A new study suggests that regularly brushing and flossing your teeth could reduce your risk of head and neck cancer. Neglecting oral hygiene can not only increase the risk of diabetes and high blood pressure, but also head and neck cancers, according to the study by US scientists.  

Led by researchers at NYU Langone Health and its Perlmutter Cancer Center, the new study found that more than a dozen bacterial species among the hundreds that live in people's mouths have been linked to a collective 50 per cent increased chance of developing head and neck squamous cell carcinoma (HNSCC). While small studies have tied some bacteria in these regions (the oral microbiome) to the cancers, the exact bacterial types most involved have remained unclear until now.

The findings

The study, published in the journal JAMA Oncology, looked at the genetic makeup of oral microbes collected from healthy men and women. Of the hundreds of different bacteria routinely found in the mouth, 13 species were shown to either raise or lower the risk of HNSCC. Overall, this group was linked to a 30 per cent greater likelihood of developing the cancers. In combination with five other species often seen in gum disease, the overall risk was increased by 50 per cent.

"Our findings offer new insight into the relationship between the oral microbiome and head and neck cancers," said study lead author Soyoung Kwak, PhD. "These bacteria may serve as biomarkers for experts to flag those at high risk," added Kwak, a postdoctoral fellow in the Department of Population Health at NYU Grossman School of Medicine.

Previous investigations had uncovered certain bacteria in tumor samples of people already diagnosed with these cancers, says Kwak. Then, in a small 2018 assessment, the current research team explored how microbes in healthy participants may, over time, contribute to future risk of HNSCC.

Study underscores importance of good oral hygiene

Their latest study is the largest and most detailed analysis of its kind to date, says Kwak. It is also among the first to examine whether common fungi, organisms like yeast and mould that, along with bacteria, make up the oral microbiome, might play a role in HNSCC. The new experiments found no such role for fungal organisms.

"Our results offer yet another reason to keep up good oral hygiene habits," said study co-senior author Richard Hayes, DDS, MPH, PhD. "Brushing your teeth and flossing may not only help prevent periodontal disease, but also may protect against head and neck cancer," added Hayes, a professor in the Department of Population Health at NYU Grossman School of Medicine and a member of its Perlmutter Cancer Center.

The researchers emphasised that their study was designed to identify correlations between risk of cancer and certain bacteria in the mouth, but not to establish a direct cause-and-effect link. That will require further research.

"Now that we have identified key bacteria that may contribute to this disease, we next plan to explore the mechanisms that allow them to do so and in what ways we can best intervene," said study co-senior author Jiyoung Ahn, PhD. Ahn is a professor in the Departments of Population Health and Medicine at NYU Grossman School of Medicine and is the associate director for population research at its Perlmutter Cancer Center. Ahn cautions that while the added risks from bacteria are concerning, overall cases of head and neck cancer remain fairly uncommon.

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