Smoking is linked to a significant reduction in healthy bacteria in the mouth, which could contribute to an increased risk of heart disease and periodontal disease. The impaired oral flora therefore appears to be a significant factor in the negative consequences of smoking.
A recent study involving experts from the University of Michigan examined smoking-related changes in the composition of the oral microbiota and the resulting changes in metabolic pathways, which could be responsible for an increased risk of disease. The results are published in the English-language journal “Scientific Reports”.
Interest in microbiome research is increasing
The so-called microbiome research is a relatively young field and just a few decades ago, the communities of trillions of microorganisms that occur on and in humans (especially in the digestive tract) were considered insignificant for science, the researchers report.
However, it is now known that the so-called microbiome plays an important role in development and health. Intestinal flora in particular is an important area of research today.
Compared to the intestine, the mouth is only sparsely populated with microorganisms, which are also referred to as oral flora. However, this also appears to have far-reaching effects on health.
Saliva samples from more than 1,600 people
In their study, the researchers examined whether changes in the oral flora can be identified in saliva, which serve as biomarkers and can indicate certain diseases, based on saliva samples from more than 1,600 participants.
The participants were divided into different groups based on their smoking status, depending on whether they were currently smoking, had quit smoking or had never started smoking.
Participants who had given up smoking were also asked when they had stopped smoking. Participants who smoked, on the other hand, were asked how many cigarettes they smoked per day.
Altered microbial community in the mouth
The team used universal bacterial identification technology to find out what types of bacteria were present in participants’ mouths and at what frequency.
It was found that people who had never smoked had a significantly different microbial community in their mouths than people who currently smoked or had recently quit smoking, the team reports.
Smoking reduces aerobic bacteria
Smoking cigarettes primarily influenced so-called aerobic bacteria, which are known to need oxygen. The experts found that the number of these bacteria continued to decrease the more cigarettes the participants smoked.
When smoking was stopped, these aerobic bacteria gradually multiplied again. According to the team, the longer people didn’t smoke, the more aerobic bacteria were present in their saliva.
According to the researchers, it takes five years until the number of aerobic bacteria in the oral microbiome of smokers no longer differs from that of people who have never smoked in their lives. This makes it clear that the effects of smoking on the bacteria in the mouth last for years.
Risk of periodontitis and cardiovascular disease?
Since it is known that people who smoke have an increased risk of periodontitis and cardiovascular disease, the researchers say the question arises as to whether the changes in the oral microbiome caused by smoking could play a role in this increased risk.
Some of these bacteria, mainly aerobic bacteria, convert nitrate ingested with food into nitric oxide and if there is too little nitric oxide available, this can lead to poor blood supply to the gums and cardiovascular diseases, the experts explain. Nitric oxide also plays an important role in regulating blood pressure, for example.
The more the participants smoked, the fewer nitrate-reducing bacteria were present in their mouths. This could provide an additional explanation as to why people who smoke have a higher risk of periodontitis and cardiovascular disease.
So far, however, this is just a hypothesis that needs to be tested in further studies, summarizes study author Giacomo Antonello in a press release. (as)