People with severe gum disease are at twice the risk of suffering a stroke than those with good oral health, UB researchers have shown in the first national, population-based cohort study of periodontal disease and cerebrovascular disease.

The increased risk was found only for stroke caused by blocked arteries, the most common type of stroke. There was no relationship between oral-health status and stroke caused by hemorrhage inside the brain.

Results of the study appear in the October issue of Archives of Internal Medicine.

"This is the first major study to look at this question," said lead author Tiejian Wu, research assistant professor of social and preventive medicine.

"There have been a few other very limited studies, but the number of subjects was small and drawn from restricted populations. This study also looked at subgroups-men, women, blacks and non-blacks. Periodontal disease was associated with an increased risk for cerebrovascular disease in all groups."

The relationship between gum disease and stroke was even stronger than the apparent link between gum disease and heart disease, he noted.

Recent studies, including several conducted at UB, have found that infection appears to be associated with increases in risk of heart disease, and periodontal disease is one of the most common human infections. However, little is known about the relationship between periodontal disease and cerebrovascular disease.

Wu said periodontal disease is thought to increase the risk of stroke in much the same way it increases the risk of heart attack.

"Bacteria, endotoxins and other bacterial products from gum pockets enter the circulation and may promote an inflammatory response, causing cells to proliferate in the blood vessels and the liver to increase production of clotting factors. Bacteria also may attack the vessel lining and damage endothelial cells," he explained.

"Further, several periodontal pathogens can induce platelet aggregation and may promote plaque formation that can cause blockages and clotting," he said.

The cohort for this study comprised 9,962 adults between the ages of 25 and 75 who took part in the first National Health and Nutrition Examination Survey (NHANES I), conducted from 1972-74, and its follow-up, completed in 1992.

The participants' oral-health status, assessed as part of the NHANES survey, was placed in one of four categories: no periodontal disease, gingivitis, periodontitis or toothless. Gingivitis is an inflammation of the gums and is considered a relatively mild form of periodontal disease. Periodontitis is a severe infection involving the gums, membranes at the base of the teeth and the supporting bone.

Wu and colleagues compiled information on the occurrence of stroke among participants by checking hospital records and death certificates in the follow-up survey. They assessed the risk of cerebrovascular events as a whole and of non-hemorrhagic and hemorrhagic stroke.

Results showed that periodontitis was a significant and independent risk factor for any cerebrovascular event and was associated with a two-fold increase in risk for non-hemorrhagic stroke. The study found no association between periodontal disease and hemorrhagic stroke.

"While more studies are needed for a conclusive statement about the cause-and-effect association, the consistency of the findings in different gender and racial groups, and the strength of the association between two chronic conditions prevalent in the adult population may have important implications for individual and public health," Wu said.

Also participating in this study were Maurizio Trevisan, professor and chair of the Department of Social and Preventive Medicine, and departmental faculty members Christopher Sempos, associate professor; Joan P. Dorn, assistant professor, and Karen L. Falkner, research assistant professor, and Robert J. Genco, professor and chair of the Department of Oral Biology in the School of Dental Medicine.

The study was supported by grants from the National Institutes of Health and by a Buswell Fellowship from the UB medical school.