Association of mixed use of electronic and conventional cigarettes and exposure to secondhand smoke with prediabetes

Context Despite previous studies regarding the association between smoking and diabetes, the effects of electronic cigarettes and second-hand smoke (SHS) on glucose metabolism and insulin sensitivity have not been fully elucidated. Objective To examine the association of mixed electronic and conventional cigarette use and exposure to SHS with prediabetes. Design Data from the 2014-2018 Korean National Health and Nutrition Examination Survey were analyzed. Setting Nationwide population-based. Participants Of 39,199 participants, 22,385 participants (9,490 men, 12,895 women) without diabetes were included. The main independent variables were smoking behaviors, including exposure to SHS. Interventions None. Main outcome measure(s) Prediabetes (HbA1C of 5.7-6.4%). Results Of 22,385 participants without diabetes, 6,735 had prediabetes. Mixed cigarette use was associated with a 1.57-fold increase in the odds of prediabetes when compared with never-smoking (odds ratio [OR]=1.57, 95% confidence interval [CI]=1.29-1.92) and a 1.27-fold increase when compared with conventional cigarette use only (OR=1.27, 95% CI=1.07-1.52). Participants who were current non-smokers but mixed users in the past had an increased risk of prediabetes (OR=1.54, 95% CI=1.04-2.13). There was no significant association between prediabetes and current non-smoking in individuals with previous conventional cigarette use only. Among never-smokers, exposure to SHS significantly increased the risk of prediabetes (OR=1.16, 95% CI=1.04-1.30). Conclusions Mixed use of electronic and conventional cigarettes and exposure to SHS increased the risk of prediabetes. Further studies are required to comprehensively investigate the molecular biology underlying the effects of previous and current mixed use of electronic cigarettes and SHS on glucose metabolism.