Epiville

Quizzes

Quiz 1, Module Confounding

1. Education, a marker of socioeconomic status, was one of the potential confounders considered in the study of pesticide use and breast cancer in Teitelbaum et al. (2007). Please explain why education was considered to be a potential confounder:

  1. Education is associated with high exposure to pesticide use. Those with higher education may have larger homes with more lawns and gardens in need of pesticide application to enhance their landscape's appearance. Further, more advanced education is associated with a higher risk of breast cancer (hypothesized to operate via a host of factors, including older age at having a first child), and is not in the causal pathway of interest between pesticide use and breast cancer (pesticide use is not hypothesized to cause education).
  2. Education is in the causal path between pesticide use and breast cancer. All variables in the causal pathway are potential confounders regardless of their association with exposure and outcome.
  3. Although education is not associated with pesticide use, advanced education is associated with a higher risk of breast cancer (hypothesized to operate via a host of factors, including older age at having a first child). Moreover, it is not in the causal pathway of interest between pesticide use and breast cancer (pesticide use is not hypothesized to cause education).
Answer (a) — correct: For a variable to be a confounder, it must fulfill three basic properties: 1) be associated with the exposure, 2) be a risk factor for the disease, and 3) not in the causal pathway of interest. Education, a marker of socioeconomic status meets these criteria. First, it is associated with pesticide use, hypothesized to operate via home ownership and the accompanying lawn and/or garden in suburban Nassau and Suffolk counties. Second, it is a risk factor for breast cancer, possibly related to delays in child bearing, which is associated with breast cancer. Finally, it is not hypothesized to be in the causal pathway between pesticide use and cancer.
Answer (b) — incorrect: A confounder cannot be an intermediate step in the causal pathway of interest. If a third variable is in the causal pathway of interest, it is not a confounder but a mediator.
Answer (c) — incorrect: A variable must fulfill three basic properties to be considered a confounder- one, that it is associated with the exposure of interest. The remaining criteria include: a risk factor for the disease, and not in the causal pathway of interest.