Electronic cigarettes: assessing the efficacy and the adverse effects through a systematic review of published studies.

BACKGROUND: To investigate the efficacy and the adverse effects (AEs) of the electronic cigarette, we performed a systematic review of published studies. METHODS: We selected experimental and observational studies examining the efficacy (as reduction of desire to smoke and/or number of cigarettes smoked and/or quitting or as reduction of nicotine withdrawal symptoms) and the safety of EC (AEs self-reported or clinical/laboratory). The following search engines were used: PubMed, ISI Web of Knowledge and Cochrane Controlled Trials Register. RESULTS: Finally, six experimental studies and six cohort studies were included. In the prospective 12-month, randomized controlled trial, smoking reduction was documented in 22.3 and 10.3% at Weeks 12 and 52, respectively (P < 0.001 versus baseline). Moreover, two cohort studies reported a reduction in the number of cigarette/day (from 50 to 80%) after the introduction of the EC. 'Mouth and throat irritation', 'nausea', 'headache' and 'dry cough' were the most frequently AEs reported. CONCLUSIONS: The use of the EC can reduce the number of cigarettes smoked and withdrawal symptoms, but the AEs reported are mainly related to a short period of use. Long-term studies are needed to evaluate the effects of the EC usage after a chronic exposure.