A recent study involving over 4.5 million participants indicates that smokers who switch to vaping after quitting cigarettes are more than 50% more likely to develop lung cancer compared to those who successfully quit smoking altogether. However, it still underscores that e-cigarettes may present less risk than continuing to smoke.

“This study contributes to a growing body of evidence indicating that e-cigarettes are not as low-risk as previously believed,” says Becky Freeman from the University of Sydney, Australia, who was not involved in the research. “[It’s] crucial for those attempting to quit smoking to seek safer options first, and only use e-cigarettes after exhausting other methods.”

In the UK by 2024, over 40% of smokers who quit are expected to use e-cigarettes. Notably, 20% of ex-smokers were still vaping more than a year after quitting. Although many advocate for e-cigarettes as an effective smoking cessation tool, they have been associated with airway inflammation, reduced lung function, and even lung cancer in animal studies.

To further investigate the effects of e-cigarettes, Kim Young Wook and researchers from Seoul National University followed more than 4.5 million adult smokers as part of South Korea’s National Health Checkup Program from 2018 to 2023.

Participants were categorized as current smokers, short-term quitters (those who hadn’t smoked since at least 2018), or long-term quitters (those who hadn’t smoked since at least 2014). Over the study period, 35,887 participants developed lung cancer, with 12,807 related deaths recorded.

Analysis of this data revealed that ex-smokers who vape are at a significantly greater risk of lung cancer death compared to their counterparts who stopped smoking completely. “Ex-smokers who continued vaping faced a 56% higher risk of lung cancer,” Kim stated.

While long-term studies are essential, some chemicals found in e-cigarettes have been associated with DNA damage. Vaping has also been linked to oxidative stress, meaning an imbalance between free radicals and antioxidants in the body, as well as epigenetic changes affecting genes and inflammation of respiratory and oral tissues.

Nonetheless, Kim and his team emphasize that they cannot definitively conclude that e-cigarettes cause lung cancer, and that further research is warranted, especially in populations outside of South Korea.

Remarkably, ex-smokers who vape experienced a significantly lower risk of death from all causes in comparison to active smokers, reinforcing the broader health benefits of quitting smoking altogether.

Nicole Lee from Curtin University in Perth, Australia, pointed out that the study’s findings suggest that completely quitting both smoking and vaping is more effective for preventing lung cancer than continuing to vape while attempting to quit smoking. “The results of this study are vital for individuals who have quit smoking,” she emphasized.

“Our recommendation to smokers remains that the safest choice is to quit entirely, but if quitting is challenging, [without the use of e-cigarettes] or if they prefer not to use them, transitioning to e-cigarettes is a safer alternative,” Lee stated. “As a harm reduction strategy, it certainly is preferable to continuing to smoke.”

Professor Bernard Stewart from the University of New South Wales in Sydney added that further research is necessary before implementing public health policies that may impose additional restrictions on e-cigarettes.