Scientists find link between mouth bacteria to head and neck cancers

Bacteria that thrive in people’s mouths could increase the risk of head and neck cancers, new research shows.

Head and neck squamous cell carcinoma (HNSCC), which develop in the mouth, nose, and throat, are among the most common forms of the disease in Europe with more than 150,000 people diagnosed every year.

These cancers are more likely to affect men and kill more than half of patients within five years.

The new study, conducted by researchers at New York University (NYU) and published in the journal JAMA Oncology, found that 13 of the hundreds of bacteria species in people’s mouths are linked to a 30 per cent higher likelihood of developing HNSCC.

“These bacteria may serve as biomarkers for experts to flag those at high risk,” Soyoung Kwak, a postdoctoral researcher at NYU’s medical school, said in a statement.

The study compared 236 people with HNSCC to 458 people without it.

The cancer patients tended to have higher rates of tobacco and alcohol use, as well as a higher rate of a particularly dangerous strain of oral human papillomavirus (HPV) – all of which are risk factors for HNSCC.

However, even after researchers adjusted for other issues, the 13 bacteria still turned up as risk factors. The species tended to be the same regardless of where the person had cancer, for example in the oral cavity, pharynx, or larynx.

Warning to practice good oral hygiene

Previous bacterial sequencing and smaller studies suggested there could be a link between oral health and HNSCC, but the new analysis is the first to identify the problematic bacteria.

The study looked at correlation between the bacteria and cancer, so it doesn’t establish that bacteria directly causes the diseases.

“As the results are based on just over 200 cancer cases, more research in larger populations is needed to explore the link between oral hygiene and head and neck cancer,” Dr Claire Knight, Cancer Research UK’s senior health information manager, told Euronews Health. She was not involved with the study.

Even so, the researchers said the link appears strong enough to serve as a reminder to practise good oral hygiene.

“Brushing your teeth and flossing may not only help prevent periodontal disease, but also may protect against head and neck cancer,” Dr Richard Hayes, a study co-author and professor at NYU’s medical school, said in a statement.

Researchers said the next step is to identify how exactly these bacteria contribute to cancer risks – and how they can be stopped.

Meanwhile, Knight said that people worried about head and neck cancers should drink less alcohol and stop smoking, given those are two major risk factors.

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“Cutting down on alcohol intake and finding support to stop smoking are changes you can make to help reduce your risk of developing the disease,” Knight said.