Public Health Implications of Chronic Periodontal Infections in Adults

Periodontitis and Cardiovascular Diseases—Comorbid Conditions?
Philippe Hujoel, LTH, MSD, MS, PhD, Professor, Department of Dental Public Health Services, University of Washington School of Dentistry, Seattle, Washington

Apparently well-controlled epidemiological analyses of data from the First National Health and Nutrition Examination Survey (NHANES I) demonstrate that coronary heart disease increases the risk for incident lung cancer by 60% (p < 0.05). Does this mean that coronary heart disease causes lung cancer? Probably not. Lung cancer and coronary heart disease are comorbid conditions - conditions or diseases that co-exist because of common causal factors. By definition, associations between comorbid conditions are to be expected.

Are conditions between periodontitis and these systemic diseases a reflection of comorbidity? Periodontitis, lung cancer, chronic obstructive pulmonary disease, cardiovascular disease, diabetes, and low birth weight are additional examples of comorbid conditions—diseases or conditions that co-exist because of a common causal factor—smoking.

Five lines of evidence indicate that smoking is the primary contributor of the purported associations between periodontitis and systemic diseases. First, no periodontitis-systemic disease associations have been identified among people who have never smoked. Second, periodontitis and smoking mimic one another almost perfectly with respect to the types of diseases they are associated with. Third, only studies with inadequate adjustment for smoking report significant periodontitis-systemic disease associations. Fourth, eliminating dental infection, unlike smoking cessation, does not reduce a person's risk for coronary heart disease or C-reactive protein levels. Fifth, in NHANES III, probing attachment levels predict serum cotinine levels, even when taking into consideration self-reported cigarette use. Unless it can be shown that plaque secretes nicotine, or that attachment loss causes alterations in nicotine absorption or metabolism, the NHANES III findings are the strongest direct evidence that adjustment for self-reported smoking characteristics is insufficient to eliminate spurious associations between periodontitis and systemic diseases.

How can causal associations between comorbid conditions be investigated? In the journal Nature, a review article on epidemiology in the 21st century indicated that the impact of smoking on early morbidity and mortality is so large that progress in understanding the more subtle disease etiologies can only be made when analyses are restricted to people who have never smoked. For instance, it is now generally accepted that reliable evidence regarding the impact of obesity on cancer can only be obtained when the analyses are limited to people who have never smoked (never-smokers). These lessons learned in medical epidemiology apply to dental epidemiology. A logical start for an earnest investigation into the association between periodontitis and cardiovascular diseases is a reanalysis of existing data among never-smokers. While each separate study is likely to be underpowered, a synthesis of available studies can provide guidance about the direction, if any, that periodontitis-systemic disease research needs to take to progress. Such a synthesis will provide reliable evidence regarding the veracity of the associations between periodontitis and cardiovascular disease, and identify which periodontitis-systemic disease associations are worthy of further investigation.

What’s next? Until file drawers are opened and available data for people who never smoked is synthesized, the public health implications of the current research findings are clear: smoking destroys both oral health and systemic health. Dental professionals should continue to play an important role in counseling patients on the hazards of smoking and oral diseases.

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Historical Document
Page last reviewed: February 2, 2005
Content source: Division of Oral Health, National Center for Chronic Disease Prevention and Health Promotion