Knowing the risks

A BMJ review of e-cigarettes’ effects shows concerning results including higher rates of acute respiratory illness, acute injury to the small airways and immunosuppression

Studies show e-cigarettes have measurable adverse biologic effects on organ and cellular health, according to a new comprehensive international review published in the BMJ.

The long-term health effects of exposure to e-cigarettes, especially of chronic exposure, are currently uncertain, say top researchers from the University of California San Francisco, the Yale School of Medicine, the University of Southern California and the University of North Carolina in the US.

Additionally their effectiveness as a smoking cessation intervention and their impact at a population level remain “highly controversial”.

However their review found evidence that e-cigarettes, which use a metal resistance coil to heat and aerosolise mixtures of vegetable glycerine, propylene glycol, nicotine and flavouring agents, have direct effects on the respiratory and immune systems.

E-cigarettes emit volatile carbonyls, reactive oxygen species, furans and metals (nickel, lead and chromium), many of which are toxic to the lung, according to this report by the National Academies of Sciences, Engineering and Medicine.

In population studies, users have reported several negative symptoms involving the nose, mouth, throat and airways.

Studies of adolescents across various countries have found e-cigarette use was associated with increased odds of reporting chronic cough or phlegm, a nearly twofold increase in the risk of chronic bronchitic symptoms (chronic cough, phlegm, or bronchitis), and increased risk of self-reported diagnosis of asthma by a doctor in the previous year.

E-cigarette use among young people is accelerating, with one study finding prevalence in the US in 2018 was a whopping 20% among 10th grade students and 25% among 12th grade students.

Across nearly 40,000 participants in the Health eHeart Study, e-cigarette use was associated with higher self rating of shortness of breath and reports of COPD and asthma.

“The consistency of these associations among both young and adult e-cigarette users suggest that e-cigarette users experience symptoms of both airway and alveolar injury, which are consistent with the studies of human and animal lungs,” say the researchers.

Meanwhile, in the past year several hundred cases of acute respiratory illness associated with e-cigarette use have been reported in the US, along with eight deaths.

The majority of affected vapers have presented with respiratory and gastrointestinal symptoms, with some diagnosed as having acute respiratory distress syndrome.

Whether this novel syndrome is caused by propylene glycol or vegetable glycerine and nicotine, or is due to tetrahydrocannabinols and associated solvents and adulterants, is yet to be determined.

However similar cases have been found in the UK and Japan, which suggests it has the potential to be a more widespread phenomenon, say the researchers.

Further controlled study results “suggest that e-cigarettes may cause acute, physiologically detectable injury to the small airways.

“Because of the delicate nature of the lungs, even mild inflammation can be damaging,” they say.

A rapidly increasing number of case reports link e-cigarette use to severe inflammatory diseases affecting the small airways and alveoli, such as lipoid pneumonia, eosinophilic pneumonia, diffuse alveolar haemorrhage, organising pneumonia, respiratory bronchiolitis, associated interstitial lung disease, and hypersensitivity pneumonitis.

Nasal scrape biopsies also show extensive immunosuppression at the gene level with e-cigarette use, while reports by e-cigarette users suggest increased susceptibility to and/or delayed recovery from respiratory infections.

Due to a lack of long-term vaping safety studies, saying with certainty that e-cigarettes are safer than combustible cigarettes is “impossible”, say the authors.

Therefore they suggest use of evidence-based pharmacotherapy and nicotine patches combined with counselling as the best approach for health practitioners in guiding people to quit smoking.

“Smokers and ex-smokers using e-cigarettes should be provided with clear information on the uncertainties about health risks and harm reduction and encouraged to participate in complementary counselling using established approaches, with a goal of quitting all tobacco products and ultimately reducing nicotine dependency as soon as possible,” they say.

Meanwhile “for young people, prevention is key.”

Read the full review here

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