Limitations
There are some limitations to our study which we need to emphasize. First, the cross-sectional nature of our data implies that the characterization of the syncopal event, personal and familiar history may be subject to recall bias, and this may be particularly true for children participating in the survey. Yet, we had a cohort of the general population of large dimensions, to which we applied a digital-based questionnaire mainly composed of closed questions and few open fields, thus enhancing our ability for complete data collection. Second, our questionnaire did not allow to establish a temporal relationship between syncope and fever or the type or quantity of physical exercise since the inclusion of such questions would have increased the complexity of the questionnaire. Third, we studied a young adult cohort with children and young-adults (<40 years-old), which included both athletes and non-athletes, therefore our findings should only be applied to individuals belonging to these age strata. Finally, despite the clinical suspicion that individuals with US may be at an increased risk for adverse cardiovascular events, we cannot make the definite diagnosis of cardiac syncope or directly infer the risk of SCD based on our data, given the cross-sectional nature of our study. We will be contacting some of the high risk-respondent participants in the near future to perform further and more detailed cardiovascular work-up, as well as a long-term follow-up.