Population-Based Disease Odds for E-Cigarettes and Dual Use versus Cigarettes

Abstract

BACKGROUND: E-cigarettes are promoted as less harmful than cigarettes. There has not been a direct comparison of health effects of e-cigarettes or dual use (concurrently using e-cigarettes and cigarettes) with those of cigarettes in the general population. METHODS: Studies in PubMed, EMBASE, Web of Science, and PsychINFO published through October 1, 2023, were pooled in a random-effects meta-analysis if five or more studies were identified with a disease outcome. We assessed risk of bias with Risk Of Bias In Non-randomized Studies of Exposure and certainty with Grading of Recommendations, Assessment, Development, and Evaluations. Outcomes with fewer studies were summarized but not pooled. RESULTS: We identified 124 odds ratios (94 cross-sectional and 30 longitudinal) from 107 studies. Pooled odds ratios for current e-cigarette versus cigarette use were not different for cardiovascular disease (odds ratio, 0.81; 95% confidence interval, 0.58 to 1.14), stroke (0.73; 0.47 to 1.13), or metabolic dysfunction (0.99; 0.91 to 1.09) but were lower for asthma (0.84; 0.74 to 0.95), chronic obstructive pulmonary disease (0.53; 0.38 to 0.74), and oral disease (0.87; 0.76 to 1.00). Pooled odds ratios for dual use versus cigarettes were increased for all outcomes (range, 1.20 to 1.41). Pooled odds ratios for e-cigarettes and dual use compared with nonuse of either product were increased (e-cigarette range, 1.24 to 1.47; dual use, 1.49 to 3.29). All included studies were assessed as having a low risk of bias. Results were generally not sensitive to study characteristics. Limited studies of other outcomes suggest that e-cigarette use is associated with additional diseases. CONCLUSIONS: There is a need to reassess the assumption that e-cigarette use provides substantial harm reduction across all cigarette-caused diseases, particularly accounting for dual use.

Figure 1.

Comparative Disease Odds Ratios for E-Cigarette Use and Cigarette Smoking. E-cigarette use and cigarette smoking have similar odds of disease for cardiovascular disease, stroke, and metabolic dysfunction and lower odds for asthma (odds ratio, 0.84), COPD (odds ratio, 0.53), and oral disease (odds ratio, 0.87). Confidence intervals include Bonferroni adjustments. Diamonds show point estimates and 95% confidence intervals for pooled odds ratios from random effects meta-analysis. Results for “other” studies were not pooled. CHD denotes coronary heart disease; CI, confidence interval; COPD, chronic obstructive pulmonary disease; COVID, coronavirus disease 2019; CVD, cardiovascular disease; ED, emergency department; HPV, human papillomavirus; MI, myocardial infarction; and OR, odds ratio.

Figure 1.

Comparative Disease Odds Ratios for E-Cigarette Use and Cigarette Smoking. E-cigarette use and cigarette smoking have similar odds of disease for cardiovascular disease, stroke, and metabolic dysfunction and lower odds for asthma (odds ratio, 0.84), COPD (odds ratio, 0.53), and oral disease (odds ratio, 0.87). Confidence intervals include Bonferroni adjustments. Diamonds show point estimates and 95% confidence intervals for pooled odds ratios from random effects meta-analysis. Results for “other” studies were not pooled. CHD denotes coronary heart disease; CI, confidence interval; COPD, chronic obstructive pulmonary disease; COVID, coronavirus disease 2019; CVD, cardiovascular disease; ED, emergency department; HPV, human papillomavirus; MI, myocardial infarction; and OR, odds ratio.

Figure 2.

Comparative Disease Odds Ratios for Cigarette Smoking and Dual Use. Point estimates for odds ratios of disease of all outcomes are above 1 in dual users compared to cigarette smokers (odds ratio, 1.12 to 1.41). Confidence intervals include Bonferroni adjustments. Diamonds show point estimates and 95% confidence intervals for pooled odds ratios from random effects meta-analysis. Results for “other” studies were not pooled. CHD denotes coronary heart disease; CI, confidence interval; COPD, chronic obstructive pulmonary disease; COVID, coronavirus disease 2019; CVD, cardiovascular disease; ED, emergency department; HPV, human papillomavirus; MI, myocardial infarction; and OR, odds ratio.

Figure 2.

Comparative Disease Odds Ratios for Cigarette Smoking and Dual Use. Point estimates for odds ratios of disease of all outcomes are above 1 in dual users compared to cigarette smokers (odds ratio, 1.12 to 1.41). Confidence intervals include Bonferroni adjustments. Diamonds show point estimates and 95% confidence intervals for pooled odds ratios from random effects meta-analysis. Results for “other” studies were not pooled. CHD denotes coronary heart disease; CI, confidence interval; COPD, chronic obstructive pulmonary disease; COVID, coronavirus disease 2019; CVD, cardiovascular disease; ED, emergency department; HPV, human papillomavirus; MI, myocardial infarction; and OR, odds ratio.