Researchers from the School of Dental Medicine at the University at Buffalo have found that obesity is significantly related to periodontal disease through the pathway of insulin resistance.

Using data from the Third National Health and Nutrition Examination (NHANES III), researchers have shown that overweight people with the highest levels of insulin resistance were 50 percent more likely to have severe periodontal disease, compared to overweight people with low insulin resistance.

"This study suggests yet another way bacteria in the mouth are substantial sources of systemic challenge," says Sara Grossi, UB clinical assistant professor of oral biology, director of the UB Periodontal Disease Research Center and lead author of the study. "The mechanism that increases insulin resistance is possibly another pathway that explains how bacteria from periodontal disease affects the risk Type 2 diabetes and heart disease. They are all different parts of the puzzle."

Obesity is increasing at alarming rates among American adults, juveniles and children. Recent research had hinted at a possible relationship between periodontal disease and obesity, Dr. Grossi notes, but no systematic studies have been published. To investigate this question more fully, Dr. Grossi and colleagues at the Periodontal Disease Research Center analyzed data on periodontal status, body mass index (BMI), fasting insulin and fasting glucose from 10,836 participants who took part in NHANES III.

Persons with diabetes and those having fewer than six teeth were excluded. Persons with a BMI of more than 27 were considered overweight. BMI is an index that represents the ratio of a person's weight to height. It is determined by dividing the weight in kilograms by the height in meters squared. Periodontal disease was assessed as having an average loss of gum attachment from teeth of more than 1.5mm.

An index of insulin resistance -- a condition in which the body does not respond well to the action of insulin -- was determined by multiplying the amount of fasting insulin by the amount of fasting glucose.

Dr. Grossi's analysis found that overweight people with an insulin-resistance index in the top quartile were nearly 50 percent more likely to have severe periodontal disease, compared to those with a high BMI and low insulin resistance.

"Acute infections cause metabolic disturbances and periodontal disease is one of humankind's most common chronic infections," Dr. Grossi says. "In this case, we think bacteria from gum disease may interfere with fat metabolism, leading to elevated LDL cholesterol and total cholesterol. This has been shown in small case-control studies and animal studies.

"Now we see a relationship between obesity, insulin resistance and periodontal disease in a large, population-based cohort,” says Dr. Grossi. “This relationship is significant because obesity is an important risk factor for Type 2 diabetes and heart disease. It is possible that periodontal disease contributes to increased morbidity in overweight or obese individuals. Physicians once thought that the damage from periodontal infection was limited to the teeth and gums. We now know that oral health must be watched much more closely."

Dr. Grossi says molecular biology studies are needed to unravel the actual mechanism and biological basis of the obesity-periodontal disease relationship.

Alex Ho, statistician in the UB Department of Oral Biology, also contributed to the study. The research was funded by a grant from the U.S. Public Health Service.

Edited by Chris Smith