A novel strategy to address unmeasured confounding when comparing opioid agonist therapies in pregnancy

Abstract

Opioid addiction in pregnancy is a growing concern that has recently received a lot of attention. When comparing recommended opioid agonist therapies, many currently published studies guiding practice may be impacted by unmeasured confounding by indication. Populations of women who receive methadone are generally different from those treated with buprenorphine. Women treated with methadone frequently have more severe and uncontrolled addiction compared with buprenorphine treated patients; however, these factors are typically unmeasured or unavailable in large observational data sets. Consequently, findings of superior perinatal outcomes with buprenorphine may in truth be a result of an overall healthier profile of women taking this medication. In this issue of the American Journal of Epidemiology, Brogly et al. describes an approach utilizing detailed data from an External Cohort (n = 113) to account for confounding by indication in a larger Medicaid population (n = 1,020) to more accurately compare opioid agonist therapies in pregnancy. Authors found that the decreased risk of preterm birth and infant length of hospitalization associated with buprenorphine compared with methadone were attenuated after accounting for the additional confounding. These authors should be commended for providing a novel method to address this bias in future studies.