Three studies were conducted to look at the association between radon exposure (

Question

Three studies were conducted to look at the association between radon exposure (vs not exposed) and Parkinsons disease. The crude odds ratios (OR) and OR stratified by smoking status are presented in the table below: Which scenario best describes the results of Study #1 in the table above a. No interaction (effect modification) nor confounding is present b. Confounding by smoking is present c. Effect modification by smoking is present d. Confounding and effect modification are present. Which scenario best describes the results of study #2 in the table above a. No interaction (effect modification) nor confounding is present b. Confounding by smoking is present c. Effect modification by smoking is present d. Confounding and effect modification are present. Which scenario best describes the results of Study #3 in the table above a. No interaction (effect modification) nor confounding is present b. Confounding by smoking is present c. Effect modification by smoking

Explanation / Answer

Odds Ratio Interpretation

Risk Ratio

The risk ratio of something happening is where you compare the odds for two groups against each other. Risk ratio is usually reported as a percentage but you’ll also see it written as “x times more likely” (i.e. ten times more likely). If A and B are two groups. Then, Risk ratio of A is

          

                               Risk ratio of A = (OR of A) / (OR of A +OR of B)

Thus, Risk ratio of study

Crude OR

Risk Ratio

OR among Smokers

Risk Ratio

OR among Non-Smokers

Risk Ratio

Study 1

2.2

0.6875

1.4

0.5833

2.9

0.7436

Study 2

3

0.75

1.03

0.5074

1.05

0.5122

Study 3

1.8

0.6429

0.9

0.4737

3.2

0.7619

(44)

Option - C

  Effect modification by smoking is present, because OR and Risk ratio is vary in each conditions.

(45)

Option - A

  No interaction (effect modification) nor confounding is present, because, OR and Risk ratio shows that near about equal effect in smoker and non- smoker.

(46)

Option - D

Confounding and effect modification are present, because OR and Risk ratio values of each case are much differences.

(47)

Option - C

  Radon exposure is a productive factor for Parkinson’s disease, because OR values are close to 1 and Risk ratio are close to 0.5. So, that these condition are productive factor for Parkinson’s disease.

Crude OR

Risk Ratio

OR among Smokers

Risk Ratio

OR among Non-Smokers

Risk Ratio

Study 1

2.2

0.6875

1.4

0.5833

2.9

0.7436

Study 2

3

0.75

1.03

0.5074

1.05

0.5122

Study 3

1.8

0.6429

0.9

0.4737

3.2

0.7619

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