title: Highlighting differences between conditional and unconditional quantile regression approaches through an application to assess medication adherence.
abstract: The quantile regression (QR) framework provides a pragmatic approach in understanding the differential impacts of covariates along the distribution of an outcome. However, the QR framework that has pervaded the applied economics literature is based on the conditional quantile regression method. It is used to assess the impact of a covariate on a quantile of the outcome conditional on specific values of other covariates. In most cases, conditional quantile regression may generate results that are often not generalizable or interpretable in a policy or population context. In contrast, the unconditional quantile regression method provides more interpretable results as it marginalizes the effect over the distributions of other covariates in the model. In this paper, the differences between these two regression frameworks are highlighted, both conceptually and econometrically. Additionally, using real-world claims data from a large US health insurer, alternative QR frameworks are implemented to assess the differential impacts of covariates along the distribution of medication adherence among elderly patients with Alzheimer's disease.
authors.affiliation: College of Medicine and Division of Health Care Policy and Research, Mayo Clinic, Rochester, Minnesota 55905, USA. borah.bijan@mayo.edu
authors.forename: Bijan J
authors.initials: BJ
authors.lastname: Borah
authors.forename: Anirban
authors.initials: A
authors.lastname: Basu
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000544:Alzheimer Disease / Q000188:drug therapy / Q000523:psychology; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D008297:Male; D015233:Models, Statistical; D018697:Nootropic Agents / Q000627:therapeutic use; D012044:Regression Analysis; D016903:Drug Monitoring
chemical_list: D018697:Nootropic Agents
keywords: Alzheimer's disease; conditional quantile regression; medication adherence; medication possession ratio; unconditional quantile regression