For years, e-cigarettes have been promoted not only as a less harmful alternative to traditional cigarettes, but also as an option for current smokers to quit or reduce their use of tobacco. New research indicates, however, that e-cigarettes may have the opposite effect, especially in younger individuals who have never smoked.
In a March study published in PLOS ONE,(journals.plos.org) researchers from the Norris Cotton Cancer Center at Dartmouth College concluded that although e-cigarettes may be of some benefit in adults who are trying to quit smoking combustible cigarettes, they may act as a gateway product in other people. In particular, the study findings suggest that e-cigarette use may be associated with teenagers and young adults starting to smoke traditional cigarettes and, eventually, becoming daily smokers.
Study Model and Results
In the study, the authors constructed a population-level risk model using 2014 U.S. census data, previously published study results on e-cigarette use and its association with smoking cessation or initiation, and national health or tobacco use surveys on e-cigarette use. Unlike previous studies, the model considered multiple population subgroups, including current smokers and individuals who had never smoked cigarettes. For current smokers, the authors reviewed information on adults ages 25 to 69; for never-smokers, the authors analyzed data on adolescents and young adults ages 12 to 29.
The model attempted to measure the benefits or harms of e-cigarette use through three estimated outcomes:
- the number of current combustible cigarette smokers who would quit smoking through the use of e-cigarettes and remain abstinent for seven or more years;
- the number of adolescents and young adults who never smoked but began smoking after using e-cigarettes and eventually became long-term daily smokers later in life; and
- the total number of years of life gained or lost by these groups through e-cigarette use.
- Results of a recent study indicate that e-cigarette use by teenagers and young adults may be associated with these individuals taking up smoking traditional cigarettes as they get older.
- Using a population model, the study authors estimated that individuals who transitioned from using e-cigarettes to becoming daily combustible cigarette smokers would lose about 1.5 million years of life.
- The authors suggest that e-cigarette use may confer more harm than good and note that to provide real benefit, the effectiveness of e-cigarettes as a smoking cessation tool would need to be considerably higher than it currently is.
Data drawn from the information sources cited above indicated that in 2014, 3,490,000 current adult cigarette smokers who had attempted to quit smoking in the past year had also currently used e-cigarettes. Additionally, 3,640,000 never-cigarette smoking adolescents and young adults had ever used e-cigarettes. The authors validated the model against one-year intermediate outcomes from 2013 data sources.
Based on the available information, the study model estimated that using e-cigarettes in 2014 would help an additional 2,070 current adult smokers quit in 2015 and remain abstinent from smoking for at least seven years compared with those who did not currently use e-cigarettes. The model also estimated that about 168,000 never-cigarette smoking adolescents and young adults who used e-cigarettes in 2014 would start smoking combustible cigarettes during the following year and would become daily smokers by age 35-39, compared with those who never used e-cigarettes.
Although current adult cigarette smokers may experience a relative benefit from using e-cigarettes to quit smoking compared with current smokers who never used e-cigarettes, the net effect remains in the red. Specifically, the model estimated that the 2,070 additional long-term quitters would gain -3,000 years of life -- still an overall negative loss of life.
Finally, the model estimated that the adolescents and young adults who transitioned from using e-cigarettes to becoming daily cigarette smokers would lose about 1.5 million years of life. This estimate was based on a 95 percent relative harm reduction of e-cigarette use compared with smoking traditional cigarettes, a figure the authors called "optimistic" given the current lack of evidence on the harms of e-cigarettes. Additional analysis showed that the total number of years of life lost increased as the relative harm reduction of e-cigarette use dropped, reaching 1.6 million years when the relative harm reduction was decreased to about 50 percent.
"Based on the most up-to-date published evidence, our model estimated that e-cigarette use in 2014 represents a population-level harm of about 1.6 million years of life lost over the lifetime of all adolescent and young adult never-cigarette smokers and adult current cigarette smokers in the 2014 U.S. population," the authors wrote. "Our model also estimated even greater population-level harm if e-cigarette use confers long-term health risks."
Although the study authors suggested that e-cigarettes could provide some benefits if they were more effective in helping people quit smoking, they cautioned that e-cigarettes also carry their own health risks. Previous research(pubs.acs.org) has shown, for example, that e-cigarettes contain a number of harmful and potentially harmful ingredients, including heavy metals and chemicals such as diacetyl, which has been linked to lung disease.
Study results have also shown that e-cigarette use can negatively affect the immune system(www.ncbi.nlm.nih.gov) and significantly impair respiratory(www.atsjournals.org) and cardiovascular(jaha.ahajournals.org) function.
The authors noted several limitations to their study, including
- uncertainty regarding whether e-cigarette use directly causes cigarette smoking in adolescents and young adults;
- inability to identify the types of e-cigarettes, each of which may deliver different levels of nicotine, used by adults who are current smokers;
- no consideration of the possibility that e-cigarette use in current smokers may cause a decline in the number of traditional cigarettes smoked per day; and
- no consideration of potential harms or benefits resulting from e-cigarette use among former smokers at the population level because of a lack of evidence regarding whether e-cigarette use among former cigarette smokers led to higher or lower rates of relapse.
Despite these limitations, the authors concluded that their study "suggests that e-cigarettes pose more harm than they confer benefit at the population level."
"If e-cigarettes are to confer a net population-level benefit in the future, the effectiveness of e-cigarettes as a smoking cessation tool will need to be much higher than it currently is," the authors stated.
Implications and Related Studies
Jennifer Frost, M.D., medical director for the AAFP's Health of the Public and Science Division, told AAFP News that the study highlights the potential negative health impact of e-cigarettes. She encouraged family physicians to ask patients about their use of e-cigarettes as well as traditional cigarettes.
"Family physicians should remember e-cigarettes when asking their patients whether or not they smoke," Frost said. 'This may mean not only asking, 'Do you smoke?' but also asking, 'Do you vape or use electronic cigarettes?'" Frost added that although many people promote e-cigarettes as less harmful than traditional cigarettes, it's important to recognize that the true harms of these products still are not known.
Several other recently published studies have documented similar associations between e-cigarette use and tobacco smoking.
In January, the National Academies of Sciences, Engineering and Medicine published a comprehensive report(www.nap.edu) on the health effects of e-cigarettes, and found "substantial evidence" to show that e-cigarette use by adolescents and young adults increases the risk of ever using traditional cigarettes.
A March Annals of Internal Medicine study(annals.org) of more than 1,300 recently hospitalized smokers who planned to discontinue smoking found that using e-cigarettes intermittently and concurrently with other tobacco cessation treatments "did not seem to aid quitting and may have hampered" the efforts of some individuals to quit.
Related AAFP News Coverage
FDA Proposes Reducing Nicotine in Combustible Cigarettes
More From AAFP
American Family Physician: Electronic Cigarettes: Cautions and Concerns
CDC: E-Cigarettes and Young People: A Public Health Concern(www.cdc.gov)