Electronic cigarette effectiveness and safety at 24 months: a cohort study

Background To evaluate e-cigarette long-term safety and effectiveness, by comparing users of e-cigarettes only (E-CIG), smokers of tobacco cigarettes only (TOB), and dual users (DUAL). Methods Prospective cohort study. We update previous findings (NCT01785537) and report the results of the 24-month follow-up. Data were collected through direct contact and questionnaires by phone or via internet. Adults (30-75 years) were classified as: (a) tobacco smokers, if they smoked 1 tobacco cigarette/day, (b) e-cigarette users, if they inhaled 50 puffs/week of any type of e-cigarette, (c), dual users, if they smoked tobacco cigarettes and also used e-cigarettes. Carbon monoxide levels were tested in 50% of those declaring tobacco smoking abstinence. Hospital discharge data were used to validate possibly-related serious adverse events in 46.0% of the sample. Main outcome measures were: sustained abstinence from tobacco cigarettes and/or e-cigarettes after 24 months, reduction in the number of tobacco cigarettes smoked daily, possibly-related serious adverse events. Results Data at 24 months were available for 229 E-CIG, 480 TOB, and 223 DUAL. 61.1% of E-CIG remained abstinent from tobacco (while 23.1% and 26.0% of TOB and DUAL achieved tobacco abstinence). Self-rated health, adverse events, and the rate (18.8%) of stopping use of either product (tobacco and/or ecigarettes) did not differ significantly across all groups. Most DUAL at baseline abandoned e-cigarettes and continued to smoke tobacco. Those who continued dual-using or converted from tobacco smoking to dual-use experienced significant improvements in the 3 outcomes compared to those who continued or switched to only smoking tobacco (p < 0.001). Conclusions E-cigarette use alone might support tobacco quitters remaining abstinent from smoking. Dual use did not improve the likelihood of quitting tobacco or e-cigarette use, but may be helpful to reduce tobacco consumption. Adverse event data must be considered preliminary. Key messages: After 24 months of a prospective follow-up, most users of ecigarettes alone were able to remain abstinent from tobacco smoking Dual use of e-cigarettes with tobacco cigarettes did not encourage quitting tobacco or e-cigarette use, but may be helpful to reduce tobacco consumption.