The Risks of Misunderstanding the Term "Risk Factor": A Primer with Suggestions to Improve Sports Medicine.

The term "risk factor" is commonly used in research. Although many interpret the term to imply that the risk factor causes the outcome, others use the term to mean a marker for the outcome, which may or may not be a cause of the outcome. How the term risk factor is interpreted can importantly influence the way that study findings are applied in real world settings. For example, if a risk factor is wrongly interpreted to be a cause of an outcome when it is merely associated with the outcome because of noncausal reasons, then wasteful interventions may be developed, recommended, and implemented. The primary aims of this article are (1) to describe how varying definitions of the term risk factor can cause misunderstandings and potentially negatively impact the field of sports medicine, and (2) to propose new, more specific, terminology. We first review some basic concepts on how variables can be associated due to either causal or noncausal reasons and then discuss possible explanations for why the term risk factor continues to be misunderstood. We illustrate how using the term risk factor without further specification creates misunderstandings that can lead to the development and implementation of ineffective interventions. Finally, with the hope of improving communication and avoiding ambiguity in sports medicine, we suggest using "causal risk factor" if the evidence supports causality, "noncausal risk factor" if the evidence does not support causality, and "risk marker" for those not wishing to commit to a causal or noncausal claim.