In a cohort study the relative risk for chronic obstructive pulmonary disease (C
ID: 3183720 • Letter: I
Question
In a cohort study the relative risk for chronic obstructive pulmonary disease (COPD) for moderate smokers versus non-smokers was 4. For heavy smokers compared to non-smokers the relative risk was 10.What would have been the relative risk for COPD in this study if the heavy smokers were used as the reference category? explain your answer.
A) this cannot be calculated with the available data
B) for non-smoking 0.1 and for moderate smoking 0.4
C) for non-smoking 0.2 and for moderate smoking 0.6
D) for non-smoking 4 and for heavy smoking 10
Explanation / Answer
1.
RR w.r.t Heavy Smokers of non-smokers
= 1/ (RR w.r.t Heavy Smokers of non-smokers )
RR w.r.t Heavy Smokers of non-smokers = 10
=1/ 10
=0.1
2.
RR w.r.t Heavy Smokers of Mod-smokers
= 1/ (RR w.r.t Heavy Smokers of Mod-smokers )
RR w.r.t Mod Smokers of Non Smokers smokers = 4
RR w.r.t Heavy Smokers of non-smokers = 10
=
RR w.r.t Mod Smokers of Non Smokers smokers /RR w.r.t Heavy Smokers of non-smokers
=4/10
=0.40
Answer is therefore, B