Perceived harm of e-cigarettes relative to conventional cigarettes: Comparison among different measures in the US and Vietnam

INTRODUCTION: Evidence shows the inconsistencies in perceived harm of e-cigarettes between direct (single question) and indirect (assessing perceived harm separately by a single question and subtracting their score) measures. While the validity of both measures was tested by assessing their association with criterion variables (i.e., ever-trying e-cigarettes), further validation research is needed given existing limitations. METHODS: We analyzed data from Population Assessment of Tobacco and Health Study Wave 6 in the US and a provincial version of the Global Adult Tobacco Survey 2020 in Vietnam. Comparative harm of cigarettes and e-cigarettes was measured using direct and indirect method. A new criterion validity measure - "I use e-cigarettes because they might be less harmful to me than smoking cigarettes" - was introduced. RESULTS: In the general US population, a higher proportion of participants perceived e-cigarettes as less harmful than cigarettes when assessed using the indirect method compared to the direct method (31.56% vs. 13.70%). Additionally, although many US e-cigarette users indicated that they used e-cigarettes because they might be less harmful than cigarettes, among these people only 61.43% reported e-cigarettes to be less harmful when using the direct method but this proportion was higher (67.28%) for the indirect method. In Vietnam, this proportion was higher, at 76.68% using the direct method. CONCLUSION: This study emphasizes the significance of including and reporting multiple measures within a single survey to achieve a comprehensive understanding of perceived harm.