E-cigarettes seeing US smokers quit: study

Scientists from California say their findings provide a "strong case" that e-cigarettes have helped to increase rates of people quitting smoking.

American researchers say electronic cigarettes are linked to people quitting smoking. (AAP)

A rise in the use of electronic cigarettes among American adults is linked to a significant increase in the numbers of people quitting smoking, researchers say.

In a study published in the BMJ British medical journal, scientists from California said their findings were based on the largest representative sample of e-cigarette users to date and provided a "strong case" that e-cigarettes have helped to increase rates of smoking cessation.

"These findings need to be weighed carefully in regulatory policy making and in the planning of tobacco control interventions," the researchers, led by Shu-Hong Zhu at the University of California, said in their study.

The global scientific community is divided over e-cigarettes and whether they are a useful public health tool as a nicotine replacement therapy or a potential "gateway" for young people to move on to start smoking tobacco.

Many specialists, including health experts at Public Health England, think e-cigarettes, which contain nicotine but no tobacco, are a lower-risk alternative to smoking.

But the US surgeon general last year urged lawmakers to impose price and tax policies that would discourage their use.

Zhu's study used five US population surveys dating from 2001 to 2015. E-cigarette users were identified from the most recent survey in 2014/15, and smoking quit rates were obtained from those who had reported smoking cigarettes 12 months before the survey. Rates were then compared to four earlier surveys.

The results showed that e-cigarette users were more likely than non-users to make a quit attempt (65 per cent versus 40 per cent) and more likely to succeed in quitting smoking tobacco for at least three months.

The overall population quit rate for 2014/15 was 5.6 per cent, up from 4.5 per cent in 2010/11, and higher than the rates in all other survey years.

The researchers said that while the 1.1 percentage point rise in the smoking cessation seemed small, it represented around 350,000 additional US smokers who quit in 2014/15.