People with insulin resistance are more likely to have severe periodontitis than people without insulin resistance, according a new study. The authors found that insulin resistance can be considered a risk factor for periodontal disease, even for people with a normal weight.
Researchers from South Korea and the U.S. studied the health records of nearly 6,000 South Koreans to see if insulin resistance corresponded to the severity of periodontal disease. They also looked for associations between periodontitis and type 2 diabetes, as well as obesity.
"We hypothesized that insulin resistance aggravates the severity of periodontitis. Moreover, the associations between severe periodontitis and insulin resistance in nonobese adults with normal body mass index (BMI) or waist circumference were evaluated using representative national data," wrote the authors, led by In-Seok Song, DDS, PhD, from the department of oral and maxillofacial surgery at Korea University Anam Hospital (Journal of Clinical Endocrinology & Metabolism, September 6, 2016).
Linking perio disease, weight, and insulin resistance
Insulin resistance occurs when cells don't properly respond to insulin, which is required to digest food. Previous studies have indicated an association between insulin resistance and periodontitis, which the researchers wanted to further explore, while also accounting for body weight.
The international team of researchers used data from the 2008-2010 Korea National Health and Nutrition Examination Survey. In their analysis, they included 5,690 participants, all at least 30 years of age or older, who had moderate to severe periodontal disease, according to the Community Periodontal Index. Nearly 4,500 participants had moderate periodontitis, with pockets of 3.5 to 5.5 mm, while 1,202 had severe periodontitis, with pockets of 5.5 mm or greater.
The researchers also looked at participants' Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) scores, which quantifies a person's insulin resistance by multiplying their fasting insulin levels and fasting glucose levels.
For this study, a man with a HOMA-IR score of 2.21 or higher was considered insulin-resistant, also known as metabolically obese. A woman was considered insulin-resistant if her score was 2.33 or higher. Anyone previously diagnosed with type 2 diabetes also was considered insulin-resistant.
Overall, participants with severe periodontitis had significantly higher insulin-resistance values than those with moderate periodontal disease.
| Insulin-resistance values | |||
| Moderate periodontitis (n = 4,488) | Severe periodontitis (n = 1,202) | p-value | |
| HOMA-IR score | 2.18 | 2.33 | 0.0028 |
After adjusting for weight, insulin-resistant participants with a normal weight also had significantly higher odds of having severe periodontitis than participants with a normal weight who were not insulin-resistant.
The researchers also found people with type 2 diabetes were more likely to have severe periodontitis compared with the groups with normal glucose tolerance and impaired fasting glucose, a type of prediabetes.
"To the best of our knowledge, this is the first report to demonstrate a significant relationship between insulin resistance and severe periodontitis in individuals with normal weight or normal waist circumference," the authors wrote.
Distinguishing between normal BMI and holistic health
Although the study had a large sample size, it consisted entirely of South Korean adults, so its findings may not be able to be generalized to other populations. In addition, because it was a cross-sectional study, a definite causal relationship among insulin resistance, periodontitis, and diabetes can't be made.
Nevertheless, it helped highlight a flaw with some traditional weight measurements, such as BMI or waist circumference. While the tools can be used for wide-scale observations and metrics, they were not designed to be the definitive measure of an individual's health. A person's BMI alone cannot indicate their level of holistic health or disease.
The authors suggested that using metabolic profiles, such as to identify insulin resistance, might provide a better tool for evaluating individual's holistic health and risk for diseases, such as periodontitis.
"This study clearly showed that individuals with insulin resistance were more likely to have severe periodontitis, even among participants with normal waist circumference," the authors concluded. "Obesity might not be directly linked to severe periodontitis, as other studies have shown, and the role of insulin resistance might be a clue."
