Cohort study of electronic cigarette use: effectiveness and safety at 24 months.
To evaluate the safety and effectiveness of e-cigarettes, by comparing users of only e-cigarettes, smokers of only tobacco cigarettes and dual users.



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



Direct contact and questionnaires by phone or via internet.



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.



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.



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).



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.



NCT01785537.
Department of Medicine and Aging Sciences, University of Chieti, Chieti, Italy.|Local Health Unit of Pescara, Pescara, Italy.|"University G. d'Annunzio" Foundation, Chieti, Italy.|Regional Healthcare Agency of Abruzzo, Pescara, Italy.
Lamberto
L
Manzoli
Department of Medicine and Aging Sciences, University of Chieti, Chieti, Italy.|Local Health Unit of Pescara, Pescara, Italy.
Maria Elena
ME
Flacco
Department "G. F. Ingrassia"-Hygiene and Public Health, University of Catania, Catania, Italy.
Margherita
M
Ferrante
Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy.
Carlo
C
La Vecchia
Department of Public Health Sciences, University of Turin, Turin, Italy.
Roberta
R
Siliquini
Italian National Institute of Health, Rome, Italy.|Institute of Public Health, Università Cattolica del Sacro Cuore, Rome, Largo Francesco Vito, Roma, Italy.
Walter
W
Ricciardi
Department of Public Health and Infectious Diseases, Sapienza University of Rome, Roma, Italy.
Carolina
C
Marzuillo
Department of Public Health and Infectious Diseases, Sapienza University of Rome, Roma, Italy.
Paolo
P
Villari
Department "G. F. Ingrassia"-Hygiene and Public Health, University of Catania, Catania, Italy.
Maria
M
Fiore
D000328:Adult; D000368:Aged; D015331:Cohort Studies; D066300:Electronic Nicotine Delivery Systems / Q000009:adverse effects; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology*; D016540:Smoking Cessation / Q000379:methods*; D011795:Surveys and Questionnaires; D062789:Tobacco Products / Q000009:adverse effects
Cessation; Electronic nicotine delivery devices; Harm Reduction