A San Diego study adds new data to the debate over whether e-cigarettes are a helpful or harmful tool in the public health fight against smoking.
In a paper published Wednesday in the British Medical Journal, researchers at UC San Diego report finding a significant spike in the number of Americans quitting smoking in recent years.
"We saw a big increase in 2014-2015," said Shu-Hong Zhu, one of the study's authors and the director of the Center for Research and Intervention in Tobacco Control at UC San Diego.
Zhu and his colleagues wanted to know why more smokers were kicking the habit. He said when they drilled into the population-level data collected by the U.S. Census, they found evidence suggesting that the rise of e-cigarettes may be helping more smokers quit.
"Those people who chose to use e-cigarettes were more likely to try to quit smoking, and in the end, more likely to have successfully quit smoking," Zhu said.
Zhu said the finding comes after a long period when national quitting rates were stubbornly stable. In previous years, only about 4.5 percent of smokers quit cigarettes each year.
But in the years 2014 and 2015 — years when Zhu and his colleagues saw e-cigarettes become increasingly popular — that rate went up to 5.6 percent. It may seem like a small change, but Zhu said at the population level this is a significant bump, representing about 350,000 more smokers quitting.
"This is the first increase we've observed in 15 years," he said.
UC San Francisco smoking expert Stanton Glantz told KPBS in an email that the study was "nicely done," and that it does show a positive effect.
But he said, "Overall, the literature as a whole still shows e-cigarettes associated with less, not more quitting." He also pointed to studies showing that young people who take up e-cigarettes are at greater risk for starting to smoke.
Zhu does not see e-cigarettes as a public health cure-all, and said he would not advise non-smokers to use them. He said he and his colleagues are also not arguing that e-cigarettes are safe, or that getting smokers to quit is as easy as handing them an e-cigarette.
"E-cigarettes are really just one part of the toolbox that could help you quit," he said. "But it's not a cure, by any means. Smokers still have to make a lot of effort in trying to quit."
Nor is Zhu saying that e-cigarettes are the only thing getting more adult smokers to quit. The researchers pointed to a national anti-smoking media campaign that could also be convincing more Americans to stop using tobacco.
But Zhu said the national increase in quitting needs to be explained somehow, and his reading of the data shows compelling associations between smokers who have successfully quit in recent years, and smokers who picked up e-cigarettes in the same period.
He and his colleagues write in their paper, "These findings need to be weighed carefully in regulatory policy making regarding e-cigarettes and in planning tobacco control interventions."