Deck 13: More on Risk: Estimating the Potential for Prevention

Question 1

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
E) Odds ratio

Answer 1

E
Odds ratio is a measure of the strength of an association that is typically used in case-control studies."Population attributable fraction" and "attributable fraction" describe measures of the potential preventive effect of eliminating an exposure."Incidence rate" and "prevalence" describe measures of disease frequency.

Question 2

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

Answer 2

D
Because this study is a cohort study,the incidence rate can be considered as a risk.The risk of myocardial infarction among smokers is found by dividing 250 by 7,000.The risk of myocardial infarction among nonsmokers is found by dividing 150 by 20,000.The relative risk of myocardial infarction is 35.7 per 1,000 divided by 7.5 per 1,000,which equals 4.8.

Question 3

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

Answer 3

A
The population attributable risk is a measure that allows to calculate the proportion of cases that are due to a particular exposure in a particular population.

Question 4

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
[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.

Question 5

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%
D) 56%
E) 59%

Question 6

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

Question 7

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%
D) 79%
E) 90%

Question 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
[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.

Question 9

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