Sports Events and Acute Coronary Syndrome: Possible Confounding Factors and Bias

Abstract

Dear Editor, The relationship between sports events and ACS (Acute Coronary Syndrome) has been the subject of some studies in the literature, with controversial results, and was recently addressed by Borges et al1 in the manuscript entitled Soccer Cup as a Trigger of Cardiovascular Events, published in volume 6 of 2013 of ABC. The authors observed a higher incidence of AMI (Acute Myocardial Infarction) in match days of the FIFA World Cup and, in particular, on Brazilian games, concluding that this sporting event can act as a trigger of AMI in Brazilians. However, considerations of possible confounding factors and bias should be made to present to readers a better interpretation of the data presented. Firstly, the literature describes that, during sporting events, viewers tend to have numerous risk behaviors for cardiovascular disease, such as the intake of large amounts of alcohol, consumption of fatty food, and use illicit drugs and smoking2,3. These factors have also been described as possible triggers for ACS4,5, making the association between FIFA World Cup and ACS established in the research of Borges et al1 subject to a number of confounding factors and hindering the interpretation of results. Defining, as the authors intend, if the World Cup could be seen as a direct trigger for ACS is not possible or merely if it entails a number of risk conditions already well described in the literature. Furthermore, the use of research findings by observing groups of people to infer causal relationships in individuals may result in ecological fallacy5, since it is not possible to state that all individuals who attended the event were exposed the same way. Therefore, the study design presented by Borges et al1 does not allow the establishment of a direct association between the occurrence of ACS and the FIFA World Cup, and the interpretation of the study results should be performed carefully, taking into account the potential confounding factors and bias of ecological study.