People who smoke both vapes and cigarettes are less likely to quit smoking compared to people who use only cigarettes or only vapes, according to a new study published in ERJ Open Research.

Dual users (DU), who smoke both conventional cigarettes (CC) and e-cigarettes (EC), were found to be most likely to revert to smoking only conventional cigarettes over time.

The researchers say the ‘concerning results’ suggest that dual users may be more at risk than people who smoke only conventional cigarettes and show that people who take up vaping whilst still smoking are unlikely to quit smoking conventional cigarettes.

Researchers from Germany, America and Denmark conducted a literature review using PRISMA guidelines and focussed on longitudinal studies that tracked the behaviour of smokers over extended periods.

A total of 46 studies were reviewed, of which eight were suitable for inclusion in the meta-analysis. Studies that reported transitions between dual use, exclusive EC use and exclusive CC use were included.

The reviewers examined how dual users transitioned to either quit smoking, exclusive CC use or exclusive EC use compared to individuals who started as exclusive EC users or exclusive CC smokers. The analysis incorporated data from 9,337 people, including 2,432 dual users.

Baseline dual users who transitioned during the studies were more likely to end up exclusively smoking conventional cigarettes rather than quitting or switching to e-cigarettes only. Dual users were also less likely to quit completely compared to users who were exclusive CC smokers or exclusive EC users.

About 20% of dual users continued to use both EC and CC for 16-24 months, while 8% of dual users did so for 24-48 months, exposing themselves to the potentially harmful dual-use state and associated health risks for longer.

People who vaped exclusively were most likely to quit completely after four to eight months (8%) and 48 months (35%), compared to people who smoked only (6% and 25%, respectively or dual users (3% and 24%) respectively over the same periods.

Josef Hamoud from the University Medical Center Göttingen in Germany said: ‘Given the extensive marketing of vapes as healthier alternatives to conventional smoking, they have gained popularity among people trying to quit smoking.

‘There is still a lot we don’t know about the long-term health effects of vaping. However, credible studies have already delivered concerning results indicating that dual use might be even more harmful than conventional smoking.’

Most dual users continued to use cigarettes across the time periods. Over four to eight months, 30% of dual users switched to cigarettes only. Between 24 to 48 months, the proportion was 55%.

The researchers also point out that over the medium term (eight to 16 months), 38% of dual users were still using both vapes and cigarettes. ‘This cannot be considered a simple ‘transitional state’, but rather a risk for prolonged double exposure,’ Mr Hamoud said.

He added: ‘Given these findings, we believe that dual use might prove to be a major hindrance in achieving smoking abstinence, and this practice should not be recommended for treating nicotine addiction.

‘In addition, while long-term health effects of vapes need to be studied further, the double exposure to large amounts of nicotine and toxicants from both conventional cigarettes and vapes are a great concern for public health.’

The researchers said that while dual use may help heavy smokers reduce the use of conventional cigarettes, the high levels of nicotine in vapes could continue a nicotine addiction. Further studies are needed to investigate the health implications for dual users over time.

A version of this article was first published by our sister title Nursing in Practice