The use of electronic cigarettes as a tool for smoking cessation led to short-term success, but the effect was not sustained over time, a systematic literature review found.
At 1 month, the rate of smoking abstinence was significantly greater for e-cigarettes than placebo (RR 1.71, 95% CI 1.08-2.72, I2=0%), according to Matthew Stanbrook, MD, PhD, of the University of Toronto.
However, the significant difference was no longer present at 3 months (RR 1.95, 95% CI 0.74-5.13, I2=65%) or 6 months (RR 1.32, 95% CI 0.59-2.93, I2=59%), he reported during a press conference at the annual meeting of the American Thoracic Society here.
“Electronic cigarettes are battery-powered electronic nicotine delivery devices designed to deliver nicotine in a similar manner to tobacco without tobacco’s other harmful constituents, but their overall safety is uncertain,” he said.
To address this question, he and his colleagues conducted a systematic review of the literature through May 2014, identifying four studies for inclusion — two randomized trials and two uncontrolled before-and-after studies.
The only study that evaluated continuous abstinence found rates of only 7.3% and 4.1% for e-cigarettes and placebo at 6 months (RR 1.77, 95% CI 0.54-5.77, a difference that was not statistically significant.
In that study, there also was no difference in rates of abstinence at 6 months between e-cigarettes and the open-label nicotine patch use (7.3% versus 5.8%, RR 1.26, 95% CI 0.68-2.34), Stanbrook reported.
Respiratory adverse events among e-cigarette users included dry cough, with an incidence of 26% to 32%, irritation of the throat, in 7% to 32%, and shortness of breath, in 2% to 20%. The incidence of these events tended to decline with longer use.
There have been case reports of serious adverse events associated with e-cigarette use, including recurrent atrial fibrillation, lipid pneumonia, relapse of ulcerative colitis, and death, “and bear in mind that our time frame is limited,” he said.
The incidence of serious adverse events was not significantly different between e-cigarettes and placebo e-cigarettes, at 19.7% and 13.9% (RR 1.36, 95% CI 0.54-3.42), but occurred significantly more often than with the nicotine patch, at 19.7% versus 11.8% (RR 1.97, 95% CI 1.05-3.68).
“Given the paucity of existing data on the safety and efficacy of e-cigarettes, longer term studies are needed to clarify their possible role in smoking cessation,” he concluded.