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Electronic cigarettes can help people quit smoking - but more evidence needed on long-term harms

Published: 14 October 2020

Newly updated Cochrane evidence published today in the Cochrane Library finds that electronic cigarettes containing nicotine could increase the number of people who stop smoking compared to nicotine replacement therapy.

Smoking is a significant global health problem. Many smokers want to quit, but find giving up long term difficult. One of the most effective and widely used ways is to combat the cravings associated with nicotine addiction by delivering nicotine through patches and chewing gum.

Electronic cigarettes have increased in popularity recently, and they have begun to look and feel less like conventional cigarettes. Unlike chewing gum and patches, they mimic the experience of cigarette smoking as they are hand-held and generate a smoke-like vapour. This helps to recreate sensations similar to smoking without exposing users or other people to smoke from conventional cigarettes, and can be used to provide smokers with nicotine.

A team of researchers have updated a Cochrane Review comparing the effects of electronic cigarettes with other ways of delivering nicotine – such as patches and chewing gum - or with dummy electronic cigarettes that do not contain nicotine, or no treatment. The updated review includes 50 studies - 35 more than its last publication in 2016. Of these, 24 are uncontrolled studies, but their results support the data from the randomised controlled trials.

The researchers identified three studies, in 1,498 people, that compared nicotine-containing electronic cigarettes with nicotine replacement therapy given as patches or gum. Results showed that more people quit smoking if they used electronic cigarettes containing nicotine compared to other forms of nicotine replacement. If six people in 100 quit by using nicotine replacement therapy, 10 people in 100 would quit by using electronic cigarettes containing nicotine, meaning an additional four people in 100 could potentially quit smoking with nicotine containing electronic cigarettes.

Similar results were seen in another three studies, involving 802 people, comparing nicotine-containing electronic cigarettes with electronic cigarettes not containing nicotine.

Evidence from four studies (2,312 people) showed more people using nicotine-containing electronic cigarettes quit smoking than those receiving only behavioural support or no support. If four people in 100 quit with no support, an additional six people in 100 might quit by using nicotine electronic cigarettes.

The review authors did not detect any clear evidence of serious harms from nicotine electronic cigarettes. However, evidence about serious harms is uncertain because the overall number of studies was small and serious health problems were very rare in both users and non-users of nicotine electronic cigarettes. There was no information about the effects of long-term use (more than two years) of nicotine-containing electronic cigarettes. The studies showed that throat and mouth irritation, headache, cough, and nausea are the most commonly reported side effects in the short- to medium-term (up to two years). The studies assessed the potential harms of electronic cigarettes when used to help smokers quit, so did not assess other potential harms such as whether electronic cigarettes encourage nicotine use among non-smokers.

Lead author of the updated Cochrane Review, Jamie Hartmann-Boyce from the Cochrane Tobacco Addiction Group, said:

“The randomised evidence on smoking cessation has increased since the last version of the review and there is now evidence that electronic cigarettes with nicotine are likely to increase the chances of quitting successfully compared to nicotine gum or patches.

“Electronic cigarettes are an evolving technology. Modern electronic cigarette products have better nicotine delivery than the early devices that were tested in the trials we found, and more studies are needed to confirm whether quit rates are affected by the type of electronic cigarettes being used.

“While there is currently no clear evidence of any serious side effects, there is considerable uncertainty about the harms of electronic cigarettes and longer-term data are needed. Scientific consensus holds that electronic cigarettes are considerably less harmful than traditional cigarettes, but not risk-free.

“It’s important that the review continues to provide up-to-date information to people who smoke, healthcare providers and regulators about the potential benefits and harms of electronic cigarettes.”

The Cochrane Tobacco Addiction Review Group is one of 21 NIHR-funded Cochrane Review Groups in the UK producing systematic reviews providing important evidence to help the NHS adopt the most effective and best-value treatments. 

More information on the review is on the Cochrane website.

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