E-cigarette use is considered a less harmful alternative to smoking. However, more and more studies show that e-cigarettes also have numerous negative effects on health. A new study now suggests that the oral flora of “vapers” has changed in favor of harmful microorganisms. The bacterial communities in the mouths of e-cigarette users have been linked to an increased risk of gum diseases such as periodontitis. They are similar to smokers, but also have unique characteristics.
E-cigarettes are often seen as less harmful than traditional cigarettes. Instead of burning tobacco, they vaporize a mixture of water with propylene glycol and glycerin, usually with added nicotine and various flavorings. But even if the alleged lower health risk is an argument for many users to “vape” rather than smoke, there is increasing evidence that e-cigarettes also have numerous negative effects on health.
Comparison of smokers, vapers and non-smokers
A team led by Scott Thomas from the New York University College of Dentistry has now investigated how e-cigarettes affect the oral flora. To do this, the researchers took plaque samples from 27 smokers, 28 “vapers” and 29 non-smokers and analyzed the microbial communities they contained. In addition, all subjects underwent a dental examination. Only people who already showed signs of periodontitis were included in the study. In this gum disease caused by bacteria, the gums are chronically inflamed, tend to bleed and recede more and more. In order to record the course of the disease in the different groups, the researchers took another sample after six months and examined the condition of the teeth and gums of the study participants.
“Our data suggest that e-cigarette use promotes a stable periodontal microbiome, intermediate between that of conventional cigarette smokers and nonsmokers, with unique characteristics that may affect host oral health in different ways than conventional cigarette use,” write the researchers. They found certain groups of bacteria in all test subjects, while others only in smokers, vapers or non-smokers. The oral microbiome of the vapers was more similar to that of the smokers than that of the non-smokers, but also harbored bacterial communities that were not found in either of the other two groups.
aggravation of periodontal disease
Periodontal disease worsened in some of the study participants between the first and second visits. In the first examination, there were three people in the vaping group who only suffered from mild periodontal disease. At the second examination, her disease had progressed to what was classified as a moderate stage. One vaper and four each of smokers and non-smokers previously diagnosed with moderate periodontal disease had severe periodontal disease at the second visit.
Since the severity of the disease was not evenly distributed across the groups at the beginning of the study – there were no subjects in the smoker group from the start with only mild periodontal disease – these results cannot be compared directly. In addition, the groups differed in terms of demographic characteristics such as age, gender and ethnicity, so that the use of cigarettes or e-cigarettes is just one of many possible influencing factors.
Oral flora and immune modulators changed
However, analyzes of the microorganisms in the plaque deposits at least provide evidence that smoking and vaping may actually play a role in the progression of the disease. Several genera of bacteria, including Selenomonas, Leptotrichia, and Saccharibacteria, were significantly more common in both smokers and vapers than non-smokers. Several other bacteria — including Fusobacterium and Bacteroidales, which are known to be associated with gum disease — were particularly dominant in the mouths of e-cigarette users.
The researchers also found that certain messenger substances of the immune system, so-called cytokines, differed in smokers, vapers and non-smokers. TNFα, a cytokine that causes inflammation, was significantly elevated in e-cigarette users. In contrast, the cytokines interleukin-4 and interleukin-1β were lower in EC users. “Interleukin-4 tends to be reduced in periodontitis and increases again after treatment,” the researchers explain. “This indicates that species present in the periodontal microbiome are actively suppressing the host’s immune response.” The researchers assume that vaping promotes these very bacteria and thus indirectly contributes to shifting the balance of immune regulators.
Further studies required
“Using e-cigarettes is a relatively new human habit,” says Thomas. “Unlike smoking, which has been extensively studied for decades, we know little about the health consequences of e-cigarette use and are just beginning to understand how the unique microbiome promoted by vaping affects oral health and disease further studies with larger, more comparable groups are needed to understand these associations in more detail.
Source: Scott Thomas (New York University College of Dentistry, USA) et al., mBio, doi: 10.1128/mBio.00075-22