"Changes in prevalence of e-cigarette use in England have been positively associated with the success rates of quit attempts. No clear association has been found between e-cigarette use and the rate of quit attempts or the use of other quitting aids, except for NRT obtained on prescription, where the association has been negative".

That was the conclusion of our paper published today in the BMJ (http://www.bmj.com/content/bmj/354/bmj.i4645.full.pdf). This paper, using a time-series approach (see my statistics blog), aimed to estimate how far changes in the prevalence of e-cigarette use in England have been associated with changes in quit success, quit attempts, and use of licensed medication and behavioural support in quit attempts.

This study used data between 2006 and 2015 on 170,490 individuals taking part in the Smoking Toolkit Study (www.smokinengland.info), a representative population survey of adults aged 16+. Around 23% of these were past year smokers and 21% were current smokers. Data were also used on 8,029,012 individuals setting a quit date at stop smoking services.

It was found that for every 1% increase in the prevalence of use of e-cigarettes during a quit attempt, prevalence of successful quit attempts increased by 0.058%. In other words, for every additional 100 smokers using e-cigarettes we would expect around an extra 6 smokers to stop smoking in the short to medium term.

Using these results, we estimated that e-cigarette use during a quit attempt contributed to around an additional 54,288 short to medium term quitters in 2015 compared to no use of e-cigarettes in quit attempts. Given that numerous studies suggest that 2/3rds of smokers generally relapse, this would give an estimate of 18,000 long-term quitters. Although these numbers are small, they are clinically relevant because of the huge health gains from quitting smoking. Of course, it remains possible that relapse among e-cigarette users may be higher or lower than 2/3rds. If it were lower, we would expect many more of the 54,288 to remain smoke free in the long run.

We also found that every 1% increase in the prevalence of use of e-cigarettes among current smokers for any reason was associated with a 0.098% increase in the prevalence of smoking cessation.

An interesting finding, was that the rise in use of e-cigarettes may have contributed to a decline in use of prescription Nicotine Replacement Therapy (NRT) (e.g., the nicotine patch and gum). There are numerous reasons for this, including the possibility that health-care professionals may be discussing e-cigarettes with their clients who are then deciding to use them instead of NRT.

No association was found with attempts to quit smoking, use of prescription medication (i.e. NRT, bupropion or varenicline) or use of NRT over-the-counter. Findings which are consistent with those reported previously (Beard et al Thorax: http://thorax.bmj.com/content/early/2015/07/24/thoraxjnl-2015-206801).

This study had several strengths including the use of a large representative sample of adults from England, the use of time-series analysis which allows one to adjust for the internal structure of the data, underlying trends and seasonality. It also adjusted for a wide range of tobacco control policies, mass media expenditure and smoking prevalence (when looking at the association with the number of smokers setting a quit date at stop smoking services). Of course, it possible that other confounding factors not adjusted for may have played a role and the findings may not be applicable to other countries with less liberal regulatory frameworks for tobacco control and e-cigarettes.

Overall, our findings suggest that e-cigarettes are not undermining attempts to quit smoking at a population level and may be promoting successful attempts to stop. It will be important to continue to carefully monitor associations between e-cigarettes and quitting behaviour, particularly long-term success and relapse.

This paper has been covered by a number of media outlets:
https://www.ft.com/content/ba00f43e-79ab-11e6-97ae-647294649b28
https://www.theguardian.com/society/2016/sep/13/electronic-cigarettes-can-help-smokers-quit-says-study
http://www.bbc.co.uk/news/health-37338992
http://www.dailymail.co.uk/wires/reuters/article-3788183/Scientific-evidence-grows-e-cigarettes-quit-smoking-aids.html
http://www.huffingtonpost.co.uk/entry/e-cigarettes-linked-to-successful-attempts-at-quitting-smoking_uk_57d80745e4b0614ca6be3896
http://www.latimes.com/science/sciencenow/la-sci-sn-electronic-cigarettes-quit-smoking-20160913-snap-story.html
http://www.telegraph.co.uk/science/2016/09/14/e-cigarettes-helped-18000-people-quit-smoking-in-2015-but-long-t/
http://www.thetimes.co.uk/article/vaping-helps-thousands-to-quit-smoking-hmk3vjjrc

According to a new Cancer Research UK report published today, 75% of people in the UK are unaware of the link between obesity and cancer. The nationwide survey found that men from lower socioeconomic backgrounds are even less likely to know about the link. The poorest knowledge of a link was with ovarian, breast and pancreatic cancer, while 60% of those surveyed knew the association with bowl cancer and 55% with liver cancer.

Being overweight or obese is one of the biggest preventable cause of cancer after smoking and is linked to around 18,100 diagnoses each year. A recent report by cancer research UK and the UK Health Forum estimated that if current trends continue, then there will be an estimated additional 670,000 new cancer cases in the next 20 years as a consequence of being overweight and obesity.

Alison Cox, director of prevention at Cancer Research UK, said "It's the governments responsibility to inform the public of the link and also to take action to tackle the obesity epidemic, starting with the health of the nation's children. It's great the Government's childhood obesity plan includes a sugary drink tax, but it's not enough to curb the rising tide of ill-health"

Hooper L, Anderson A, Forster A, Rosenberg G & Vohra J (2015) Public knowledge of the link between obesity and cancer. Cancer Research UK.