Lungs

Synopsis

Information

Periodontitis has been positively associated with many non-communicable conditions such as cardiovascular disease and diabetes. The relationship between periodontitis and respiratory illness has been less exploredⁱ.

Studies of epidemiology, microbiology and molecular biology have determined a link between the oral microbiome and respiratory diseases. Bacteria from the oral cavity is known to foster the population of the lung microbiome. There is growing evidence that microbial misbalance in the oral cavity contributes to respiratory diseasesⁱ,ⁱⁱ.

Both periodontitis and respiratory illness are common diseases with COPD amongst the top 10 diseases inducing long term disability. In 2016, 251 million people were diagnosed with COPD with this number expected to grow. In 2020, COPD was the fifth underlying cause of death in Australiaⁱⁱⁱ. Periodontitis affects 45-50% of the global adult populationⁱⁱ.

The evidence for mechanisms underlying the relationship between periodontitis and respiratory diseases is early due to confounded effects from factors such as tobacco and comorbid illnesses. Furthermore, the relationship being uni or bi-directional has yet to be determined with factors such as medicaments shown to decrease saliva flow and thus lead to oral microbial imbalance that then affects lungs. Despite these limitations, there are some studies suggesting biological plausibility for the associationⁱ,ⁱⁱ,^iv.

Several hypotheses have been proposed to explain the link between periodontitis and respiratory illness.

• 1. Aspiration of oral bacteria exacerbating inflammation in the lungs and vascular cell dysfunction
• 2. Indirect low-grade inflammation generated by periodontitis can lead to cytokines impacting pulmonary epithelium

Studies assessing the association between COPD, OSA, COVID-19 and periodontitis have determined statistical significance, but the evidence base is still earlyⁱⁱ. Specific to COVID-19, studies have determined that the oral epithelium is highly susceptible to viral infection and contains the ACE2 receptor for SARS-CoV-2. Saliva contains 108 copies per mL of SARS-CoV-2. High salivary viral load has been considered to be a poor outcome for death^v.

The association between oral bacteria and aspiration pneumonia is emerging. Aspiration pneumonia develops prevalently in patients with oral dysphagia, the impaired swallowing misdirects regurgitated gastric contents or oropharyngeal secretions to the lungs. Studies have found oral pathogens in aspiration pneumonia cultures suggesting that increased levels of pathogenic bacteria in the mouth will increase the risk of transfer in susceptible individuals to the respiratory tract and cause aspiration pneumonia.^vi, ^vii

There is sufficient evidence to indicate that maintenance of oral hygiene will reduce the impact on aspiration of oral pathogens to respiratory tissue. Evidence is too early to suggest any causal link between the oral cavity and respiratory diseases, but the importance of regular oral care, particularly in susceptible individuals will reduce the burden of inflammatory disease.