Dose response d. Temporal relationship e. Replication of findings 16. Smoking participants of a cohort study are more likely to drop out. It is known that the effect of asbestos on getting cancer is much stronger among smokers. When analyzing data for this study, researchers find no association between asbestos and cancer. A potential explanation for the results of the study is a. confounding. b. effect modification. c. selection bias. d. information bias. e. specificity of association. 17. In a case-control study, a researcher found no association between exposure to A and disease B. Later she found out that there was a misclassification when measuring exposure to A, in both cases and controls. What is a potential explanation for the results (no association) of this case-control study? a. Nondifferential misclassification b. Differential misclassification c. Selection bias d. Confounding e. Effect-modification 18. Investigators think that income might be a confounder in the relationship between Hispanic ethnicity and cardiovascular disease. They conduct a case-control study, and they match cases and controls based on income. They find that Hispanics are more likely to have cardiovascular disease as compared with non-Hispanics. What is the measure of association used in such study? a. Risk ratio b. Relative risk c. Incidence rate ratio d. Attack rate e. Odds ratio 19. Investigators think that income might be a confounder in the relationship between Hispanic ethnicity and cardiovascular disease. They conduct a case-control study, and they match cases and controls based on income. They find that Hispanics are more likely to have cardiovascular disease as compared with non-Hispanics. What would you conclude about income as a potential confounder in this association? a. Income is a confounder . b. Income is not a confounder. c. Income is an effect modifier. d. Income is not associated with cardiovascular disease. e. Income is not associated with ethnicity. 20. This table shows incidence rates (per 100,000) of groups exposed to neither risk factors or to one or two risk factors for lung cancer. What is the expected value of incidence rate X on asbestos exposure group among smokers in additive scale? Incidence Rates of Lung Cancer by Asbestos and Smoking Exposure Status Smoking status No Yes 4

Asbestos exposure No 2.0 6.0 Yes 4.0 X a. 4.0 b. 6.0 c. 8.0 4+4 d. 12.0 e. 24.0 21. This table shows incidence rates (per 100,000) of groups exposed to neither risk factors or to one or two risk factors for lung cancer. What is the expected value of incidence rate X on asbestos exposure group among smokers in multiplicative scale? Incidence Rates of Lung Cancer by Asbestos and Smoking Exposure Status Smoking status No Yes Asbestos exposure No 2.0 6.0 Yes 4.0 X a. 4.0 b. 6.0 c. 8.0 d. 12.0 4*3 e. 24.0 22. Epidemiologists tried to investigate the role of factor Y in the exposure-disease relationship. They developed three tables to show the exposure-disease relationship based on the status of factor Y. In this analysis, what is the odds ratio in the overall population? Overall Case Control Exposed 1,000 500 Unexposed 200 500 Factor Y present Case Control Exposed 800 250 Unexposed 100 250 Factor Y absent Case Control Exposed 200 250 Unexposed 100 250 a. 0.5 b. 1.0 c. 2.0 d. 5.0 5

e. 8.0 23. Epidemiologists tried to investigate the role of factor Y in the exposure-disease relationship. They developed three tables to show the exposure-disease relationship based on the status of factor Y. Based on the information given, what is the role of factor Y in the exposure-disease relationship? Overall Case Control Exposed 1,000 500 Unexposed 200 500 Factor Y present Case Control Exposed 800 250 Unexposed 100 250 Factor Y absent Case Control Exposed 200 250 Unexposed 100 250 a. Factor Y is a confounder. b. Factor Y is an effect measure modifier. c. Factor Y is a mediator. d. Factor Y is an outcome. e. Factor Y does not have any role in the exposure-disease relationship. 24. Epidemiologists tried to investigate the role of factor X in the exposure-disease relationship. They developed three tables to show the exposure-disease relationship based on the status of factor X. Based on the information given, what is the role of factor X in the exposure-disease relationship? Overall Case Control Exposed 1,050 500 Unexposed 300 700 Factor X present Case Control Exposed 700 250 Unexposed 200 350 Factor X absent Case Control Exposed 350 250 Unexposed 100 350 6

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a. Factor X is a confounder. b. Factor X is an effect measure modifier. c. Factor X is a mediator. d. Factor X is an outcome. e. Factor X does not have any role in the exposure-disease relationship. (OR for OVERALL, FACTOR X Present and Factor X absent is 4.9) 25. Epidemiologists tried to investigate the role of factor Z in the exposure-disease relationship. They developed three tables to show the exposure-disease relationship based on the status of factor Z. Based on the information given, what is the role of factor Z in the exposure-disease relationship? Overall Case Control Exposed 200 160 Unexposed 200 240 Factor Z present Case Control Exposed 20 90 Unexposed 80 210 Factor Z absent Case Control Exposed 180 70 Unexposed 120 30 a. Factor Z is a confounder. b. Factor Z is an effect measure modifier. c. Factor Z is a mediator. d. Factor Z is an outcome. e. Factor Z does not have any role in the exposure-disease relationship. 26. The following table shows data describing age-standardized incidence rates for cervical and breast cancer among Irish women living in Ireland, Irish immigrants to the United States, and daughters of Irish immigrants in the United States. The rates are reported for two age categories: adult women less than 40 years of age and greater than 40 years of age. Among women less than 40 years of age, what is the relative risk for cervical cancer comparing daughters of Irish immigrants to women in Ireland? 7

a. 1.50 b. 1.55 c. 1.64 d. 2.70 e. Cannot be calculated with the information provided 27. The following table shows data describing age-standardized incidence rates for cervical and breast cancer among Irish women living in Ireland, Irish immigrants to the United States, and daughters of Irish immigrants in the United States. The rates are reported for two age categories: adult women less than 40 years of age and greater than 40 years of age. What is the proportion of cervical cancer risk in Irish women under 40 years of age that is attributable to moving to the United States? a. 12% b. 19% c. 56% d. 100% e. Cannot be calculated with the information provided 28. The following table shows data describing age-standardized incidence rates for cervical and breast cancer among Irish women living in Ireland, Irish immigrants to the United States, and daughters of Irish immigrants in the United States. The rates are reported for two age categories: adult women less than 40 years of age and greater than 40 years of age. Which cancer has a greater risk after the onset of menopause? a. Cervical b. Breast c. Both d. Neither e. Cannot be calculated with the information provided 29. The basis for the healthy worker effect is that: a. Having a job makes people healthier and less susceptible to disease b. Employment status is correlated with health status 8

c. Persons who work are less likely to be exposed to harmful agents d. Persons who work have health insurance and receive better treatment e. Studies of persons who work are confounded by socioeconomic status 30. Epidemiologists were interested in investigating the relationship between exercise and development of coronary heart disease (CHD) among women. Women ages 45 to 55 years were interviewed to determine their exercise habits at entry into the study. They were then followed for 15 years to determine the incidence of CHD in the cohort. The investigators concluded that these data demonstrate a causal relationship between exercise and subsequent CHD. Which of the Hill’s criteria best applies to this dataset? a. Biologic plausibility b. Consistency c. Specificity d. Dose-response e. None of the above 9

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Exercise 6 Chapters 13, 14 & 15

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