Question 2: (Epidemiology)

We conducted a case-control study to investigate a possible positive association between drinking diet soda and kidney disease. We selected our cases from patients hospitalized for kidney disease. We selected our controls from other hospitalized individuals who were diagnosed with obesity-related conditions. Obesity-related conditions have been shown to be positively associated with drinking diet soda.

By selecting these controls, will we likely overestimate or underestimate the true association between drinking diet soda and kidney disease? Or will this control selection have no impact? Justify your answer.

Hint: Draw the confounding triangle and then the 2x2 table for your exposure and outcome. Think about how each cell might be affected by the selection of these controls and what that would do to your calculation of excess risk.

Question 3:

In a previous problem set, we explored exposure to airborne pesticides and the risk of acute respiratory infection (ARI) among workers in a manufacturing plant in Kentucky. We conducted a one-year cohort study, but we were concerned that smoking might be masking the true relationship between pesticide exposure and ARI development.

Following the study, we confirmed the following: (1) SmokingisariskfactorforARIdevelopment (2) Becausemoremalesworkinthepesticide-exposedareaandsmokingprevalenceishigheramongmales

than among females in Kentucky, smoking is associated with pesticide exposure in our study (3) SmokingisnotonthecausalpathwaybetweenpesticideexposureandARIdevelopment

To deal with potential confounding by smoking, we have stratified the results of our analysis. Use these stratified results to answer the following:

1. a) Is smoking a confounder in the association between pesticides and the risk of ARI in our study. Justify your answer with the appropriate calculations.

2. b) Would our results be over- or underestimated if we fail to account for the confounding effect of smoking in our study? Explain in 1-2 sentences.

Non-smokers:

	ARI	NO ARI
High Pesticide	3	31
Low pesticide	7	73

Smokers:

	ARI	NO ARI
High Pesticide	19	39
Low Pesticide	7	15