Relationship Between Metabolic Syndrome and Periodontal Diseases According to Socio-Demograpic Variables

Article information

Exerc Sci. 2025;34(2):117-125

Publication date (electronic) : 2025 May 30

doi : https://doi.org/10.15857/ksep.2025.00101

Ah-Reum Shin, PhD ¹^,^†

, Yi Sub Kwak, PhD ²^,^†

, Hye-Young Kim, PhD ³^,

¹Doctoral Program in Public Health, Department of Public Health, Graduate School, Sahmyook University, Seoul, Korea

²DEU Exe-Physio Lab, Department of Physical Education, Dong Eui University, Busan, Korea

³Deparrtment of Dental Hygiene, Kangwon National University, Samcheok, Korea

Corresponding author: Hye-Young Kim Tel +82-10-4068-2400 Fax +82-505-182-6915 E-mail khy0606@daum.net

†These authors contributed equally.

*This paper was supported in part by research funds from Kangwon National University.

Received 2025 February 26; Revised 2025 April 2; Accepted 2025 April 17.

Abstract

PURPOSE

Due to the changes in the Westernized diet and lifestyle, the number of metabolic syndrome and periodontal disease cases in Korean adults is on the rise. Since recently, however, considering the increasing social awareness of the importance of health Korean adults and the necessity of establishing policies for oral health promotion, it has become important to establish basic data on the formulation of a national oral health promotion policy by identifying the relationships among metabolic syndrome, social factors, and periodontal disease.

METHODS

The obtained data were analyzed using the data of the 6th National Health and Nutrition Survey (2015), which are representative of the national population, and of those who are over 19 years old who have completed the metabolic syndrome survey and oral examination. The statistical analysis of the data was performed using the SPSS (PASW statistics) 22.0 statistical program and chi square test and binomial logistic analyses.

RESULTS

The main results of the study are as follows. First, for the metabolic syndrome judgment factors, the prevalence of periodontal disease was higher in the order of the metabolic syndrome group, metabolic syndrome risk group, and normal group. The metabolic syndrome factors showed that the distribution of the periodontal disease prevalence rate was different. Second, the results of the analysis of the effect of periodontal disease through binomial logistic regression analysis showed that in the normal group, metabolic syndrome risk group, and metabolic syndrome group, sex, age, and income level exerted an influence on periodontal disease, and such influence was statistically significant.

CONCLUSIONS

In conclusion, the results of this study can be used as basic data for the formulation of a comprehensive policy for the development of programs for the prevention of metabolic syndrome and periodontal disease and the reduction of the social problems caused by chronic diseases

Keywords: Metabolic syndrome; Periodontal disease; Social factors; Korean adults

INTRODUCTION

Due to the high level of medical development and the improved stan-dard of living in the modern society, the average life expectancy has been prolonged, and the society is aging. Based on Statistics Korea data, the geriatric population in South Korea will increase from 14.3% in 2018 to 20.8% in 2026 [1]. Aging can cause weakness of all the body functions as well as declining oral health, and there is increasing research interest in oral health among the elderly people [2]. In particular, periodontal disease, a representative oral disease, can cause loss of teeth and complex health problems if not treated in a timely manner [3]. The prevalence rate of periodontal disease in the Korean adults has increased since 2013 [4] and was so far highest in 2016 [5], and it has been reported that one in three adults currently has periodontal disease [6]. Based on these facts, periodontal disease should be recognized as a very important disease as its financial burden for both individuals and the nation is high.

It has been known that periodontal disease is closely related to metabolic syndrome [7], and it has been shown that periodontal disease greatly affects fasting blood glucose, triglyceride, HDL cholesterol, hypertension, and abdominal obesity [8]. It has been reported that high fasting blood glucose can act as a risk factor causing periodontal disease [9], and there is a significant correlation between dyslipidemia and periodontal disease [10]. In a study on the association between periodontal disease and health status in adults aged between 23 and 83, the association between low HDL cholesterol and periodontal disease was reported [11], and it was confirmed that the hypertension patients had a higher prevalence of periodontal disease [12]. In addition, for the abdominal obesity factor, the overweight or obese adults had a higher risk of developing periodontal disease compared to the adults with a normal BMI, and the periodontal disease prevalence was higher in the adults with a larger waistline [13]. The periodontal disease risk was about 20% higher in the subjects with a higher BMI and three or more metabolic syndrome factors [14]. For the criteria of metabolic syndrome diagnosis, the subjects with metabolic syndrome had a higher risk of periodontal disease than the normal group [15], and significantly higher effects were shown on periodontal disease. It was found that periodontal disease is a complex and progressive chronic inflammatory condition that leads to the loss of alveolar bone and teeth. And moreover, it causes chronic inflammation and various systemic diseases such as obesity, diabetes mel-litus, dyslipidemia, insulin resistance, hypertension and interconnected systemic diseases. Many studies on metabolic syndrome and periodontal disease have been continuously reported, and the prevalence rates of metabolic syndrome and periodontal disease have increased nationally as well as globally. Thus, studies on related chronic diseases as a social problem have been on the rise [16], and individual as well as national management is necessary. In addition, periodontal disease is known to affect the sociodemographic factors in various ways. Based on a study on periodontal health status in Danes, it was 7.7% in the Danes aged 35-44 and 2.4% in the Danes aged 65-74, showing that the teeth preservation condition becomes poor as the age increases [17], and the teeth health condition becomes better as the education level increases. Furthermore, chronic periodontal disease was found to have a higher prevalence among people with a low education level, and also showed a very close relationship with smoking [18]. As such, oral health status has a large impact on social factors.

Although many studies have been conducted globally on the effects of metabolic syndrome and sociodemographic factors on periodontal disease, there have been very few studies on such on a nationally representative large population in South Korea, and also few studies on periodontal disease with the sociodemographic variables. Therefore, this study used the data from the 6th Korea National Health and Nutrition Examination Survey (2015), a representative study with confirmed reli-ability, to analyze the effects of metabolic syndrome in Korean adults and sociodemographic factors on periodontal disease, and to investigate their associations should not be overlooked.

METHODS

1. Subject selection

The subjects of this study were 5,945 male and female adults aged 19 or older who received health examination, oral examination and periodontal disease examination. They were categorized into three age groups: young adults (aged 19-29), middle-aged adults (aged 30-64), and elderly adults (aged 65 or older).

2. Measurement procedure

The sociodemographic characteristic variables included sex, age, income, marital status, and education level, and the metabolic syndrome factors included high blood glucose, hypertriglyceridemia, low HDL cholesterol, hypertension, and obesity. National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III) [19] was used for the metabolic syndrome diagnostic criteria (Table 1).

Table 1.

NCEP ATP III diagnostic criteria

For the analysis method of metabolic syndrome, the clinical guideline of 2001 NCEP ATP III, which newly defined metabolic syndrome, was used. Any three of the following five diagnostic criteria led to metabolic syndrome diagnosis: fasting glucose 110 gm/dL or more, serum triglyceride 150 mg/dL or more, serum low HDL cholesterol less than 40 mg/dL, taking antihypertensive drugs or diastolic pressure 130 mmHg or more or systolic pressure 85 mmHg or more, and BMI 25 kg/m² or more [20]. The examination methods, equipment, and reagents that were used for each metabolic syndrome factor are as follows.

The fasting blood glucose level was determined through the hexoki-nase UV method, and Hitachi Automatic Analyzer 7600-210 (Hitachi, Japan) was used as the equipment while Pureauto S GLU (Sekisui, Japan) was used as the reagent. The enzymatic method was used to test for hypertriglyceridemia, with Hitachi Automatic Analyzer 7600-210 (Hitachi, Japan) used as the equipment and Pureauto S TG-N (Sekisui, Japan) as the reagent. The HDL cholesterol was tested using the homogeneous enzymatic colorimetric method, with Hitachi Automatic Analyzer 7600-210 (Hitachi, Japan) as the equipment and Cholesteset N HDL (Sekisui, Japan) as the reagent. The hypertension diastolic and systolic pressure quality management and pulse rate measurement was further strength-ened, and the blood pressure measuring staff certification method was introduced while of blood pressure measurement and measuring envi-ronment standardization was continuously conducted. The BMI was calculated using the weight (kg), and the height² (m²) was used for the obesity index. Probe was used to detect the periodontal disease degree (Dental Studio, German).

3. Data collection and analysis

This study was conducted using the data from the 6th Korea National Health and Nutrition Examination Survey (KNHANES) (2015). KNHANES is conducted based on Article 16 of the National Health Promotion Act proclaimed in 1995, and is composed of a health behavior survey, a health interview survey, a chronic disease condition survey, an oral examination, and a nutrition survey. KNHANES is a combined form of Korea National Health Survey and Korea National Nutrition Survey and provides reliable government-accredited statistics based on Article 17 of the Statistics Act. It is a nationally representative health and nutrition surveillance study. This study selected sociodemographic characteristics, factors consisting metabolic syndrome and their diagnostic criteria, and periodontal disease variables from KNHANES and used these according to the study purposes. The detailed analytic methods are as follows.

First, frequency analysis was conducted to investigate the sociodemoraphic factors and the characteristics of the metabolic syndrome factors, and their criteria and descriptive statistics were used. Second, chi square test analysis was conducted to investigate periodontal diseases based on the subjects’ characteristics, where the differences among the sociodemographic characteristics, the metabolic syndrome factors, and their diagnostic criteria were tested. Third, binomial logistic regression analysis was conducted to investigate the effects of the subjects’ metabolic syndrome on periodontal disease. The results were presented using the odds ratio.

Statistical analysis was conducted in this study using SPSS 22 (IBM SPSS Statistics 22.0, Chicago, IL, USA).

RESULTS

1. Periodontal disease prevalence rates by sociodemographic characteristic

The prevalence rates of periodontal disease by sociodemographic characteristic are shown in Table 2. The prevalence rate of periodontal disease was found to be 38.8% (832) in 2,090 men and 29.5% (809) in 2,746 women, and it was shown that the prevalence rate is higher in men than in women. Thus, the periodontal disease prevalence rate by sex showed a difference in distribution. By age, the periodontal disease prevalence rate was shown to increase along with the age. Young adults (aged 19-29) showed the lowest prevalence rate among all the age groups (10.8% or 139 cases in 1,292 young adults). Out of 1,888 middle-aged adults (aged 30-64), 721 (38.2%) had periodontal disease, showing a relatively big increase compared to the young adults. Out of 1,656 elderly adults (aged 65 or older), 781 (47.2%) had periodontal disease, showing a similar prevalence rate as the middle-aged adults. The periodontal disease prevalence rates by age thus showed a difference in distribution. As for the income level, among the 1,134 subjects whose income was less than KRW1,500,000, 525 (46.3%) had periodontal disease, the highest prevalence rate among all the income level groups. Among the 2,005 subjects whose income was between KRW1,500,000 and KRW4,500,000, 673 (33.6%) had periodontal disease, while the 1,668 subjects whose income was more than KRW4,500,000 had the lowest prevalence rate (25.7%, 429 subjects). Therefore, the periodontal disease prevalence rate increased as the income decreased. The periodontal disease prevalence rates by income level showed a difference in distribution. As for the marital status, 336 (47.5%) of the 707 single adults had a higher periodontal disease prevalence rate than the married adults (1,223/3,342; 36.6%). The prevalence rate by marital status thus showed a difference in distribution. For the education level, 463 (47.1%) of the 984 elementary school graduates or lower, 239 (48.3%) of the 495 middle school graduates, 456 (30.3%) of the 1,504 high school graduates, and 341 (22.9%) of the 1,489 college graduates or higher had periodontal disease, showing that the lower the education level is, the higher the periodontal disease prevalence rate. The prevalence rate by education level thus showed a difference in distribution.

Table 2.

The incidence of periodontal disease according to sociodemographic variable Unit: person (%)

2. Periodontal disease prevalence rate by metabolic syndrome factor

The periodontal disease prevalence rates by metabolic syndrome factor are shown in Table 3. The highest prevalence rate was shown in the subjects with hypertension, followed by those with high fasting blood glucose, hypertriglyceridemia, abdominal obesity, and low HDL cholesterol, in descending order. Of the 710 subjects with hypertension, the 1,631 subjects with high fasting blood glucose, the 1,326 subjects with hypertriglyceridemia, the 1,698 subjects with obesity, and the 2,002 subjects with low HDL cholesterol, 343 (48.3%), 719 (44.1%), 562 (42.4%), 690 (40.6%), and 772 (38.6%), respectively, had periodontal disease. The periodontal disease prevalence rates by metabolic syndrome factor thus showed a difference in distribution.

Table 3.

The incidence of periodontal disease according to metabolic syndrome factor Unit: person (%)

3. Periodontal disease prevalence rates by metabolic syndrome diagnostic criterion

The periodontal disease prevalence rates by metabolic syndrome diagnostic criterion are shown in Table 4. The periodontal disease prevalence rates by metabolic syndrome (n=4,836) diagnostic criterion are shown in the order of the metabolic syndrome group, the metabolic syndrome risk group, and the normal group. Of the 1,159 subjects in the metabolic syndrome group, 537 (46.3%) had periodontal disease, and of the 2,374 subjects in the metabolic syndrome risk group and the 1,303 subjects in the normal group, 853 (35.9%) and 251 (19.3%), respectively, had the same disease. The periodontal disease prevalence rates by metabolic syndrome thus showed a difference in distribution.

Table 4.

Periodontal disease prevalence rates by metabolic syndrome diagnostic criterion Unit: person (%)

4. Effects of metabolic syndrome on periodontal disease

Binomial logistic regression was used to investigate the effects of metabolic syndrome on periodontal disease when adjusted for sociodemographic variables, and the results are presented in Table 5.

Table 5.

Effects of metabolic syndrome on periodontal disease

The regression models of the effects of metabolic syndrome on periodontal disease were significant (χ² =304.726, p <.001). Model I included the sociodemographic characteristics as covariates, and model II additionally included the metabolic syndrome diagnostic criteria (normal group, metabolic syndrome risk group, and metabolic syndrome group) in the sociodemographic characteristics. As a result, model II examined the effects of the metabolic syndrome diagnostic criteria variable and showed that the criteria (normal group, metabolic syndrome risk group, and metabolic syndrome group) had effects on periodontal disease.

The metabolic syndrome diagnostic criteria variables in model II showed that the metabolic syndrome risk group had a 1.402 higher risk of developing periodontal disease than the normal group (OR=1.402, p <.001) while the metabolic syndrome group had a 1.837 higher risk than the normal group (OR=1.837, p <.001). The higher risks of developing periodontal disease in the metabolic syndrome risk group and metabolic syndrome group than in the normal group indicated that the risk of developing periodontal disease increased as the metabolic syndrome factors increased, and showed that the metabolic syndrome factors af-fected periodontal disease.

DISCUSSION

Periodontal disease is the most common oral disease in the Korean adults. While the cases of dental caries are decreasing, the cases of periodontal disease have been increasing [21]. In the modern society, what needs as much attention as periodontal disease is metabolic syndrome, which accompanies diseases related to five consisting factors (glucose, lipid, HDL-C, hypertension, and obesity). The prevalence rate of metabolic syndrome based on the NCEP-ATP III definition is about 19.8-30.9% worldwide, and the prevalence rate increases along with the age [22]. The metabolic syndrome prevalence rate in the U.S. increased from 23.7% in 1998-1994 [23] to 34.3% in 2003-2006 based on the National Health Examination and Nutrition Survey data [24]. Compared to the normal group, the group with three or more metabolic syndrome factors had a higher risk of developing periodontal disease, and the group with four to five metabolic syndrome factors had a higher paradental pocket depth to clinical bonding loss risk ratio [25], consistent with the data from this study. From the analysis of the sociodemographic variables, it was found that there is a higher periodontal disease prevalence rate in men than in women. It was considered that this result could be attribut-able to the higher smoking rate among men than among women. The periodontal disease condition was worse in the older subjects due to the weakness of their skeletal system and periodontal bone caused by their reduced physical strength and accelerated aging. In the precedent studies, age was shown to be very much associated with periodontal disease among the metabolic syndrome factors [26,27], with the periodontal disease prevalence rate being 2.3% in the 24- to 39-year-old subjects and 11.6% in the 40- to 59-year-old subjects, showing that the prevalence rate increased along with the age [28]. Furthermore, a study on the periodontal disease prevalence rate among Germans reported that the periodontal disease prevalence rate increased along with the age, and plateaued after reaching 50-59 years old [29]. Therefore, it can be said that age increase has a bad effect on periodontal disease.

For the periodontal disease prevalence rates by marital status, there was a higher prevalence rate in the married subjects than in the single subjects. As for the periodontal disease prevalence rates by income and education level, the subjects with lower income and education levels were shown to be more likely to have periodontal disease and poor oral health conditions. In a study on chronic periodontal disease in Jews living in Je-rusalem aged 34-44, there was a higher prevalence rate in the subjects with a lower income [30], and in a study on the periodontal disease prevalence rate in Indian adults aged 35 or older, a significantly higher prevalence rate was shown in the subjects with a low education level than in those with a high education level [31]. As such, it was shown that the periodontal disease prevalence rate is closely associated with age, sex, marital status, and income and education level [32], and this is consistent with the results of this study. Therefore, utilizing a sociodemographic index that can be evaluated orally or through a survey questionnaire during the examination of the adult oral health status can have a strategic significance.

It is known that the periodontal disease prevalence rate increases along with the metabolic syndrome risk or the number of metabolic syndrome factors, and that five metabolic syndrome factors have complex interactional effects on periodontal health and are closely related to periodontal disease. In addition to periodontal disease, it is known that metabolic syndrome increases the risk of developing cardiovascular disease [33] and type 2 diabetes [34] and can cause other chronic diseases [35,36]. It is also known that periodontal disease and loss of teeth are complications of diabetes and insulin resistance [37], and that periodontitis can aggravate the blood glucose level, which can cause diabetes [38]. Therefore, periodontal disease causes diabetes and aggravates the blood glucose level. Furthermore, hypertriglyceridemia can result in the aggra-vation of periodontal disease, and high blood glucose interrupts the inflammation response through the deposition of a glycosylated product in the tissue, including the periodontal tissue, and the stimulation of inflammatory cytokine [39]. Based on this mechanism, periodontal patho-genic bacterial infection can damage the periodontal tissue, and the inflammation-induced cytokine and hormones produced in abundance by hypertriglyceridemia can increase periodontal infection. Furthermore, the accumulation of cholesterol and lipid in the atrial wall or im-mune cells causes an inflammatory response due to the decreased HDL-C level, which eliminates the lipid on the arterial walls. Therefore, inflammatory cytokine potentially contributes to insulin resistance and causes periodontal disease [39,40]. In addition, it was reported that the obesity index could be utilized as an index predicting the progress of periodontal disease [41,42]. As such, the metabolic syndrome factors (blood glucose, triglyceride, HDL-C, blood pressure, and obesity) affect periodontal disease both directly and indirectly. When the number of metabolic syndrome factors increases, the effects on the periodontal disease risk likewise increase. Also, adult chronic diseases cause periodontal tissue inflammation and can lead to disease.

The cases of metabolic syndrome have increased worldwide. Preventing metabolic syndrome and reducing the cases of periodontal disease by managing the risk factors of metabolic syndrome, such as lack of exercise, irregular eating habits, smoking, drinking, and stress, are urgent tasks as well as oral hygiene management. This study is significant as it reported the association between metabolic syndrome and periodontal disease using the nationally representative and reliable data from KNHANES. Spe-cific methods and strategies should be researched for managing metabolic diseases that can regulate oral hygiene and chronic inflammation in the near future.

CONCLUSION

In this study, the periodontal disease prevalence rate in Korean adults was shown to be closely related to the sociodemographic factors. That is, it was shown that sex, age, marital status, and income and education level have direct effects on the periodontal disease prevalence rate. Among these, sex and age were shown to influence the periodontal disease prevalence rate the most, followed by education level, income level, and marital status, in descending order. This means that the sociodemographic variables are very important in the development of periodontal disease, and these factors should thus not be overlooked.

The periodontal disease prevalence rates by metabolic syndrome diagnostic criterion were highest in the metabolic syndrome group, followed by the metabolic syndrome risk group and the normal group, in descending order. It was shown that as the number of metabolic syndrome factors increased, the periodontal disease prevalence rate also increased. Although there were some differences in periodontal disease prevalence rate among the metabolic syndrome factors, all the factors showed effects on the periodontal disease prevalence rate. In particular, the initial development of periodontal disease can be predicted by metabolic syndrome using the human blood index (blood glucose, triglyceride, and HDL-C), blood pressure, and obesity index, which showed the importance of management and prevention.

Overall, it is recommended that the Korean oral health program be made to focus on periodontal disease prevention and promoting appro-priate oral health management in daily life using continuous education media. Furthermore, systematic oral health education should be given to metabolic syndrome patients with periodontal disease, and a joint oral health policy project and joint program development between the gov-ernment and the community are urgently needed, along with individual oral health management. In addition, cohort analysis must be conducted on the whole nation using big data to identify the causal relationship between metabolic syndrome and periodontal disease, by applying a spe-cific index of oral health, which will lead to finding scientific treatment methods for the patients.

Notes

CONFLICT OF INTEREST

The authors declare that they have no conflicts of interest related to this study.

AUTHOR CONTRIBUTIONS

Conceptualization: AR Shin, YS Kwak, HY Kim; Data curation: AR Shin, HY Kim; Formal analysis: AR Shin, YS Kwak, HY Kim; Method-ology: AR Shin, YS Kwak, HY Kim; Visualization: AR Shin, YS Kwak; Writing - original draft: AR Shin, YS Kwak, HY Kim; Writing - review & editing: YS Kwak, HY Kim.

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Classification	Diagnostic criteria	Definition
High blood glucose	Blood sugar disorder: Fasting glucose levels of at least 100 mg/dL or history of diabetes or diabetes medication
Hypertriglyceridemia	Triglyceride: 150 mg/dL or greater	1. Normal group: non-applicable
Low HDL cholesterol	HDL cholesterol: Less than 40 mg/dL in men, less than 50 mg/dL in women	2. Risk group: 1-2 factors applicable
Low HDL cholesterol		3. Metabolic syndrome: 3 or more factors applicable
Hypertension	Taking antihypertensive drugs or blood pressure more than 130/85 mmHg
Obesity	Body mass index (BMI): 25 kg/m² or greater

Item	Classification	Frequency	Periodontal disease		χ²
Item	Classification	Frequency	Yes	No	χ²
Sex (n=4,836)	Men	2,090	832 (38.8)	1,258 (60.2)	56.680^***
Sex (n=4,836)	Women	2,746	809 (29.5)	1,937 (70.5)
Age (n=4,836)	Young adults (aged 19-29)	1,292	139 (10.8)	1,153 (89.2)	454.032^***
	Middle-aged adults (aged 30-64)	1,888	721 (38.2)	1,167 (61.8)
	Elderly adults (aged 65 or more)	1,656	781 (47.2)	875 (52.8)
Income level (n=4,807)	Less than KRW1,500,000	1,134	525 (46.3)	609 (53.7)	127.774^***
	KRW1,500,000-4,500,000	2,005	673 (33.6)	1,332 (66.4)
	More than KRW 4,500,000	1,668	429 (25.7)	1,239 (74.3)
Marital status	Single	707	336 (47.5)	371 (52.5)	29.442^***
Marital status	Married	3,342	1,223 (36.6)	2,119 (63.4)
Education (n=4,472)	Elementary school graduate or lower	984	463 (47.1)	521 (52.9)	211.539^***
	Middle school graduate	495	239 (48.3)	256 (51.7)
	High school graduate	1,504	456 (30.3)	1,048 (69.7)
	College graduate or higher	1,489	341 (22.9)	1,148 (77.1)

Item	Classification		Frequency	Periodontal disease		χ²
Item	Classification		Frequency	Yes	No	χ²
Metabolic syndrome factors	Fast blood glucose (n=4,576)	Normal	2,945	833 (28.3)	2,112 (71.7)	116.887^***
	Fast blood glucose (n=4,576)	Abnormal	1,631	719 (44.1)	912 (55.9)
	Hypertriglyceridemia (n=4,576)	Normal	3,205	990 (30.5)	2,260 (69.5)	59.718^***
	Hypertriglyceridemia (n=4,576)	Abnormal	1,326	562 (42.4)	764 (57.6)
	Low HDL cholesterol (n=4,432)	Normal	2,430	725 (29.8)	1,705 (70.2)	37.366^***
	Low HDL cholesterol (n=4,432)	Abnormal	2,002	772 (38.6)	1,230 (61.4)
	Hypertension	Normal	4,097	1,294 (31.6)	2,803 (68.4)	75.381^***
	Hypertension	Abnormal	710	343 (48.3)	367 (51.7)
	Obesity (n=4,827)	Normal	3,129	950 (30.4)	2,179 (45.1)	51.802^***
	Obesity (n=4,827)	Abnormal	1,698	690 (40.6)	1,008 (59.4)

Item	Classification	Frequency	Periodontal disease		χ²
Item	Classification	Frequency	Yes	No	χ²
Metabolic syndrome (n=4,836)	Normal group	1,303	251(19.3)	1,052(80.7)	208.798^***
	Metabolic syndrome risk group	2,374	853(35.9)	1,521(64.1)
	Metabolic syndrome group	1,159	537(46.3)	622(53.7)

Classification	Variables	Model I	Model II
Classification	Variables	OR	OR
Metabolic syndrome	Normal (normal=ref)
	Risk group		1.402^***
	Metabolic syndrome group		1.837^***
Covariates	Sex (women=ref)	1.938^***	1.856^***
	Age	1.463^***	1.409^***
	Income level	0.850^**	0.854^**
	Marital status (single=ref)	0.796^*	0.797^*
	Education	0.861^***	0.883^**
Coefficient		0.484^**	0.352^***
χ²		272.069^***	32.657^***
-2LL		4,668.994	4,636.337
Cox and Snell R²		0.071	0.079
Nagelkerke R²		0.096	0.107
Hosmer and Lemeshow Test (χ²)		11.150	17.326