Furthermore, we took advantage ofthe family-based design of the SYS cohort and showed that—in sister-sister pairs discordant for maternal smoking during pregnancy—theexposed sisters had lower V1 surface area than the non-exposed ones
How much does comparing sisters actually strengthen the evidence that maternal smoking is responsible for a smaller V1 surface area given other confounding environmental and genetic factors that impact siblings?
Nonetheless, several prenatal con-founders (e.g. alcohol, drugs, paternal smoking) were not included inthe phenotypic modeling due to their limited measurements in theUKB cohort;
How might controlling for these other confounding variables impact the results of the study? What might a study on paternal and secondhand smoking look like given this studies results?
maternal education
How did the researchers define maternal education? And did they control for other possible confounding factors like maternal age or socioeconomic status? How might other variable impact the results of the study?