Vaping has been endorsed by health experts after the first long-term study of its effects in ex-smokers.
E-cigarettes contain nicotine but not many of the harmful substances produced by smoking tobacco, such as tar or carbon monoxide. However, there has been a debate about exactly how safe their long-term use is.
The study, involving 181 smokers or ex-smokers, has been described as "landmark" as it is thought to be the first (or at least one of the first) looking at long-term vaping outcomes in "real world" users. Previous studies of this kind have mainly relied on laboratory equipment, or animal research, to estimate the long-term effects of e-cigarettes.
The volunteers completed questionnaires and provided breath, saliva and urine samples. The researchers found significantly lower levels of toxic chemicals and cancer-causing substances (carcinogens) in the samples of those of former smokers who had been using e-cigarettes or nicotine replacement therapy (NRT)compared to current smokers.
Another noted result is that current smokers who may be trying to reduce their risk of harm by switching between e-cigarettes and normal cigarettes may be saving money, but doing little for their health. "Combination users" still had very high levels of toxins and carcinogens
This study provides evidence that e-cigarettes and NRT can reduce harm to smokers by reducing exposure to toxic chemicals. The evidence would also seem to support Public Health England’s 2015 report that “E-cigarettes are 95% less harmful than tobacco”.
Where did the story come from?
The study was carried out by researchers from a number of institutions, including University College London, and the Roswell Park Cancer Institute and Centres for Disease Control and Prevention (both in the US). Funding was provided by Cancer Research UK.
The study was published in the peer-reviewed journal: Annals of Internal Medicine.
There has been much discussion over the benefits of vaping over conventional smoking methods and this is the first long-term study assessing these effects. In general the findings have been reported accurately in the UK media; however, none of the limitations, as described by the researchers themselves, have been mentioned.
The Daily Mirror included a quote from professor Kevin Fenton, national director of health and wellbeing at Public Health England, who added: "This study provides further evidence that switching to e-cigarettes can significantly reduce harm to smokers, with greatly reduced exposure to carcinogens and toxins."
What kind of research was this?
This was a cross-sectional study that drew comparisons on exposure to nicotine and other tobacco-related toxins and carcinogens in the following groups:
- current cigarette smokers who only smoked cigarettes
- current cigarette smokers who also used e-cigarettes
- current cigarette smokers who also use other forms of nicotine replacement therapies (NRT), such as skin patches or gum
- former smokers who were now using only e-cigarettes
- former smokers who were now using only NRT
Limitations of this study design include the possibility of recall bias as participants provide information about their smoking habits through a questionnaire. There is also the possibility of residual confounding from other unmeasured factors so findings may not be entirely accurate.
What did the research involve?
The researchers recruited participants from Greater London by placing advertisements in newspapers and online, posters in pharmacies and through marketing companies.
To be able to join the study participants had to be either:
- a current smoker, who has smoked an average of five or more cigarettes per day for at least six months
- a former smoker, who has stopped using tobacco products for at least six months
Researchers aimed to assess the effects of long-term use of non-combustible nicotine delivery – that is NRT or e-cigarettes – for a minimum of six months. They compared:
- current smokers of cigarettes only
- combination smokers – cigarette smokers also using an e-cigarette or NRT
- former smokers using e-cigarettes-only or NRT-only
Participants were asked to visit a laboratory after not eating, drinking, or using combustible cigarettes or other nicotine products for an hour before their visit. During the appointment, the participants filled in a questionnaire including questions on sociodemographic and smoking characteristics.
Breath, saliva, and urine samples were taken, which were assessed for levels of nicotine and other carcinogenic or toxic chemicals.
This included tobacco-specific nitrosamines (TSNAs), which are one of the most important carcinogens in tobacco formed from nicotine. They also looked at a class of toxins called volatile organic compounds (VOCs) such as acrylamide and cyanide-releasing acrylonitrile.
Analyses were adjusted for smoking history, sociodemographic variables, physical health and subjective well-being.
What were the basic results?
A total of 181 participants were included in the study.
Significantly lower levels of cancer-causing chemicals, TSNAs and VOCs were found in samples from former smokers using e-cigarettes only or NRT only, compared with current smokers. Their levels were lower than both those who smoked cigarettes only, or smokers using either e-cigarette or NRT alongside cigarettes.
Former smokers using e-cigarettes only had significantly lower levels of the toxic chemical NNAL (a by-product of exposure to TSNAs) than all other groups. This was equivalent to a 97% reduction compared with the levels of cigarette-only users.
Current smokers of combustible cigarettes only, and current smokers also using NRT or e–cigarettes, had similar levels of the tobacco-related toxins and carcinogens.
Looking at nicotine, levels in urine samples were broadly similar across groups. There was though some variation in salvia levels, with e-cigarette-only users, and those using NRT while continuing to smoke cigarettes had slightly lower nicotine levels than other groups.