An epidemiologist is investigating the association between e-cigarette use and acute myocardial infarction (MI). She identifies 250 patients with a recent MI (cases) and 250 patients without MI (controls) and administers a questionnaire assessing past e-cigarette use. Given that this study starts by selecting subjects based on outcome status (MI vs no MI) and then assesses past exposure, which of the following measures of association is most appropriate to quantify the strength of the relationship between e-cigarette use and MI in this study?