Are e-cigarettes more harmful than regular cigarettes?

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The use of electronic cigarettes (e-cigarettes) has grown in recent years in part because of a belief that their use is safer than conventional cigarettes, or that they may be helpful for quitting tobacco use. However, the effects of e-cigarettes on the oral microbiome are not well-studied.

Therefore, researchers from Ohio sought to investigate how the use of e-cigarettes may change the subgingival microbiome. Their results suggest that smoking e-cigarettes is not a safe alternative to smoking regular cigarettes, and it may be a risk factor for periodontal disease. The findings were presented on March 24 in a poster at the International Association for Dental Research (IADR) meeting in San Francisco.

“Using e-cigarettes to quit smoking is not helping your microbiome.”
— Purnima Kumar, PhD, DDS

"Using e-cigarettes to quit smoking is not helping your microbiome," Purnima Kumar, PhD, DDS, a professor at Ohio State University College of Dentistry and one of the study's authors, told

The lead author, Sukirth Ganesan, is a doctoral candidate at Ohio State University.

A new risk factor?

Electronic nicotine delivery systems, or e-cigarettes, are battery-operated, and when puffed on they deliver a heated aerosol containing a mixture of nicotine, propylene glycol (and/or glycerol), and flavor.

The same scientific team previously found that smoking cigarettes leads to dysbiotic oral biofilms that are commensal-poor and rich in pathogens, and that it increases susceptibility to periodontitis.

In the current study, the researchers collected subgingival plaque samples from 100 periodontally and systemically healthy individuals from the following five groups:

  • E-cigarette users
  • Cigarette smokers
  • Users of both e-cigarettes and conventional cigarettes
  • Former cigarette smokers who use e-cigarettes
  • Controls

They conducted whole-genome shotgun sequencing and validated the findings using an in vitro biofilm model.

Sukirth Ganesan and Dr. Purnima Kumar present their research on e-cigarettes at IADR 2017.Sukirth Ganesan and Dr. Purnima Kumar present their research on e-cigarettes at IADR 2017.

In the e-cigarette microbiome, they identified 8,879 functionally annotated genes. Of these, more than a third were found in all individuals who were e-cigarette users, users of both e-cigarettes and regular cigarettes, and former cigarette smokers who were e-cigarette users. There were 1,353 genes unique to these three groups that encoded for antibiotic resistance, motility chemotaxis, stress response, horizontal gene transfer, cell wall, iron acquisition, and membrane transport. The authors said these functionalities were encoded by some known pathogens, as well as some uncultivated species.

In contrast, the current cigarette smokers and controls shared no more than 15% of genes with e-cigarette users.

"E-cig users were functionally and taxonomically distinct from both smokers and nonsmokers," the authors wrote.

Harm could be greater

The results do not indicate that smoking e-cigarettes is less harmful than smoking conventional cigarettes, and they suggest that smoking e-cigarettes could be a risk factor for periodontal disease, according to Dr. Kumar and colleagues.

"The risk for harm associated with e-cigs may be similar to or greater than smoking," they wrote.

The use of e-cigarettes has an effect on the microbiome that is distinct from that of tobacco smoke, they concluded.

"The similarity in the microbiomes of former, current, or never smokers who use e-cigs does not support the hypothesis that e-cigs promote harm reduction in cigarette smokers," they wrote. "The pathogen and virulence enrichment observed in clinically healthy individuals might augur the emergence of a new risk factor for periodontal disease."

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