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Cohort study of electronic cigarette use: effectiveness and safety at 24 months
  1. Lamberto Manzoli1,2,3,4,
  2. Maria Elena Flacco1,2,
  3. Margherita Ferrante5,
  4. Carlo La Vecchia6,
  5. Roberta Siliquini7,
  6. Walter Ricciardi8,9,
  7. Carolina Marzuillo10,
  8. Paolo Villari10,
  9. Maria Fiore5
  10. the ISLESE Working Group
    1. 1Department of Medicine and Aging Sciences, University of Chieti, Chieti, Italy
    2. 2Local Health Unit of Pescara, Pescara, Italy
    3. 3“University G. d'Annunzio” Foundation, Chieti, Italy
    4. 4Regional Healthcare Agency of Abruzzo, Pescara, Italy
    5. 5Department “G. F. Ingrassia”—Hygiene and Public Health, University of Catania, Catania, Italy
    6. 6Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy
    7. 7Department of Public Health Sciences, University of Turin, Turin, Italy
    8. 8Italian National Institute of Health, Rome, Italy
    9. 9Institute of Public Health, Università Cattolica del Sacro Cuore, Rome, Largo Francesco Vito, Roma, Italy
    10. 10Department of Public Health and Infectious Diseases, Sapienza University of Rome, Roma, Italy
    1. Correspondence to Dr Lamberto Manzoli, Palazzina di Odontoiatria, University of Chieti, Via dei Vestini 5, Chieti 66100, Italy; lmanzoli{at}


    Objective To evaluate the safety and effectiveness of e-cigarettes, by comparing users of only e-cigarettes, smokers of only tobacco cigarettes and dual users.

    Design Prospective cohort study. We update previous 12-month findings and report the results of the 24-month follow-up.

    Data sources Direct contact and questionnaires by phone or via internet.

    Methods Adults (30–75 years) were classified as: (1) tobacco smokers, if they smoked ≥1 tobacco cigarette/day, (2) e-cigarette users, if they inhaled ≥50 puffs/week of any type of e-cigarette and (3) 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 Sustained abstinence from tobacco cigarettes and/or e-cigarettes after 24 months, the difference in the number of tobacco cigarettes smoked daily between baseline and 24 months, possibly related serious adverse events.

    Results Data at 24 months were available for 229 e-cigarette users, 480 tobacco smokers and 223 dual users (overall response rate 68.8%). Of the e-cigarette users, 61.1% remained abstinent from tobacco (while 23.1% and 26.0% of tobacco-only smokers and dual users achieved tobacco abstinence). The rate (18.8%) of stopping use of either product (tobacco and/or e-cigarettes) was not higher for e-cigarette users compared with tobacco smokers or dual users. Self-rated health and adverse events were similar between all groups. Among those continuing to smoke, there were no differences in the proportion of participants reducing tobacco cigarette consumption by 50% or more, the average daily number of cigarettes and the average self-rated health by baseline group. Most dual users at baseline abandoned e-cigarettes and continued to smoke tobacco. Those who continued dual using or converted from tobacco smoking to dual use during follow-up experienced significant improvements in the 3 outcomes compared with 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. However, 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 were scarce and must be considered preliminary.

    Trial registration number NCT01785537.

    • Electronic nicotine delivery devices
    • Cessation
    • Harm Reduction

    This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:

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