A study of young people has found just 16 puffs of a nicotine-free e-cigarette can cause a major drop in blood flow to the main artery of the leg, something the authors say mimics the effects of aging. Electronic cigarettes use a hot metal element to turn an e-liquid, with or without nicotine, into an aerosol that is inhaled. It’s called vaping, and is seen by some as safer than traditional smoking because no tobacco is burned.
It is also getting popular with teens. The US Centres for Disease Control and Prevention report 1.5 million more high school students vaping in 2018 compared to the previous year, a 71% surge.
The study’s authors, led by Felix Wehrli from the University of Pennsylvania, US, were spurred by data suggesting non-nicotine elements in the vaping aerosol are more toxic than people might think.
E-liquids contain propylene glycol and glycerol which, at room temperature, form lung-irritants called acetals. The aerosol also has ultrafine metal particles from the heating element that cause oxidative stress a whole-body inflammation linked to a plethora of illnesses including cancer.
Standard tobacco smoking damages blood vessels – the flexible tubes carrying blood around the body – causing stroke, heart attacks and sometimes amputated limbs.
Wehrli’s team wanted to see how those blood vessels fared in the face of a vaping challenge. They enlisted 31 non-smokers, with an average age of 24, to have MRI scans measure the blood flow in their leg and aorta – the big artery coming out of the heart – before and after puffing on a nicotine-free, tobacco-flavoured e-cigarette.
The measurements were done after releasing a tourniquet from the leg which caused a surge of blood into the oxygen-starved limb, a phenomenon called “reactive hyperaemia”.
The results may well prompt a re-think for people who think e-cigarettes are a safe option.
Blood velocity in the leg’s major artery dropped by a largish 17% after vaping. Dilation of the same vessel was down 34% after the e-cig. On top of all that, the speed at which blood flow returned to normal after release of the cuff fell by 26% post-puff.
“The alterations in reactive hyperaemic response parallel those observed in older people because of physiologic aging,” the authors write. Even the aorta – which became marginally stiffer – was affected.
Not that changes were confined to the big vessels. Blood returning from the leg carried 20% less oxygen after vaping, suggesting more was eaten up in the small vessels due to slow flow.
The authors pull few punches in appraising their findings.
“E-cigarettes are advertised as not harmful, and many e-cigarette users are convinced that they are just inhaling water vapor,” says the study’s lead author Alessandra Caporale, also of UPenn.
“But the solvents, flavourings and additives in the liquid base, after vaporisation, expose users to multiple insults to the respiratory tract and blood vessels.”
The findings suggest vaping impacts cells lining the blood vessels called the endothelium, which control vessel diameter and blood flow. Long term damage to the endothelium triggers the strokes and heart attacks seen in tobacco smokers.
“We’ve shown that vaping has a sudden, immediate effect on the body’s vascular function, and could potentially lead to long-term harmful consequences,” says Wehrli.
“Clearly if there is an effect after a single use of an e-cigarette, then you can imagine what kind of permanent damage could be caused after vaping regularly over years.”
The study appears in the journal Radiology.
Related reading: Researchers link vaping to risk of oral disease
Paul Biegler is a philosopher, physician and Adjunct Research Fellow in Bioethics at Monash University. He received the 2012 Australasian Association of Philosophy Media Prize and his book The Ethical Treatment of Depression (MIT Press 2011) won the Australian Museum Eureka Prize for Research in Ethics.
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