Neglecting regression to the mean continues to lead to unwarranted conclusions: Letter regarding "The magnitude of weight loss induced by metformin is independently associated with BMI at baseline in newly diagnosed type 2 diabetes: Post-hoc analysis from data of a phase IV open-labeled trial"

Abstract

As the prevalence of type 2 diabetes mellitus and obesity increases worldwide, scientifically rigorous research is needed in this field to determine effective interventions for the prevention and treatment of these chronic diseases. In a recent study published in this journal, Zhou et al. conclude that metformin, a drug used for treatment of type 2 diabetes mellitus, can be used effectively for weight loss, and that this effect is even more pronounced in individuals who weigh more at baseline. Unfortunately, we believe these results to be due to the regression to the mean (RTM) phenomenon, which weakens the causal inference proposed in this study. The conclusions of Zhou et al. that metformin is an effective strategy for weight loss in individuals with type 2 diabetes mellitus are not substantiated due to the lack of a control group and failure to consider other factors that may have confounded these results.

Keywords: body weight loss; metformin; statistics.