Cardiovascular effects of e-cigarettes
Electronic cigarettes and health with special focus on cardiovascular effects: position paper of the European Association of Preventive Cardiology (EAPC)
E-cigarettes are marketed as a safe alternative for traditional cigarettes and are suggested as a method to reduce or quit tobacco smoking. However, there is an increasing body of evidence that e-cigarettes are not harmless [1-5]. This position paper of the European Association of Preventive Cardiology (EAPC) provides an overview of the prevalence of e-cigarette use, CV effects of e-cigarette smoking and discusses the lack of evidence on the effects of e-cigarettes on smoking cessation and differences in regulatory measures in different countries. Moreover, the EAPC gives recommendations concerning e-cigarette usage.
Prevalence of e-cigarette use and effects of use in young individuals
The prevalence of e-cigarette use is difficult to define as the definition of e-cigarette usage varies. Furthermore, the prevalence is heterogenous across countries and sometimes within a country, and prevalence of e-cigarette has changed over time, with a rise in prevalence in more recent versus older surveys . Prevalence of ever use ranged from 0 to 56.6%, prevalence of past 30-day use ranged from 2.0% to 35.0%, and prevalence of daily use ranged from 0.2% to 1.7%.
Consistently higher prevalence rates were reported in studies targeting youth or students. Studies reported an increase from 5% to 25% between 2013 and 2019 in prevalence of e-cigarette use in young individuals [7-9]. E-cigarette use and secondary exposure have been related to increased asthma attacks in young people and there is evidence that nicotine from e-cigarettes might affect brain maturation [10,11]. Furthermore, nicotine has been shown to have adverse effects in pregnancy and there is no evidence providing e-cigarettes to be safe during pregnancy [12-14]. Together, this makes e-cigarettes a new potential health hazard for children and adolescents. Furthermore, there is increasing evidence that young people who have never smoked and use e-cigarettes might double their chance of starting to smoke cigarettes later in life [15-18]. Increased awareness and education are therefore needed to inform young individuals of the potential adverse health effects of e-cigarettes in order to prevent and decrease use of e-cigarettes.
CV effects of e-cigarette use
It is believed that e-cigarettes are less harmful than tobacco cigarettes [19, 20], however e-cigarettes do contain potential toxicants and exert a variety of biological effects . Direct evidence on clinical CV effects of e-cigarettes from clinical trials or long-term cohort studies is currently not available. Consequences of long-term use are therefore largely unknown. The only epidemiological evidence that is currently available is based on observational data from the National Health Interviews Surveys of 2014 (n=36697) and 2016 (n=33028). These data suggest an increased risk of MI in e-cigarette users (OR 1.79, 95%CI 1.20-2.66), although to a lesser extent than in those who smoked conventional cigarettes (OR 2.72, 95%CI 2.29-3.24) . Our current knowledge on how e-cigarettes affect the CV system is mainly based on non-randomised observational studies of small sample sizes and short-term follow-up. CV effects of e-cigarettes have been assessed indirectly, based on mechanistic studies. For example, a meta-analysis showed that exposure to e-cigarettes acutely increased heart rate (HR), SBP and DBP. Switching from tobacco smoking to chronic e-cigarette smoking did not affect HR, but significantly reduced SBP and DBP . An observational study showed that smoking e-cigarettes for >30 min had an adverse effect on arterial stiffness that was similar to that of traditional cigarettes . However, another study did not show an effect of e-cigarette use on arterial stiffness . Smoking of e-cigarettes has been associated with a rapid increase of endothelial progenitor cells, which could be linked to acute endothelial dysfunction and/or vascular injury . A case-control study showed that e-cigarette use for at least one year was associated with increased levels of oxidative stress and a shift in cardiac autonomic balance toward sympathetic predominance . In addition, another study showed that acute exposure to nicotine-containing e-cigarettes, as compared to exposure to a sham-control or non-nicotine e-cigarettes, was associated with increased cardiac sympathetic nerve activity, which could be associated with increased cardiac risk . Besides nicotine, other aerosol constituents in e-cigarettes that may exert adverse CV effects include oxidizing chemicals and particulate matter (PM) . In addition, a systematic review of 38 studies that investigated CV effects of e-cigarettes concluded that most studies suggest potential CV harm through mechanisms that increase the risk of thrombosis and atherosclerosis . However, it remains uncertain whether the hemodynamic changes lead to a clinical risk of CVD and these findings should be interpreted with caution. Overall, while long-term effects of e-cigarette use remain unknown at this point, the existing evidence suggests that e-cigarettes should not be regarded as a safe product in terms of CV effects.
The complete list of recommendations from the EAPC population science and public health section has been published in the position paper. In short, the provided recommendations include that health professionals should inform patients and the general public of possible (CV) risks of e-cigarette use. Furthermore, there is currently a lack of robust longitudinal data on the impact of e-cigarettes on smoking cessation. Using e-cigarettes in an attempt to stop smoking should only be considered alongside a formal tobacco cessation program. Countries lacking a legal framework for e-cigarettes should create one. Moreover, e-cigarette legislation should be regularly be updated because of the rapidly evolving market. A strict regulation of e-cigarette marketing and advertising is necessary, and the general public should be made aware of the potential adverse effects. Abstinence of e-cigarettes during pregnancy should for instance be recommended. Prospective studies assessing multiple subclinical and clinical effects of e-cigarette smoking on multiple systems (including the CV system) are highly needed and government and non-government funding should be encouraged to support such research. To allow direct comparison between future studies, researchers should apply standardized methodologies. Finally, countries are encouraged to follow the Framework Convention of Tobacco Control of the WHO.