A research study observes that individuals who exercise regularly have a lower  risk of developing heart disease. However, those who work out also tend to  maintain a healthier diet, which itself lowers heart disease risk. In this scenario,  diet serves as a—?

1. A

   Mediator

2. B

   Effect modifier

3. C

   Confounder

4. D

   Independent variable

Appeared in: NORCET 10 Mains

Explanation

• A confounder is a variable that is associated with both the exposure of interest (exercise) and the outcome of interest (heart disease).
• In the given scenario, diet is linked to exercise (people who exercise tend to eat better) and is also an independent risk factor for heart disease.
• Because it influences both, it can distort the apparent relationship between exercise and heart disease, making it a classic example of a confounder.
• The variable is not on the causal pathway between the exposure and outcome (i.e., exercise does not directly cause a healthier diet).

Why Other Options Were Wrong

• Option A: A mediator explains the mechanism by which the exposure affects the outcome (e.g., Exercise -> Weight Loss -> Lower Heart Disease Risk). The scenario does not suggest that exercise causes a healthier diet.
• Option B: An effect modifier changes the magnitude of the effect of the exposure on the outcome for different groups. The scenario does not state that the effect of exercise on heart disease is different for people with different diets.
• Option D: The independent variable is the factor being manipulated or studied for its effect, which is 'exercise' in this case. Diet is a separate, additional variable.

Related Visual

Clinical Relevance

• Nursing practice connection: Knowing Identification of confounding variables in research helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
• Nurses must be able to critically appraise research to ensure they are applying valid evidence to practice. Recognizing potential confounders is a key part of this appraisal.
• When implementing a new protocol (e.g., a mobility program), nurses should consider other factors (confounders) that might be influencing patient outcomes, such as changes in medication, diet, or social support.
• What if? If the study found that exercise only reduced heart disease risk in people who also had a healthy diet, but had no effect in those with a poor diet, then diet would be an 'effect modifier', not a confounder.

How to Approach the Question

• First, identify the primary relationship being studied: the effect of the exposure (exercise) on the outcome (heart disease).
• Next, analyze the role of the third variable (diet). How does it relate to the exposure and the outcome?
• Recall the definitions of a confounder, mediator, and effect modifier.
• A confounder is associated with both the exposure and the outcome and is not on the causal pathway.
• A mediator is on the causal pathway (exposure -> mediator -> outcome).
• An effect modifier changes the relationship between the exposure and outcome.

Concept Tested & Keywords

• Concept Tested: Identification of confounding variables in research.
• Stem keywords: research study, exercise, heart disease, healthier diet
• Lead-in keywords: serves as a

Question ID

QgKLfAMll2HsvS-acnDt-E

Copy ID

Reference Book

E6 Robert Boland, Marcia L. Verduin - Kaplan and Sadock's Comprehensive Text of Psychiatry-Wolters Kluwer Health (2024) (pp 1-16525 of 16525) p. 2842-2844

E6 NursingResearch Polit 11e Part 1 p. 223-225