Coffee Drinking and CAD Assignment
1. There is growing interest in whether inflammation is important in the pathogenesis of coronary artery disease (CAD) and whether the presence of certain inflammatory diseases outside of the heart can influence the risk of development of CAD. Specifically, there is interest in the role of periodontal disease. To address this, a cohort study was performed to evaluate the independent association between periodontal disease (inflammation of the gums and other soft tissue in the mouth) and the occurrence of CAD. The unadjusted (crude) analysis found that those persons with periodontal disease at baseline have a higher rate of CAD than persons without periodontal disease. Coffee Drinking and CAD Assignment Help Assessment of plasma level of C-reactive protein (CRP) was also performed at baseline. CRP level is known to be elevated in many inflammatory conditions and has also been associated with the development of coronary artery disease. In this cohort study, after adjustment for CRP level, the association between periodontal disease and coronary artery disease was no longer present.
Using causal diagrams (DAGs) as described in class, diagram two possible scenarios that could explain why adjustment for CRP resulted in you no longer seeing an effect for periodontal disease. Coffee Drinking and CAD Assignment Help
Non-smokers
Smokers
CAD
No CAD
CAD
No CAD
High coffee
40
90
High coffee
150
65
Low coffee
65
150
Low coffee
45
20
(a) Calculate the crude odds ratio (for the association of coffee drinking and CAD) and the two stratum-specific odds ratios. Show your calculations. (3 pts) Coffee Drinking and CAD Assignment Help
(b) Next assess whether:
i. smoking is related to coffee consumption among those without CAD.
ii. smoking is related to CAD among subjects with low coffee consumption
Show the new 2×2 tables for these relationships and your calculations for the stratum specific ORs for the new tables. (4 pts)
(c) If you knew nothing else about this clinical/biological system, are the data given in the question and your calculations in item (b) sufficient evidence for you to conclude that smoking is a confounder in the relationship between coffee use and CAD? Explain the rational behind your answer. APA Style
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