October 21, 2026

expert reaction to study of vascular function and cardiorespiratory fitness in young adults who vape

Scientists comment on a study of vascular function and cardiorespiratory fitness in young adults who vape, as published in JAMA Cardiology. 

Dr Harry Tattan-Birch, Senior Research Fellow in the Department of Behavioural Science and Health, University College London (UCL), said:

“This small study draws conclusions that its design cannot support. It compares just 17 vapers, 19 smokers and 22 people who use neither at a single point in time, without adequately accounting for other differences between these groups that could explain the findings. Therefore, we cannot know whether the findings reflect effects of vaping itself or other differences between participants. 

“The authors also suggest their findings challenge the idea that vaping is a reduced-harm alternative to smoking from a cardiovascular perspective. This is a serious overinterpretation. Failing to find a statistically significant difference between just 17 vapers and 19 smokers does not mean their effects are equivalent. With such small samples, even substantial differences could easily be missed. Stronger evidence from studies following smokers who switch to vaping has found improvements in the very same measure of blood vessel function reported here, and systematic reviews of population evidence from hundreds of thousands of participants found that cigarette smokers have higher risk of cardiovascular disease and heart attacks compared with people who vape. 

“Vaping is not harmless, and people who do not smoke should not start. But this study cannot establish that vaping caused the differences observed, nor overturn the broader evidence that switching from smoking to vaping likely substantially reduces cardiovascular harm.”

Dr Katie East, Associate Professor in Public Health, Brighton and Sussex Medical School, University of Brighton and University of Sussex, said:

The authors also suggest their findings challenge the idea that vaping is a reduced-harm alternative to smoking from a cardiovascular perspective. This is a serious overinterpretation. Failing to find a statistically significant difference between just 17 vapers and 19 smokers does not mean their effects are equivalent. With such small samples, even substantial differences could easily be missed. Stronger evidence from studies following smokers who switch to vaping has found improvements in the very same measure of blood vessel function reported here, and systematic reviews of population evidence from hundreds of thousands of participants found that cigarette smokers have higher risk of cardiovascular disease and heart attacks compared with people who vape.

Vaping is not harmless, and people who do not smoke should not start. But this study cannot establish that vaping caused the differences observed, nor overturn the broader evidence that switching from smoking to vaping likely substantially reduces cardiovascular harm.”

“This study suffers from several methodological flaws. The research fails to isolate vaping from past smoking history completely, and smoking can have long-lasting cardiovascular and respiratory effects that could have exaggerated any negative impacts attributed to vaping. There were also notable asymmetries in the frequency and intensity of use between the smoking and vaping groups, such that moderate vapers (i.e., those who vape at least five days a week) who could have smoked previously were compared to established daily smokers (i.e., those who smoke at least five cigarettes per day) who had not vaped in the past three months. These criteria contradict the authors’ conclusion regarding “regular daily nicotine vaping in young adults who have never smoked combustible tobacco”, as the recruitment protocol did not mandate daily vaping and permitted those with a history of smoking.

“The research also compares groups with small sample sizes (17-22 people per group) that were poorly matched on some baseline physiological and lifestyle characteristics. There was also substantial variation among participants in each group, indicated by large standard errors for baseline characteristics and outcome measures. The large variation within such small groups makes it difficult to draw reliable or generalisable conclusions about the true effects of vaping versus smoking.

“Currently in Great Britain, only 29% of adults accurately perceive vaping as less harmful than smoking. Overinterpreting such small-scale observational studies can further fuel public misperceptions of vaping, and risks discouraging adults who smoke from transitioning to a less harmful product.”

Prof Peter Hajek, Professor of Clinical Psychology and Director of the Health and Lifestyle Research Unit, Queen Mary University of London (QMUL), said:

“Young people who did not smoke or vape, vapers and smokers were compared in fitness and measures of vascular function that are linked to it. As would be expected, smokers and vapers were less fit and had corresponding vascular function results. Physical inactivity and lower fitness are well known to predate the onset of drug and alcohol use.

“In later life, drugs and alcohol can harm fitness further, and smoking can eventually damage cardiovascular health. However, in this sample of young adults, the finding seems to be just confirming that different lifestyle factors cluster together. The authors correctly acknowledge that the study cannot establish causality, but the press release hints at harms of vaping, something the study did not show.”

Prof Lion Shahab, Professor of Health Psychology and Co-Director of the UCL Tobacco and Alcohol Research Group, University College London (UCL), said:

“While this study reports differences in measures associated with vascular health and cardiorespiratory fitness among people who vape, smoke or use neither product, it is important to interpret these findings in context. As the authors themselves acknowledge, the study cannot establish that vaping causes cardiovascular damage. However, there are several concerns beyond the usual limitations of cross-sectional research.

“First, the study involved a very small sample, including just 17 vapers and 19 smokers, recruited through self-selection from Manchester universities. This raises serious questions about how representative the participants are of the wider population. With such small groups, even one individual with an unusual response can substantially influence the overall findings. It is therefore difficult to draw general conclusions about the relationship between vaping and cardiovascular health.

“Second, the study provides only a snapshot, based on two visits within a single week. This means we cannot know whether the observed differences were caused by vaping or smoking, or whether they reflect pre-existing differences between participants or other factors, including normal day-to-day variation. This is particularly relevant because participants who had never smoked or vaped reported substantially higher levels of physical activity than the other groups. Such differences could plausibly explain at least some of the findings, especially those relating to exercise performance. Other potentially important factors, including medication use and body composition, were also not adequately accounted for in key comparisons.

“Third, the clinical significance of the findings remains uncertain. The measures of blood vessel function used in the study, including flow-mediated dilation and carotid artery reactivity, are not direct measures of cardiovascular disease. Their ability to predict future cardiovascular problems, particularly in otherwise healthy individuals, is limited or not well established. Notably, spirometry, a well-established measure of lung function, showed no differences between groups.

“There are also some puzzling findings. One participant classified as having never used tobacco or nicotine products tested positive for cotinine, indicating nicotine exposure, but was not excluded. Perhaps more surprisingly, the smokers had the most favourable blood lipid profile. These findings further highlight the difficulties of interpreting comparisons between such small, self-selected groups.

“None of this means the study is without value. However, it should be viewed as an exploratory study that raises questions rather than provides firm answers about the cardiovascular effects of vaping. Establishing whether vaping genuinely affects vascular function or cardiorespiratory fitness will require much larger studies following participants over time, ideally including people who start or stop vaping or smoking. Such studies would help distinguish the effects of vaping itself from other differences between individuals and establish whether the observed findings are reliable and clinically meaningful.”

‘Vascular Function and Cardiorespiratory Fitness in Adults Who Use Nicotine Vapes’ by Maxime Boidin et al. was published in JAMA Cardiology at 4pm UK time Wednesday 21 October 2026.

DOI: 10.1001/jamacardio.2026.4626

Declared interests

Katie East: “I have no conflicts of interest to declare.”

Peter Hajek: “No COI”

Lion Shahab: “No COI”