A recent study set out to investigate the association between smoking and the de
ID: 3150800 • Letter: A
Question
A recent study set out to investigate the association between smoking and the development of coronary artery disease (CAD), the leading cause of heart attacks among adults in the US. Upon enrollment in the study, 1,232 adult participants were asked to report whether they had ever smoked more than one pack of cigarettes in the lifetimes. The participants were then examined for the development of CAD once a year for the following twenty years. Examinations found 106 cases of CAD among the 368 participants who had never smoked and 419 cases of CAD among the 864 participants who had ever smoked.
1) What type of study design was used? Explain.
2) Set up the 2X2 contingency table for the data.
3) For this type of study design, what is the appropriate measure to describe the strength of the association between exposure and disease?
4) Calculate the measure identified in question 3.
5) Interpret the measure calculated in question 4
Explanation / Answer
A recent study set out to investigate the association between smoking and the development of coronary artery disease (CAD), the leading cause of heart attacks among adults in the US. Upon enrolment in the study, 1,232 adult participants were asked to report whether they had ever smoked more than one pack of cigarettes in the lifetimes. The participants were then examined for the development of CAD once a year for the following twenty years. Examinations found 106 cases of CAD among the 368 participants who had never smoked and 419 cases of CAD among the 864 participants who had ever smoked.
1) What type of study design was used? Explain.
For this study, the study design is used as case control study - Observational analytical study design.
2) Set up the 2X2 contingency table for the data.
The 2X2 contingency table for the data is given as below:
Never smoke
smoke
Total
CAD
106
419
525
Not CAD
262
445
707
Total
368
864
1232
3) For this type of study design, what is the appropriate measure to describe the strength of the association between exposure and disease?
Here, the appropriate measure to describe the strength of the association between the exposure and disease is odds ratio.
4) Calculate the measure identified in question 3.
The formula for odds ratio is given as below:
Odds ratio = (a/c)/(b/d)
Odds ratio = (106/262)/(419/445) = 0.429685
5) interpret the measure calculated in question 4
Here, we get the odds ratio as 0.429685 which is less than 1, so we interpret that there is negative association exists between the exposure and disease. An odd of exposure in cases is less than odds of exposure in controls.
Never smoke
smoke
Total
CAD
106
419
525
Not CAD
262
445
707
Total
368
864
1232
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