LA JOLLA (CNS) - Users of electronic cigarettes are less likely to quit  smoking than smokers who never use the devices, the UC San Diego School of  Medicine reported Thursday.

   In a study published in the American Journal of Public Health, UCSD  researchers found that smokers who used e-cigarettes -- also known as vapor  inhalers -- were 49 percent less likely to decrease cigarette use and 59  percent less likely to quit altogether, compared to smokers who never used e- cigarettes.

   The population-based study followed 1,000 California smokers over one  year, according to UCSD. The results come amid a debate over the effectiveness  of the battery-operated devices.

   "Based on the idea that smokers use e-cigarettes to quit smoking, we  hypothesized that smokers who used these products would be more successful in  quitting," said Dr. Wael Al-Delaimy, a professor and chief of the Division of  Global Public Health in the Department of Family Medicine and Public Health.

   "But the research revealed the contrary," Al-Delaimy said. "We need  further studies to answer why they cannot quit. One hypothesis is that smokers  are receiving an increase in nicotine dose by using e-cigarettes."

   The scientists said that although e-cigarettes do not contain tobacco,  users exhale a mixture of volatile organic compounds, heavy metals and ultra- fine particles that usually contain aerosolized nicotine in a cloud of vapor.

   The findings show that daily smokers and women were more likely to have  tried e-cigarettes.

   Al-Delaimy said the study could inform the U.S. Food and Drug  Administration and other regulators on the profile of e-cigarette usage among  smokers as they create guidelines for the devices.

   The county and city of San Diego last year approved restrictions on the  sale and use of e-cigarettes last year, placing them in roughly the same  category as traditional cigarettes.

   The Veterans Affairs San Diego Healthcare System and San Diego State  University also took part in the study, which was partially funded by the  California Department of Public Health.