What Was the Goal of the Analysis?

Analytic goals for studies can be viewed as either seeking evidence of causality or prediction. We were confused by the goal of the article, “Impact of Gait Speed on the Obesity Paradox in Older Patients With Cardiovascular Disease.”1 We first assumed that the authors were aiming for causality as the title was the “Impact of Gait Speed,” and the stated purpose was “to determine whether gait speed affects the obesity paradox in older patients with cardiovascular disease.” However, given the study design, it is impossible to assess the causal effect of gait speed.