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Question 1

Several studies have found that approximately 85% of cases of lung cancer are due to cigarette smoking. This measure is an example of :

Correct Answer: An attributable risk

Question 2

The results of a 10-year cohort study of smoking and coronary heart disease (CHD) are shown below:

The incidence of CHD in smokers that can be attributed to smoking is :

Correct Answer:

The correct answer is 27.5 per 1,000

Attributable risk = incidence rate in the exposed – incidence rate in the nonexposed (See page 231)

Incidence rate among smokers = 65 cases/2,000 population at risk x 1000= 32.5 per 1,000

Incidence rate among nonsmokers = 20 cases/4,000 population at risk x 1000 = 5 per 1,000

32.5 per 1,000 – 5 per 1,000 = 27.5 per 1,000 27.5 cases of CHD per 1,000 population are due to smoking

Question 3

The results of a 10-year cohort study of smoking and coronary heart disease (CHD) are shown below:

The proportion of the total incidence of CHD in smokers that is attributable to smoking is:

Correct Answer:

The correct answer is 84.6% See page 231 Formula 12-2

The proportion of the incidence in the total population = (( incidence in exposed group – incidence in nonexposed group)/incidence in exposed group )x 100

Incidence rate among smokers = 65 cases/2,000 population at risk x 1000= 32.5 per 1,000

Incidence rate among nonsmokers = 20 cases/4,000 population at risk x 1000 = 5 per 1,000

(32.5 per 1000 – 5 per 1000)/ 32.5 per 1000 = 84.6%

Question 4

In a cohort study of smoking and lung cancer, the incidence of lung cancer among smokers was found to be 9/1,000 and the incidence among nonsmokers was 1/1,000. From another source we know that 45% of the total population were smokers.

The incidence of lung cancer attributable to smoking in the total population is:

Correct Answer:

The correct answer is 3.6 per 1,000

The incidence in the total population = incidence in smokers (%smokers in population ) + (incidence in nonsmokers) (% nonsmokers in the population) = 9 per 1,000 (.45) + (1 per 1,000) (.55) = 4.05 per 1,000+ 0.55 per 1,000 = 4.60 per 1,000

Attributable risk = incidence in total population- incidence in non exposed group = 4.60 per 1,000 – 1 per 1,000 = 3.6 per 1,000

Question 5

In a cohort study of smoking and lung cancer, the incidence of lung cancer among smokers was found to be 9/1,000 and the incidence among nonsmokers was 1/1,000. From another source we know that 45% of the total population were smokers.

The proportion of the risk in the total population that is attributable to smoking is:

Correct Answer:

The correct answer is 78.3 % Page 233 Formula 12-4

The proportion of the incidence in the total population attributable to the exposure =( ((incidence in total population ) –(incidence in nonexposed group) )/ incidence in total population )x 100 = (4.6 per 1,000 – 1 per 1,000)/ 4.6 per 1,000 = 78.3%