Ultraprocessed Food and Cardiovascular Risk: Estimating the Number Needed to Harm in an Unfamiliar Situation

The Number Needed to Harm (NNH) statistic is a measure of effect size. It is defined as the number of patients who need to be treated for one additional patient to experience an adverse outcome. The NNH is conventionally calculated in the context of a randomized controlled trial. This article explains how the NNH can be estimated and understood for a lifestyle behavior in the context of an observational study in which the outcome was described using an uncommon unit. The lifestyle behavior, here, was the intake of ultraprocessed food and the outcome was stated as the number of events per 1000 person-years. The NNH can be estimated from the data provided, expressed in different ways, and converted into a form that is relevant to clinical practice.