Some experts have suggested that e-cigarettes can help wean people off regular cigarettes; others believe that they reinforce the smoking habit and increase the user’s exposure to nicotine.

But there’s no dispute that e-cigarettes have grown popular since their introduction in 2004. Now a nationwide survey has found that 10.8 million adults in the United States are vaping.

The analysis, published in the Annals of Internal Medicine, found that 54.6 percent of e-cigarette users were also smoking cigarettes. About 15 percent of vapers had never smoked cigarettes, and 30.4 percent had quit smoking them.

The study is based on data from the Behavioral Risk Factor Surveillance System, a national survey conducted by the Centers for Disease Control and Prevention. In 2016, the researchers surveyed 486,000 people 18 and older by telephone in every state and the District of Columbia, as well as Guam, Puerto Rico and the Virgin Islands.