Experts Urge Caution Over Study Linking Vaping to Impaired Vascular Function

Scientists have urged caution over a study linking nicotine vaping with impaired blood vessel function and lower fitness in young adults, warning that its small sample cannot establish whether vaping causes cardiovascular damage.

The study, led by Manchester Metropolitan University researchers and published in JAMA Cardiology, found that young adults who vaped had lower average measures of vascular function and cardiorespiratory fitness than people who had never used tobacco or nicotine products. However, independent experts questioned whether the findings could be attributed to vaping itself, highlighting the study's small sample, differences between participants and cross-sectional design.

The research assessed 58 healthy adults with an average age of 26, divided into three groups: 17 exclusive nicotine vape users who had smoked fewer than 100 cigarettes in their lifetime, 19 cigarette smokers who smoked at least five a day with no vaping in the past three months, and 22 people who neither vaped nor smoked, confirmed by urinary cotinine testing. All participants completed two standardized morning visits within one week, including tests of vascular function (flow-mediated dilation and carotid artery reactivity), lung function and cardiorespiratory fitness on a cycle ergometer.

Mean flow-mediated dilation was highest among those who neither vaped nor smoked, at 8.3%, with impairments in the vaping and smoking groups of 5.5% and 4.4% respectively. A similar pattern appeared in carotid artery reactivity. Neither measure differed significantly between the vaping and smoking groups. Peak relative oxygen uptake was lower in the vaping group than in the other two, while measures of ventilation and cardiac output were reduced in both nicotine-using groups. Lung function showed no differences.

Dr Maxime Boidin, senior lecturer in cardiac rehabilitation at MMU and the study's lead author, said the results suggested regular nicotine vaping was associated with changes in vascular function and exercise capacity even among otherwise healthy young adults. He stressed the findings did not mean vaping was as harmful as smoking overall: "If you smoke, switching completely to nicotine vapes markedly reduces the level of exposure to harmful chemicals. If you don't smoke, you should never vape." The researchers acknowledged that the small sample, local volunteer recruitment and cross-sectional design meant they could not establish cause and effect.

Independent experts were sharper. Dr Harry Tattan-Birch of University College London said the study "draws conclusions that its design cannot support," noting it compares 17 vapers, 19 smokers and 22 others at a single point in time without adequately accounting for other differences between the groups. He called the suggestion that the results challenge vaping as a reduced-harm alternative "a serious overinterpretation," adding that failing to find a significant difference between such small groups does not mean their effects are equivalent.

Dr Katie East of Brighton and Sussex Medical School raised concerns about recruitment criteria, noting the groups differed in frequency and intensity of use and were poorly matched on baseline characteristics. With only 29% of adults in Great Britain accurately perceiving vaping as less harmful than smoking, she warned that overinterpreting such small observational studies "can further fuel public misperceptions of vaping, and risks discouraging adults who smoke from transitioning to a less harmful product."

Professor Peter Hajek of Queen Mary University of London suggested the results could reflect pre-existing lifestyle and fitness differences, and said the press release hinted at harms the study did not show. Professor Lion Shahab of UCL described the findings as exploratory, noting that the vascular measures used are not direct indicators of cardiovascular disease, that one participant classified as a never-user tested positive for cotinine, and that the smokers had the most favourable blood lipid profile. He called for larger longitudinal studies before firm conclusions are drawn.

The study was funded by a Cardiovascular Research Grant from Manchester Academic Health Science Centre – Health Innovation Manchester.

[Reference]
- Vape Business (original report) — https://www.vapebusiness.biz/scientists-challenge-vaping-heart-study/
- Science Media Centre, expert reaction (Oct. 21, 2026) — https://www.sciencemediacentre.org/expert-reaction-to-study-of-vascular-function-and-cardiorespiratory-fitness-in-young-adults/
- TCTMD coverage — https://www.tctmd.com/news/early-signs-vascular-cardiorespiratory-problems-seen-regular-vape-users
- Asian Trader coverage (Oct. 26, 2026) — https://www.asiantrader.biz/vaping-cardiovascular-fitness-experts-caution