A new study from the Massachusetts General Hospital’s (MGH) Tobacco Research and Treatment Center provides critical population-level evidence demonstrating that using e-cigarettes daily helps U.S. smokers quit smoking combustible (i.e. regular) cigarettes.

The report, published in Nicotine and Tobacco Research online, provides the first longitudinal data about the effectiveness of e-cigarettes for cessation from a survey that reflects the U.S. population. The MGH team analyzed data from the first three years of the Population Assessment of Tobacco and Health (PATH) study, a survey representative of the U.S. adult population that interviews the same individuals each year. The survey allowed the researchers to measure an individual’s change in tobacco use over time.

Using data from more than 8,000 adult smokers, the investigators measured how likely a smoker was to quit smoking and stay quit, comparing daily and non-daily e-cigarette users with those who smoked only regular cigarettes. They found that smokers who used e-cigarettes every day, compared with e-cigarette nonusers, were more likely to quit combustible cigarettes within one year and to stay quit for at least another year. They also found that smokers who used e-cigarettes were no more likely to relapse back to smoking regular cigarettes than smokers not using e-cigarettes.

At the start of the study 3.6 percent of smokers were current daily e-cigarette users; 18 percent were current non-daily e-cigarette users; and 78 percent did not use e-cigarettes at all

“This study suggests e-cigarettes may be helpful for some smokers who are not able to quit with existing treatments.” — Nancy Rigotti

By the second and third years of data gathering, daily e-cigarette users reported a higher rate of prolonged abstinence from cigarette smoking (11 percent) than nonusers (6 percent). Smokers who used e-cigarettes, but not daily, were not more likely than nonusers to demonstrate prolonged abstinence from combustible cigarettes.

“This finding suggests that smokers who use e-cigarettes to quit smoking need to use them regularly — every day — for these products to be most helpful,” said lead author Sara Kalkhoran, an MGH physician and assistant professor of medicine at Harvard Medical School (HMS).

“Smokers who plan to stop smoking should still be encouraged to first use FDA-approved therapies rather than e-cigarettes,” said Nancy Rigotti, senior author of the paper and director of the MGH Tobacco Research and Treatment Center. FDA-approved therapies for smoking cessation include varenicline, bupropion, or nicotine patches, gum, or lozenges. “But this study suggests e-cigarettes may be helpful for some smokers who are not able to quit with these existing treatments,” she added.

E-cigarettes contain nicotine but do not burn tobacco, which is responsible for many of the health problems associated with smoking combustible cigarettes. “For a smoker, e-cigarettes are less harmful to their health than continuing to smoke cigarettes,” said Rigotti, who is also a professor of medicine at HMS. “But e-cigarettes have become popular so quickly that many questions remain about how they can best be used to help smokers to quit and minimize any harm.” The third member of this MGH research team was Yuchiao Chang.

Although the rate of smoking in this country has been falling, the U.S. Centers for Disease Control reports that more than 34 million Americans currently smoke cigarettes. Smoking causes more than 480,000 deaths per year in this country alone, including more than 41,000 deaths from secondhand smoke exposure.