Age-adjusted incidence rates per 1,000 person-years Disease Nonsmokers Smokers T
ID: 120147 • Letter: A
Question
Age-adjusted incidence rates per 1,000 person-years
Disease
Nonsmokers
Smokers
Total population
Oral cancer
2.8
5.6
3.4
Bladder cancer
7.4
15.6
8.3
Stroke
14.6
15.9
15.2
Accidents
11.4
12.3
12.0
All causes
25.6
33.4
28.7
What type(s) of study design was/were employed in these studies? Explain your answer.
What percentage of cases due to stroke would have been prevented if no one in this population smoked cigarettes?
What is the risk of oral cancer in smokers relative to nonsmokers?
What is the rate of cases due to bladder cancer among smokers that can be attributed to their smoking?
Age-adjusted incidence rates per 1,000 person-years
Disease
Nonsmokers
Smokers
Total population
Oral cancer
2.8
5.6
3.4
Bladder cancer
7.4
15.6
8.3
Stroke
14.6
15.9
15.2
Accidents
11.4
12.3
12.0
All causes
25.6
33.4
28.7
Explanation / Answer
Case control study design was employed in these studies because a case control study design compares patients who have a disease or outcome of interest( cases) with patients who do not have the diseases or outcome( control ) and looks back retrospectively to compare how frequently the exposure to a risk factor is presented in each group to determine the relationship between the risk factor and the disease.
What percentage of cases due to stroke would have been prevented if no one in this population smoked cigarettes?
for smokers it is 15.9 and for non smokers it is 14.6 do if no one would have smoked then,
difference= 15.9-14.6
= 1.3 per 1000 person
= (1.3/1000)* 100
= 0.13% of cases of strokes would have been prevented if no one in the population would have smoked.
What is the risk of oral cancer in smokers relative to nonsmokers?
risk of oral cancer in smokers = 5.6
and in non smokes = 2.8
relative risk = 5.6/2.8
= 2
i.e. smokers have twice the amount of risk of having an oral cancer as compared to non smokers,
What is the rate of cases due to bladder cancer among smokers that can be attributed to their smoking?
In smokers = 15.6
in non smokers = 7.4
rate of cases due to smoking= 15.6-7.4
= 8.2
i.e. 8.2 cases of bladder cancer per 1000 is because of smoking.