Periodontal Disease and Respiratory Disease: A Systematic

Periodontal disease and respiratory disease: A systematic review of the evidence," Agado & Bowen (2012) perform a systematic review or meta-analysis style of research to determine whether there is a correlation between periodontal disease and pneumonia, or between periodontal disease and chronic obstructive pulmonary disease (COPD), a "common" condition that includes chronic bronchitis and emphysema. Smoking is a major risk factor for COPD; but pneumonia can be caused by a number of different variables, some of which are environmental. It has long been suspected that there is a link between periodontal disease and either pneumonia or COPD, if not both. However, prior research has been inconclusive if these relationships are causal or correlational. A causal relationship has been hypothesized in some research, as the authors cite the fact that "aspiration of oral bacteria has been implicated in the occurrence of healthcare associated pneumonia and exacerbation of COPD," (p. 3). Therefore, dental practices must be aware of risk factors involved for periodontal disease and different types of respiratory disease.

The researchers gathered evidence by searching scholarly databases including Medline, PubMed, and the Cochrane Database of Systematic Reviews. The searches were conducted both electronically and manually. Search terms included "lung disease," "obstructive pneumonia," "periodontal disease," and combinations thereof. However, the authors did not include research on periodontal disease, pneumonia, or COPD that were irrelevant to the current research; the research had to be designed specifically related to the search terms. No practice guidelines, authority opinions, or case studies were included in the meta-analysis of the data. The researchers limited the search to include only journal articles published in English between 1997 and 2011. Moreover, the authors further delimited the data set to include only research conducted on human subjects. However, the authors included in their search a multitude of types of research designs including randomized controlled/clinical trials, systematic reviews/meta-analyses, longitudinal, cohort, and case control studies, multicenter studies, and also epidemiological studies.

Altogether, only 17 articles culled from databases and 4 culled from hand searching were included in the research. The researchers evaluated each of the studies in terms of strength, using parameters such as length of the design, sample size, use of controls, and regression models. Also, strength of evidence was evaluated in terms of a grading system. This grading system, which rates strength of evidence on various criteria, was developed by the Canadian Task Force on Preventive Health Care. Each of two reviewers read the articles to extract evidence related to the research questions and hypotheses.

The results showed that there is no significant correlation between the independent variable (periodontal disease) and the dependent variables (pneumonia or chronic obstructive pulmonary disease). Some of the articles reviewed, including three other systematic reviews/meta-analyses and seven experimental research designs, provided some inconclusive evidence that there may be a connection between periodontal disease and pneumonia. Likewise, five studies that were robust, longitudinal, or matched case control design showed some evidence of a correlation. Likewise, retrospective analyses reveal a conjectural association between the dependent and independent variables. In spite of these connections, it does not appear that there is either a causal or a strong correlational effect. However, meta-analyses / systematic reviews on the subject do indicate there is "fair evidence" supporting a connection between both pneumonia and COPD and periodontal disease. The authors point out that even a fair correlation should inform dental practice, especially with regards to high risk populations. Moreover, the authors note that all three of the diseases in question (periodontal, pneumonia, and COPD) are "complex, multifactorial, and have many risk factors," (p. 7). Some of the potential intervening variables include smoking status, medical history, age, dental caries, missing teeth, dysphagia, and low socio-economic status (p. 7).

Low socio-economic status is something that practitioners should be taking into account when treating patients. The authors point out that, "Canadians living in urban, low socioeconomic areas are 2.7 times more likely to be hospitalized from COPD than those in higher socioeconomic areas," (p. 3). Age and physical condition is also a factor that practitioners need to take into account. This is especially true with regards to aspiration pneumonia, which can be caused "when food or liquids from the mouth, gastric contents, or oropharyngeal secretions are inadvertently inhaled into the lower respiratory tract," (p. 3). The elderly or infirm dependent on external feeding mechanisms or who are missing teeth might be particularly susceptible. The authors note that elderly living in long-term care facilities are also to be classified as a high-risk community. In fact, there are several identifiable mechanisms by which oral bacteria can precipitate or cause a respiratory infection. High risk communities, including the elderly and people who smoke, should be examined more closely by dentists due to the potentially debilitating if not fatal impact of developing a respiratory illness. Even if there is no direct causal relationship, the literature does support a general concern for these risk factors.

Inadequate oral hygiene is another potential precipitating factor. Although no direct causal relationship can be revealed, poor oral remains a major risk factor for at least periodontal disease. The presence of oral bacteria due to poor oral hygiene is likely to exacerbate pre-existing tendencies to develop respiratory infections. Therefore, it is important to promote oral hygiene in general to prevent the build up of bacteria that could lead to or exacerbate an existing respiratory condition.