Results from a large national prospective cohort study of adults demonstrated that the use of electronic cigarettes is associated with an increased risk of asthma, chronic obstructive pulmonary disease (COPD), emphysema, and chronic bronchitis – independent of cigarette smoking and other combustible tobacco product use.
“Our longitudinal results are consistent with the findings of prior population studies,” researchers led by Wubin Xie, DrPH, MPH, wrote in a study published online in JAMA Network Open. “With a more refined study design assessing multiple respiratory conditions and extensive sensitivity checks to mitigate bias from reverse causation and residual confounding by cigarette smoking and other tobacco product use, our results strengthen the evidence of the potential role of e-cigarette use in pulmonary disease pathogenesis. The findings may be used to inform counseling of patients on the potential risks of e-cigarette use.”
Dr. Xie of Boston University, and colleagues used data from the Population Assessment of Tobacco and Health (PATH) study waves 1-4 to examine the association of e-cigarette use with incident respiratory conditions, including COPD, emphysema, chronic bronchitis, and asthma. An earlier analysis of PATH data found an association between e-cigarette use with a composite respiratory disease outcome, but it did not consider the timing of respiratory events over follow-up and was underpowered to evaluate specific respiratory conditions.
The current analysis included data from 21,618 U.S. adults who were surveyed in four waves of PATH between 2013 and 2018. Of these, 49% were men, 65% were non-Hispanic White, 12% were non-Hispanic Black, 16% were Hispanic, and the remainder were non-Hispanic other. Their mean pack-years was 6.7 at baseline, 26% had self-reported hypertension, and their mean body mass index was 27.8 kg/m2. The analysis was limited to data from the wave 1 cohort of adults and the prospective follow-up at waves 2-4 from public use files. It excluded adults who reported a history of a respiratory condition such as COPD, emphysema, chronic bronchitis, or asthma at wave 1 (baseline).
Two-thirds of respondents (66%) were never e-cigarette users, 12% were former e-cigarette users, and 5% were current e-cigarette users. After the researchers adjusted for cigarette and other combustible tobacco product use, demographic characteristics, and chronic health conditions, they observed an increased risk of respiratory disease among former e-cigarette users (incidence rate ratio, 1.28) and current e-cigarette users (IRR, 1.31). Among respondents with good self-reported health, the IRR for former e-cigarette users was 1.21 and the IRR for current e-cigarette users was 1.43. As for specific respiratory diseases among current e-cigarette users, the IRR was 1.33 for chronic bronchitis, 1.69 for emphysema, 1.57 for COPD, and 1.31 for asthma.
“Our findings on clinical outcome were consistent with studies assessing in vivo biomarkers of e-cigarette exposure in animal subjects, human participants, and population studies,” the authors wrote. “Studies have documented that exclusive e-cigarette use may be associated with higher exposure to harmful and potentially harmful constituents, compared with tobacco nonuse. The potential mechanisms of the association of e-cigarette exposure with pulmonary diseases include pulmonary inflammation, increased oxidative stress, and inhibited immune response. Animal studies have generated substantial evidence on e-cigarette exposure and emphysematous lung destruction, loss of pulmonary capillaries, reduced small airway function, and airway hyperresponsiveness, suggesting the plausibility of e-cigarettes causing chronic lung diseases.”
They acknowledged certain limitations of the study, including its reliance on self-reported measures of e-cigarette and other tobacco product use and its reliance on self-reported diagnoses of respiratory diseases.
The study was supported by grants from the National Heart, Lung, and Blood Institute; the Food and Drug Administration Center for Tobacco Products; and the American Lung Association Public Policy Research Award. Dr. Xie reported having no financial disclosures. His coauthors reported having received research grants and personal fees from a variety of sources.
SOURCE: Xie W et al. JAMA Netw Open. 2020 Nov 12. doi: 10.1001/jamanetworkopen.2020.20816