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

• In research, a confounder is a third variable that is associated with both the exposure (the factor being studied, e.g., exercise) and the outcome (e.g., heart disease).
• Diet fits this definition because it is independently associated with heart disease (the outcome) and is also associated with exercise habits (the exposure).
• The presence of a confounder can create a spurious or distorted association, making it seem like the exposure has a stronger or weaker effect than it actually does.
• To get an accurate estimate of the effect of exercise, researchers must statistically control for the confounding effect of diet.

Why Other Options Were Wrong

• Option A: A mediator is a variable that lies on the causal pathway between the exposure and the outcome. It explains how the exposure leads to the outcome. Diet is not caused by exercise in this scenario.
• Option B: An effect modifier changes the strength or direction of the association between exposure and 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 primary independent variable (or exposure) is the factor being investigated for its effect on the outcome. In this study, exercise is the independent variable.

Related Visual

Clinical Relevance

• Nursing practice connection: Knowing Identifying Confounding Variables in Research helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
• Understanding confounding is critical when interpreting the results of observational studies in healthcare. Many reported associations (e.g., coffee drinking and cancer) are later found to be due to confounding variables (e.g., smoking).
• Nurses reading research to inform their practice must be able to identify potential confounders to critically appraise the evidence and avoid implementing changes based on flawed conclusions.
• In clinical trials, randomization is the best method to control for both known and unknown confounders, ensuring that the groups being compared are as similar as possible.

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). Ask three questions: 1. Is it associated with the exposure? (Yes, exercisers have better diets). 2. Is it an independent cause of the outcome? (Yes, diet affects heart disease risk). 3. Is it on the causal pathway from exposure to outcome? (No, exercise doesn't necessarily cause the better diet).
• A 'yes' to the first two questions and a 'no' to the third points directly to a confounding variable.
• Review the definitions of mediator (on the causal pathway) and effect modifier (changes the relationship) to confirm they do not fit the scenario.

Concept Tested & Keywords

• Concept Tested: Identifying Confounding Variables in Research
• Stem keywords: research study, exercise, heart disease, healthier diet
• Lead-in keywords: serves as a
• Negative lead-in flag: false

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) pp. 2842-2844, 2841-2843