Evidence is building that dental plaque and inflammatory periodontal disease may contribute to the initiation and/or progression of certain lung diseases. Pneumonia is an acute infection of the lung, demonstrating the following respiratory signs and symptoms: cough; shortness of breath; increased respiratory rate; sputum production; and chest pain. Pneumonia may also induce nonspecific systemic symptoms, including fever, fatigue, muscle aches, and lack of appetite. Although pneumonia can be caused by viruses or fungi, bacteria are the most frequent cause of this infection and are the most easily treatable.
Pneumonia often affects individuals with impaired host defense systems, for example, conditions with defects in antibody production, phagocytosis, ciliary function, or reduced CD4+ T-lymphocyte counts, as seen in acquired immunodeficiency syndrome (AIDS) (7). Other underlying respiratory diseases, such as chronic obstructive pulmonary disease, can also lead to pneumonia.
Community-acquired pneumonia is defined as infection occurring in any individual living in the community (7). The annual cost for the treatment of community-acquired pneumonia exceeds $9 billion and affects 4 million adults per year in the USA, c. 20% of whom are admitted to a hospital for treatment. The rate of pneumonia ranges from 8 to 15 per 1000 persons per year, with infants and the elderly having the greatest risk for infection. Rates of pneumonia are higher for men than for women and for black people than for white people. Risk factors for community-acquired pneumonia include alcoholism, asthma, immunosuppression, and age >70 years. Dementia, seizures, congestive heart failure, cerebrovascular disease, tobacco smoking, alcoholism, and chronic obstructive pulmonary disease are risk factors for pneumococcal pneumonia, the most common cause of community-acquired pneumonia.
Evidence is building that an unhygienic oral environment and resulting oral diseases, such as inflammatory gingivitis and periodontitis, can negatively affect systemic health. A straightforward connection between the oral cavity and a specific systemic disease is that between dental plaque, periodontal disease, and lung disease. Accumulating evidence suggests that poor oral health may influence lung function and increase the risk for bacterial lung infection (pneumonia), especially in high-risk patient populations. Three populations for developing pneumonia are the focus of this review: nursing home residents; people hospitalized with acute illness; and those hospitalized who require mechanical ventilation as a result of respiratory failure.
In the past decade there has been an evolution in the classification of pneumonia. Previously, pneumonia was classified as either community acquired or hospital acquired. Hospital-acquired pneumonia was defined as pneumonia occurring with onset >48 hours after admission to hospital. This classification scheme was straightforward and easy to apply. However, in the past decade the classification scheme has evolved, relating to the shift of care for various conditions from the hospital to the outpatient setting for delivery of services such as antibiotic therapy, cancer chemotherapy, wound management, outpatient dialysis centers, and short-term rehabilitation. This shift in care from the hospital to the outpatient, home setting or nursing home gives rise to cases of pneumonia that occur outside the hospital setting, but are clearly related to healthcare environments. Thus, such pneumonia has been referred to as healthcare-associated pneumonia (83).
Nursing-home associated pneumonia is the most important of the common infections affecting nursing home residents because of the high morbidity and mortality associated with this infection (58). Pneumonia is also a common reason for transfer of residents from the nursing home to the hospital (55). Hospital-acquired pneumonia and ventilator-associated pneumonia are amongst the most common infections in the hospital and are together a major cause of morbidity, mortality, extended length of stay and excessive cost in this setting.
This article provides an update on present thinking regarding the pathogenesis, epidemiology, risk factors, microbial etiology, diagnosis, and treatment of nursing home-associated pneumonia, hospital-acquired pneumonia, and ventilator-associated pneumonia. This is followed by a discussion of the role of poor oral health as a risk factor for these diseases. Finally, questions awaiting answers regarding the role of oral health status and pneumonia are posed.