Observational Study
A research study where outcomes are recorded without intervening to assign treatments. Observational studies include cohort studies, case-control studies, and cross-sectional studies. They provide real-world evidence that complements controlled trials but cannot establish definitive cause and effect.
Technical Context
The three main observational designs — cohort, case-control, and cross-sectional — have complementary strengths. Cross-sectional studies examine exposure and outcome at a single time point (useful for prevalence estimation but cannot establish temporal sequence). All observational studies face confounding: in GLP-1 RA observational research, patients prescribed GLP-1 RAs may differ systematically from those on other treatments (confounding by indication). Statistical methods to address confounding include: multivariable regression, propensity score matching (balancing measured confounders), instrumental variable analysis (exploiting natural quasi-randomisation), and difference-in-differences analysis (comparing pre/post trends). Regulatory agencies increasingly use real-world evidence from observational studies to supplement clinical trial data.