People who use both vapes and cigarettes are less likely to quit compared to people who only smoke or only vape, according to a study published today (Wednesday) in ERJ Open Research [1].
Instead, the research suggests that over time, most of these 'dual users' tend to revert to only smoking cigarettes.
The researchers say their findings suggest that taking up vaping while continuing to smoke will probably not help people to stop smoking.
The study, by researchers from Germany, the USA and Denmark, was authored by Josef Hamoud from the University Medical Center Göttingen, Germany. It is a systematic review and meta-analysis, meaning researchers reviewed all existing research on people using both vapes and cigarettes and combined the data into one study.
Mr Hamoud said: "Vaping has become widespread among adolescents and adults worldwide. Given the extensive marketing of vapes as healthier alternatives to conventional smoking, they have gained popularity among people trying to quit smoking. Some people are using them in addition to their conventional cigarettes, classifying them as dual users.
"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."
The review brings together 16 individual studies looking at whether groups of dual users went on to quit smoking, switch to vaping only, switch to smoking only or continue dual use over time. The analyses incorporate data on up to 9,337 people including 2,432 dual users.
When researchers compared dual users with people who only smoked cigarettes or only vaped, they found that dual users were less likely to quit completely. Over time, the analysis showed that the majority of dual users reverted to smoking conventional cigarettes.
The proportion of dual users who quit completely was 3% over a period of four to eight months, 5% by eight to 16 months, 13% by 16 to 24 months and 24% by 24 to 48 months. This compares to 6%, 7%, 17% and 25% respectively over the same time periods in people who only smoke and 8%, 19%, 26% and 35% respectively in people who only vape.
Over a period of four to eight months, 30% of dual users switched to cigarettes only. Between eight and 16 months, 47% of dual users switched to cigarettes only. Between 16 and 24 months, the proportion was 58% and after 24 to 48 months, the proportion was 55%.
Most dual users continued to use cigarettes across the time periods. Combining those who continued dual use with those who transitioned to smoking only, the total proportion using cigarettes ranged from 90% to 63%.
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 continued: "Given these findings, we believe that dual use might prove to be a major hinderance 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 say that because they were combining several studies, each with a slightly different approach, it was not possible to categorise different types of dual use, such as people who mostly smoke but occasionally vape.
Mr Hamoud added: "While it may have been argued that heavy smokers might benefit from dual use by reducing their daily cigarette consumption, the high nicotine content of vapes adds to the risk of continued nicotine addiction. Future studies must further stratify dual-use groups to investigate the health implications over time."
Dr Filippos Filippidis is Chair of the European Respiratory Society Tobacco Control Committee, a reader in public health at Imperial College London, UK, and was not involved in the research. He said: "We know that vaping is commonplace and that many people use e-cigarettes as well as cigarettes, often in the hopes of cutting down on smoking or quitting the habit. This large study examined all existing evidence on dual users, and it showed that, for most people, this is not a stepping stone to quitting".
"Nicotine in vapes is highly addictive, so we need to do all we can to discourage non-smokers from starting to vape. E-cigarettes may have a role in smoking cessation for some people, but we need to make sure appropriate support is freely available to help people to quit, as it's clear that many end up being dual users, which can actually undermine smoking cessation attempts."
