Almost 11 million American adults use e-cigarettes and more than half are under age 35, according to a new study published in the Annals of Internal Medicine. One-third of people who use e-cigarettes vape daily, Reuters reports.

E-cigarette use is most prevalent among men; people who identify as lesbian, bisexual, gay and transgender (LGBT); those who are unemployed; and those with chronic disease. E-cigarette use is also more common among those living in the South and West.

Dr. Nancy Rigotti, Director of the Tobacco Research and Treatment Center at Massachusetts General Hospital, who wrote an editorial accompanying the study, told Reuters, “We know that most e-cigarette users are smokers of conventional cigarettes and that LGBTQ adults are more likely to smoke conventional cigarettes, so I am not surprised that the prevalence of e-cigarette use is higher among LGBTQ individuals.”