In a case-control study of the relationship between myocardial infarction (MI) a

Question

In a case-control study of the relationship between myocardial infarction (MI) and recent oral contraceptive (OC) use, Shapiro et al. reported the following data: 29 OC users with MI; 205 non-OC users with MI; 135 OC users with no MI; 1607 non-OC users with no MI. The correct interpretation of this odds ratio (OC use is the exposure) is: A. OC users are 1.57 times more likely to have myocardial infarction than non-OC users B. OC users are 8.41 times more likely to have myocardial infarction than non-OC users. C. OC users are .32 times more likely to have myocardial infarction than non-OC users. D. OC users are 1.68 times more likely to have myocardial infarction than non-OC users.

Explanation / Answer

29 OC users have MI and 135 OC users have no MI.

So, proportion of OC users having MI = 29 / (29 + 135)

= 29 / 164 = 0.1768.

205 non-OC users have MI and 1607 non-OC users have no MI.

So, proportion of non-OC users having MI = 205 / (205 + 1607)

= 0.1131.

So, OC-users are (0.1768 / 0.1131) = 1.57 times more likely to

have MI than non-OC users.

Hence, Option (A) is the correct choice. (Ans).

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