Examkin

Question

Difficulty: MediumBias, Confounding, and Validity

A group of investigators is designing a case-control study to evaluate the potential association between a diet high in processed meats and the development of colorectal cancer. During the planning phase, the researchers identify regular physical activity as a major concern. Physical activity is known to be associated with both a lower intake of processed meats and a decreased risk of colorectal cancer, and it is not considered to lie on the causal pathway between the two. The researchers want to ensure that their study findings are not distorted by this variable. Which of the following methodological strategies can be appropriately utilized to control for the effect of physical activity in this study? (Select all that apply)

  1. Matching participants based on physical activity levels during the recruitment phaseAnswer
  2. B
    Reporting stratum-specific odds ratios to demonstrate how physical activity alters the magnitude of the diet's effect on cancer risk
  3. Incorporating physical activity as a covariate in a multivariable logistic regression model during data analysisAnswer
  4. D
    Using a Chi-square test to adjust for baseline differences in physical activity between the case and control groups
  5. E
    Calculating the positive predictive value of the diet for colorectal cancer across different levels of physical activity

Answer

Matching participants based on physical activity levels during the recruitment phase AND Incorporating physical activity as a covariate in a multivariable logistic regression model.
Controlling for confounding can be effectively achieved either during the design phase of a study (via matching, restriction, or randomization) or during the analysis phase (via multivariable regression or stratified analysis to calculate a pooled Mantel-Haenszel estimate). Matching ensures that cases and controls have an identical distribution of the confounder, neutralizing its distortion. Multivariable logistic regression adjusts for the confounder mathematically by evaluating it alongside the primary exposure, allowing researchers to isolate the exposure's independent association with the outcome.

Step-by-Step Solution

1
Identify the role of the third variable (physical activity) in the scenario.
Physical activity is associated with both the exposure and the outcome and is not on the causal pathway. Therefore, it is a confounding variable.
Understanding the epidemiological definition of the variable dictates the methodological strategies required.
2
Determine which options represent valid methods to control for a confounder during the design phase.
Matching is a valid design-phase strategy to equalize the confounder's distribution between groups.
Confounding must be addressed proactively during study design or retroactively during data analysis.
3
Determine which options represent valid methods to control for a confounder during the analysis phase.
Multivariable logistic regression is a valid analysis-phase strategy to mathematically adjust for the confounder.
If confounding was not entirely prevented in the study design, it can still be isolated and removed using appropriate statistical modeling.

Key Concept

Methods for controlling confounding in observational studies (Matching in design phase; Multivariable regression in analysis phase)
Rate this question

Topics

Bias, Confounding, and Validity

More questions from this topic