Researchers have in the past proposed links between oral bacteria and chronic inflammation, particularly in the heart and brain, proposing that bacterial toxins and bacteria themselves enter the bloodstream via damaged gums. This undoubtedly happens, but supporting data is mixed when it comes to the question of whether or not this has a meaningful effect size in comparison to other inflammatory mechanisms and contributions to age-related disease. Here, a different route for bacteria is proposed: passage into the airways and lungs, a possibly explanation as why gum disease and respiratory mortality are correlated in older patients.
The global population is aging, and elderly people have a higher incidence of lower airway diseases owing to decline in swallowing function, airway ciliary motility, and overall immunity associated with aging. Furthermore, lower airway diseases in the elderly tend to have a high mortality rate. Their prevention is important for extending healthy life expectancy and improving the quality of life of each individual.
In recent years, the relationship between chronic periodontitis and oral bacteria, especially the periodontopathic ones, and respiratory diseases (e.g., pneumonia, chronic obstructive pulmonary disease, and influenza) has become clear. In addition, the association of several periodontal pathogens with the onset and aggravation of coronavirus disease 2019 (COVID-19) is also being reported. The oral cavity is the entry point for bacteria and viruses to enter the body, and it is also the entrance to the lower airway, including the bronchi and lungs, in which inflammation occurs during lower airway diseases. Therefore, if aspiration of oral bacteria has an adverse effect on lower airway diseases, it is not difficult to imagine such an effect.
In support of these findings, oral health management has shown to reduce deaths from pneumonia and prevent influenza in nursing homes and inpatient wards. This has led to clinical and multidisciplinary cooperation between physicians and dentists, among others. However, to date, the mechanisms by which chronic periodontitis and oral bacteria contribute to lower airway diseases have not been well understood. Clarifying these mechanisms will lead to a theoretical basis for answering the question, "Why is oral health management effective in preventing lower airway diseases?"