Heart harm claims from study of just 17 vapers challenged by experts

Experts have challenged claims about vaping’s harm to the heart after a study involving just 17 vapers raised concerns about blood vessel function and fitness.

Four researchers responding through the Science Media Centre questioned how far the findings could be taken, warning that the study could neither establish that vaping caused damage nor show it was as harmful as smoking.

Dr Harry Tattan-Birch, a senior research fellow at University College London (UCL), said: “This small study draws conclusions that its design cannot support.”

What the study found

The research, published in JAMA Cardiology on 21 October, compared 17 vapers, 19 smokers and 22 people classed as non-users. Their average age was 26.

Participants underwent blood vessel, lung and exercise tests. Both vapers and smokers recorded poorer results on two measures of how arteries respond than non-users.

Vapers also had lower peak oxygen uptake during exercise, a measure of fitness. Lung function showed no significant difference between the groups.

The researchers concluded that vaping was associated with poorer blood vessel function and fitness. But the study compared different people at one point in time, leaving uncertainty about what caused those differences.

A smoking comparison under fire

Tattan-Birch challenged the suggestion that the results weaken the case for vaping as a less harmful alternative to cigarettes.

“The authors also suggest their findings challenge the idea that vaping is a reduced-harm alternative to smoking from a cardiovascular perspective,” he said. “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.”

He pointed to research following smokers who switched to vaping, which had found improvements in the same blood vessel measure used in this study.

“Vaping is not harmless, and people who do not smoke should not start,” he said. “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.”

Previous smoking clouds the picture

Dr Katie East, associate professor in public health at Brighton and Sussex Medical School, questioned whether the study had adequately separated vaping from previous smoking.

“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,” she said.

The recruitment criteria allowed vapers who had smoked fewer than 100 cigarettes in their lifetime. That leaves scope for previous smoking, despite the conclusion describing them as never-smokers.

East also highlighted differences in smoking and vaping frequency, and variation within the small groups.

She said: “The large variation within such small groups makes it difficult to draw reliable or generalisable conclusions about the true effects of vaping versus smoking.”

Test results cannot establish heart disease

Professor Lion Shahab, professor of health psychology at UCL, said participants had volunteered from Manchester universities, raising questions about how well they represented the wider population.

“With such small groups, even one individual with an unusual response can substantially influence the overall findings,” he said.

The assessment covered two visits within a single week. Shahab said this could not establish whether differences existed before participants began vaping or smoking.

He also questioned what the blood vessel measurements could reveal about future illness.

“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,” he said.

Calls for longer-term research

Professor Peter Hajek, professor of clinical psychology at Queen Mary University of London, said lifestyle differences offered another possible explanation.

He said: “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.”

Shahab said the research had value as an exploratory study, while calling for larger investigations tracking people over time, including those who start or stop smoking or vaping.

The study’s authors also called for follow-up research. Their conclusion stated: “These findings highlight the need for longitudinal studies to determine long-term clinical implications.”