They said in the paper: 'This study, based on the largest representative sample of e-cigarette users to date, provides a strong case that e-cigarette use was associated with an increase in smoking cessation at the population level.
In background notes, the researchers said use of electronic cigarettes in the United States became noticeable around 2010 and increased dramatically by 2014 - which would coincide with the rising quit-smoking rates.
"Use of e-cigarettes was associated both with a higher quit rate for individuals as well as at the population level; driving an increase in the overall number of people quitting", said Shu-Hong Zhu, study author and UC San Diego professor of Family Medicine and Public Health and director of the Center for Research and Intervention in Tobacco Control, in a statement.
Mr Hajek said: 'It's absolutely clear that e-cigarettes help smokers replace cigarettes'.
Published this week in the British Medical Journal, the study titled 'E-cigarette use and associated changes in population smoking cessation: evidence from USA current population surveys' examined more than 160,000 respondents of different smoking statuses (never smoked through to heavy smokers), including 2136 recent quitters, from five different population studies.
Smoking rates have been generally declining for decades.
E-cigarette users were more likely to attempt to quit smoking (65.1% vs. 40.1%) and more likely to succeed in quitting (8.2% vs. 4.8%). This supports the thesis that less strict control over e-cigarettes would be positive.
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Here, "cessation rate" was how many people, who were smokers 12 months before the survey, quit for at least three months.
"This is the first statistically significant increase observed in population smoking cessation among U.S. adults in almost a quarter of a century".
"With proper regulation, we could increase the potential of e-cigarettes to reduce the horrific toll of cigarette smoking in our society", he added.
"The available evidence clearly shows that e-cigarettes are significantly safer than traditional tobacco products and that they have helped millions of people around the world cut down and quit smoking".
Other study limitations included not addressing the long-term effects of e-cigs or investigating if the use of e-cigs leads people to start smoking. Traditional cigarette smoke is estimated to raise a smoker's' risk for cancer by less than 1 part in 1,000, therefore, the risk of formaldehyde in the vapor of e-cigs is not as significant.
"If the 40 million smokers in the US switched to e-cigarettes, the nation would be a lot healthier for it", Schroeder said. "But if those don't work - try an e-cigarette".