The recent rise in e-cigarette use among US adult smokers is associated with a significant increase in smoking cessation, finds a study published in The BMJ.
This study, based on the largest representative sample of e-cigarette users to date, provides a strong case that e-cigarettes have helped to increase smoking cessation at the population level.
Currently, the scientific community is divided over whether e-cigarettes are an aid to quitting smoking. Some suggest that e-cigarettes will have a positive impact on smoking rates by acting as a nicotine replacement therapy, while others argue that they could reduce the urgency to quit smoking.
So a team of researchers, led by Professor Shu-Hong Zhu at the University of California, set out to examine whether the increase in use of e-cigarettes in the USA, was associated with a change in overall smoking cessation rate at the population level.
They base their findings on five population surveys dating from 2001 to 2015. E-cigarette users were identified from the most recent survey (2014-15) and smoking cessation rates were obtained from those who reported smoking cigarettes 12 months before the survey. Rates from this survey were then compared to four earlier surveys.
Of 161,054 respondents to the 2014-15 survey, 22,548 were current smokers and 2,136 recent quitters. Among them, 38.2% of current smokers and 49.3% of recent quitters had tried e-cigarettes.
The results show that e-cigarette users were more likely than non-users to make a quit attempt (65% v 40%) and more likely to succeed in quitting for at least 3 months (8.2% v 4.8%).
The overall population quit rate for 2014-15 was significantly higher (from 4.5% to 5.6%) than that for 2010-11, and higher than those for all other survey years.
Although the 1.1 percentage point increase in cessation rate might appear small, the researchers point out that it represents approximately 350,000 additional US smokers who quit in 2014-15.
This study has certain limitations, which is common for population surveys. For example, survey questions were limited, which prevented detailed analysis of the quitting process and lack of information on the type of e-cigarette product used. The main strength is use of the largest representative sample of e-cigarette users among the US population.
Nevertheless, the study has two key findings. First, in 2014-15, e-cigarette users attempted to quit cigarette smoking and succeeded in quitting smoking at higher rates than non-users. Second, the overall smoking cessation rate in 2014-15 increased significantly from that of 2010-11.
"Other interventions that occurred concurrently, such as a national campaign showing evocative ads that highlight the serious health consequences of tobacco use, most likely played a role in increasing the cessation rate," say the researchers.
"But this analysis presents a strong case that e-cigarette use also played an important role. These findings need to be weighed carefully in regulatory policy making and in the planning of tobacco control interventions," they add.
In an accompanying editorial, Christopher Bullen, Professor of Public Health at the University of Auckland, says this study raises important points.
He questions whether other tobacco control interventions operating at the same time may have been key triggers to the observed step change, but says Zhu and colleagues "mount a convincing case for why the two most likely candidates - a large federal tobacco tax increase in 2009 and a nationwide mass media campaign - could not be stand-alone reasons for the change in cessation rates."
Bullen also points out that the data came from populations in countries with liberal regulatory approaches towards e-cigarettes, enabling substantial numbers of smokers to make the transition away from smoking.
"In light of this evidence, policymakers in countries contemplating a more restrictive approach to the regulation of e-cigarettes should pause to consider if pursuing such a course of action is the right thing to do for population health," he concludes.