Association of Mixed Use of Electronic and Conventional Cigarettes and Exposure to Secondhand Smoke With Prediabetes: Results From National Cross-Sectional Surveys

Background: Evaluating whether the cigarette type used in the past and present and exposure to secondhand smoke are associated with prediabetes is important for future research and public health interventions. This study aimed to examine the association of mixed electronic and conventional cigarette use and exposure to secondhand smoke with prediabetes. Methods: Data from the 2014-2018 Korean National Health and Nutrition Examination Survey were analyzed. Prediabetes was defined as an HbA1C of 5·7–6·4%. Participants were categorized according to type of cigarette used and secondhand smoke exposure. Multiple logistic regression analysis was performed. Findings: Of the 22,385 participants without diabetes, 6,735 had prediabetes. Mixed cigarette use was associated with prediabetes when compared with only conventional cigarette use (odds ratio [OR]=1·27, 95% confidence interval [CI]=1·09–1·49). Participants who were current non-smokers but mixed users in the past had an increased risk of prediabetes (OR=1·54, 95% CI=1·06–2·23). However, there was no significant association between current non-smoking but only conventional cigarette use in the past and prediabetes. Among never-smokers, exposure to secondhand smoke significantly increased the risk of prediabetes (OR=1·15, 95% CI=1·03–1·28). Interpretation: Mixed use of electronic and conventional cigarettes and exposure to secondhand smoke was associated with prediabetes. Furthermore, the mixed use in the past was associated with prediabetes even if the cigarette was not used currently. In future research on the determining the effect of smoking on prediabetes and interventions to prevent diabetes, the cigarette type used should be considered. Funding Information: None. Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: This study used data obtained from the 2014 and 2018 Korean National Health and Nutrition Examination Survey (KNHANES). The KNHANES is a nationwide population-based survey designed to acquire information regarding the health and nutrition of people in South Korea. The survey is performed by the Korean Centers for Disease Control and Prevention (KCDC) and combines a health interview with a physical examination and nutrition survey. The KNHANES protocols were approved by the Institutional Review Board of the KCDC (IRB No. 2018-01-03-P-A), and the research complied with the tenets of the Declaration of Helsinki for medical research involving human subjects. Informed consent was obtained from all participants.