January 24, 2018 | Erin Bluvas, bluvase@sc.edu 

The National Academies of Sciences, Engineering, and Medicine, with support from the Food and Drug Administration's Center for Tobacco Products, convened a committee of experts to conduct a review of the scientific evidence about e-cigarettes and health. Epidemiology and biostatistics professor and chair Anthony Alberg, a nationally recognized cancer researcher with expertise in tobacco control, was among the specialists invited to join the committee that produced the resulting report: Public Health Consequences of E-Cigarettes.

Millions of Americans use e-cigarettes, and young people use them more than any other tobacco product. Though widely popular, particularly among young people age 17 and under, there is little known about the health effects of e-cigarettes, and perceptions of their potential risks and benefits vary significantly among the public, users, researchers, and healthcare providers.

Public Health Consequences of E-Cigarettes represents the first coordinated effort to provide a comprehensive review of the existing evidence related to e-cigarettes as well as recommendations for future research by improving study designs and focusing on priority areas that have not been examined sufficiently—if at all. 

Conclusions

In the report, the committee offers 47 conclusions related to the composition of e-cigarettes (i.e., key constituents), effects on human health, initiation and cessation of combustible tobacco cigarette use, and harm reduction. Depending on the availability of evidence and the strength of the connection between e-cigarettes and various factors, the report characterizes each conclusion based on its evidence level (e.g., conclusive, substantial, moderate, limited, insufficient, no available evidence).

For example, among the conclusions related to the constituents (i.e., the makeup) of e-cigarettes, the authors state that there is substantial evidence that nicotine intake from e-cigarette devices among experienced adult e-cigarette users can be comparable to that from combustible tobacco cigarettes. They also found there is conclusive evidence that in addition to nicotine, most e-cigarette products contain and emit numerous potentially toxic substances.

In terms of health effects, the report concluded that there are heart rate (substantial evidence) and blood pressure (moderate evidence) increases after intake from e-cigarettes. However, there is insufficient evidence that e-cigarette use is associated with long-term changes in heart rate, blood pressure, and cardiac geometry and function. Further, there is no available evidence for whether or not e-cigarettes are associated with long-term risks of chronic diseases such as cancer and cardiovascular disease.

With regard to initiation and cessation of combustible cigarettes, the committee found substantial evidence that e-cigarette use increases the risk of ever using combustible tobacco cigarettes among youth and young adults, and they found moderate evidence that e-cigarette users who went on to smoke  combustible tobacco cigarettes have an increased frequency and intensity of subsequent combustible tobacco cigarette smoking. Further, there is insufficient evidence as to the effectiveness of e-cigarettes as cessation aids.

Conclusions related to harm reduction include conclusive evidence that switching from combustible cigarettes to e-cigarettes reduces users’ exposure to numerous toxicants and carcinogens present in combustible cigarettes. Similarly, there is moderate evidence that second-hand exposure to nicotine and particulates is lower from e-cigarettes compared with combustible tobacco cigarettes.

A complete list of the authors’ conclusions can be found in the report  or in supporting documents organized by outcomes  or level of evidence.

Recommendations

The report also contains in-depth recommendations for both addressing gaps in what is known about e-cigarettes and improving research methods and quality.

“This report provides a useful summary of the current state of the evidence with respect to the public health implications of e-cigarette use and a useful framework for where future research investments are needed,” says Alberg. “Much of the controversy so far about e-cigarettes is the frame of reference: whether one is addressing the absolute risk of e-cigarettes—compared to no exposure—or rather comparing e-cigarettes with relative to the risks of combustible tobacco cigarettes; we need both forms of evidence to guide prudent public health policy.”

Future research should study the impact of e-cigarette use on indoor air quality as well as the risks of secondhand e-cigarette exposure on populations such as vape shop employees, children, pregnant women, and patients with cardiorespiratory disease who live with adults who use e-cigarettes. Another suggestion involves examining periodontal disease in e-cigarette users who have not used combustible cigarettes.

Long-term clinical and epidemiological studies, comparing cardiovascular, respiratory, and other health outcomes among e-cigarette versus combustible cigarettes users, are needed as well. Longitudinal cohort studies are needed to better understand the trajectory of dependence over time in youth and young adults. The authors also note the importance of developing effective communication strategies about the risk of e-cigarettes compared to combustible cigarettes.

To improve research methods and quality, the report recommends approaches such as developing and validating methods to produce aerosols and analyze target components of e-cigarettes, standardizing measures for puffing conditions, and streamlining methods to measure particle size distribution and respiratory deposition of e-cigarette aerosols. At the population level, studies should build on nationally representative surveys of adults to monitor patterns of e-cigarette use.

A full list of recommendations can be found here  and is included in the report.

Overall conclusions from the report note that e-cigarettes, though not without risk, contain fewer toxicants, show significantly less biological activity, and might be useful as an aid in cessation for smokers who use e-cigarettes exclusively. E-cigarettes deliver nicotine in a similar manner, and young people who begin smoking with e-cigarettes are more likely to transition to combustible cigarettes.

“Perhaps the key finding of the report is the substantial evidence implicating e-cigarettes as a risk factor for subsequent combustible tobacco smoking in youth—this has profound negative implications for public health,” says Alberg. “Randomized trials to test whether e-cigarettes are an efficacious cessation aid for smokers trying to quit are a priority.”

The net public health outcome from e-cigarettes will depend on the positive and negative consequences, which will require more and better research. This additional research will help determine whether e-cigarettes reduce or induce harm at both the individual and population levels.

The National Academies of Science, Engineering, and Medicine has also provided a summary of highlights  from the report as well as report release slides and a press release.