Demographic variables that differed among conditions were included as covariates in subsequent analyses. (jamanetwork.com)
These analyses will account for covariates such as family history of atopy and infants» diet and will be assessed over the first year of life by a survival analysis approach.48, 49 Thus, this prospective design will also allow us to disentangle the relative contributions of genetic and nutritional aspects, as will statistical path analyses to test for a potential mediating effect of PUFA levels among genotypes and AD development.50 (bmjopen.bmj.com)
While selection bias is still a concern, it is worthwhile noting that the authors control for a very rich set of covariates including student demographics, parental income, parental education, student AFQT score, freshman year GPA, state of birth and various school characteristics. (educationnext.org)