title: Pitfalls in assessing the effect of time-varying covariates in cross-sectional studies.
authors.forename: H
authors.initials: H
authors.lastname: Brenner
mesh_terms: D001250:Asthma, Exercise-Induced / Q000453:epidemiology; D002648:Child; D003430:Cross-Sectional Studies; D003627:Data Interpretation, Statistical; D006801:Humans; D013995:Time