Relationship between metabolic syndrome and objective masticatory performance in a Japanese general population: The Suita study

Abstract

Objectives

An association between metabolic syndrome (MetS) and periodontal status has recently been focused on. However, no study has investigated the relationship between the prevalence of MetS and the decline of masticatory performance. We aimed to clarify the relationship between MetS and objective masticatory performance using the standardized test food in a general urban Japanese population.

Methods

We studied 1780 Japanese men and women (mean age, 66.5 years) using the Suita study. MetS was defined using the uniform definition proposed in the 2009 Joint Interim Statement. Masticatory performance was evaluated by a chewing test using gummy jelly. Prevalence of MetS among quartiles of masticatory performance was compared using multiple logistic regression analysis adjusting for sex, age, drinking and smoking status, and periodontal status evaluated by the Community Periodontal Index.

Results

Compared to the highest quartile of masticatory performance, the 2nd quartile showed a 1.46-fold increase in the prevalence of MetS (trend P = 0.159). In addition, Analysis by age showed 1.67-, 1.90- and 1.74-fold increases in the prevalence of MetS in the 3rd, 2nd and 1st quartiles among individuals in their 70s, respectively (trend P = 0.094). However, individuals in their 50s and 60s showed no significant relationship between masticatory performance and MetS.

Conclusions

These findings suggested that masticatory performance are inversely associated with the prevalence of MetS independent of periodontal disease, especially in the elderly.

Clinical significance

Declines in objective masticatory performance might be associated with the prevalence of MetS, independent of periodontitis. Given our results, treatments aimed at maintaining and recovering masticatory performance may represent important dental care to mitigate the risk of MetS.

Introduction

Metabolic syndrome (MetS) is a complex disorder characterized by abdominal obesity, elevated blood pressure, high fasting plasma glucose, and hyperlipidemia . Preventing MetS is important, because each of the components of this syndrome have been associated with cardiovascular disease . The prevalence of MetS is increasing worldwide , including in Japan .

Recent studies have shed light on the association oral health status and MetS. Previous studies have reported relationships between periodontal disease and MetS or its components. Furthermore, some reports showed the relationships between tooth loss and MetS . Destruction of periodontal tissue with the progression of periodontal disease has been shown to influence masticatory performance . In addition, tooth loss causes declines in occlusal support, masticatory performance and oral function . However, previous studies focused on the relationships of chronic inflammation to periodontal disease or tooth loss, and no study has investigated relationships with the decline of masticatory performance caused by periodontal disease and tooth loss.

The purpose of the present study was therefore to investigate the association between MetS and masticatory performance as a measure of oral function. This study assessed the hypothesis that the prevalence of MetS is inversely associated with objective masticatory performance in a general urban Japanese population.

Materials and methods

Study participants

The Suita study is a population-based cohort study of cardiovascular disease; details of the study design have been described elsewhere . We recruited 2083 subjects to both medical check-ups and dental examinations between June 2008 and November 2013. Of these, 251 individuals were excluded due to with non-fasting blood collection (n = 109), incomplete masticatory performance data (n = 80) and incomplete periodontal data (n = 114). Finally, 1780 subjects (743 men, 1037 women; mean age, 66.5 ± 7.9 years) were included in the study. The study protocol was approved by the ethics committee of the National Cerebral and Cardiovascular Center (M19-62). Written, informed consent was obtained from all participants.

Medical examination

Well-trained nurses measured blood pressure twice in a seated position using an automated sphygmomanometer (Colin BP-I03ill; Omron, Kyoto, Japan) and an appropriately sized cuff according to a standard protocol after at least 5 min of rest before the initial blood pressure reading was obtained. Systolic blood pressure (SBP) and diastolic blood pressures (DBP) were considered as the average of 2 measurements recorded >1 min apart .

Routine blood tests were performed at baseline examination, including triglycerides, high-density lipoprotein (HDL) cholesterol, and fasting blood glucose. MetS was defined using the uniform definition proposed in the 2009 Joint Interim Statement . Each component of MetS was defined as follows: high blood pressure (SBP ≥130 mmHg and/or DBP ≥85 mmHg, and/or taking antihypertensive medication), low serum HDL cholesterol ( < 40 mg/dL in men, <50 mg/dL in women), hypertriglyceridemia (triglycerides ≥150 mg/dL, and/or taking antihyperlipidemia medication), high plasma glucose (fasting blood glucose ≥100 mg/dL, and/or undergoing diabetic therapy), and abdominal obesity as measured by waist circumference (waist circumference: ≥90 cm in men; ≥80 cm in women) in the Asia diagnostic criteria .

MetS was defined as the presence of any three or more of the five components.

Dental examination

Periodontal tissue examination

Periodontal status was assessed using the Community Periodontal Index (CPI) by means of records of 10 index teeth. Ten teeth were examined in total, comprising 8 designated molars (first and second molars) and 2 incisors (upper right and left central incisors), and when this test could not be performed because of the loss of one or both of the central incisors concerned, the same tooth on the opposite side was examined . No evaluation was performed when all relevant teeth were missing. Periodontal status was examined using a CPI probe (YDM, Tokyo, Japan) to evaluate each tooth with respect to six periodontal pockets according to the following criteria, and the highest-value code was recorded. CPI codes were as follows: Code 0, no sign of gingival inflammation; Code 1, evident bleeding after probing; Code 2, deposits of dental calculus (including those detected by probing up to 4 mm beneath the gingival margin); Code 3, periodontal pocket depth ≥4 mm, but <6 mm; and Code 4, periodontal pocket depth ≥6 mm. This examination was performed by five dentists who had undergone calibration in advance. Cohen’s κ value for the consistency between periodontal tissue examinations by the five dentists was 0.78. In our study, periodontitis was defined as CPI Code ≥3.

Masticatory performance

Masticatory performance was determined from the concentration of dissolved glucose obtained from test gummy jelly (20 × 20 × 10 mm, 5.5 g; UHA Mikakuto, Osaka, Japan), as a standardized food developed for measuring masticatory performance . Subjects were instructed to chew jelly using 30 chewing strokes on the preferred chewing side (right, left, or both sides), and to expectorate the bolus of comminuted particles as thoroughly as possible. The cotton gauze and comminuted particles were then rinsed under running water for 30 s in order to remove saliva and glucose adhering to their surfaces. The comminuted jelly alone was subsequently placed in a plastic container, and water (35 °C, 15 mL) was injected into this container, and the contents were agitated for 10 s with a magnetic stirrer (400 rpm, PC-410D Digital Stirrer; Corning, Tewksbury, MA). Immediately after this agitation, a small amount of supernatant was collected using forceps and placed in contact with the tip of a sensor fitted to a commercially available instrument for self-monitoring blood glucose (Glutest Every; Sanwa Chemical Laboratory, Nagoya, Japan), and the glucose concentration displayed after 15 s was recorded. The increase in the surface area of comminuted jelly was calculated from the glucose concentration using a regression formula (y = 15x − 250), and this was regarded as masticatory performance . Participants who wore removable prostheses kept their denture in place during measurements.

Lifestyle variables

Information on lifestyle was collected using normalized questionnaires by well-trained nurses through interviews, including drinking and smoking habits. Drinking status was divided into never drinker, former drinker, or current drinker and smoking status was divided into never smoker, former smoker, or current smoker, respectively.

Statistical analysis

We divided subjects into four groups by quartile of masticatory performance. First, we evaluated each component of MetS, smoking and drinking status, and the prevalence of periodontal disease in each group. Second, we expressed odds ratios (ORs) and 95% confidence intervals (95%CIs) for the prevalence of MetS among quartile groups by logistic regression analyses adjusted for sex, age, smoking and drinking status, and periodontal status as covariates in multivariate analysis. In addition, we divided subjects by age into four groups by quartile of masticatory performance of the all subjects and investigated the association between MetS and masticatory performance, with multivariate adjustments for sex, age, smoking and drinking status, and periodontal status. Values of P < 0.05 were considered significant for all comparisons. All analyses were performed using PASW Statistic 21 (SPSS; IBM, Tokyo, Japan).

Materials and methods

Study participants

The Suita study is a population-based cohort study of cardiovascular disease; details of the study design have been described elsewhere . We recruited 2083 subjects to both medical check-ups and dental examinations between June 2008 and November 2013. Of these, 251 individuals were excluded due to with non-fasting blood collection (n = 109), incomplete masticatory performance data (n = 80) and incomplete periodontal data (n = 114). Finally, 1780 subjects (743 men, 1037 women; mean age, 66.5 ± 7.9 years) were included in the study. The study protocol was approved by the ethics committee of the National Cerebral and Cardiovascular Center (M19-62). Written, informed consent was obtained from all participants.

Medical examination

Well-trained nurses measured blood pressure twice in a seated position using an automated sphygmomanometer (Colin BP-I03ill; Omron, Kyoto, Japan) and an appropriately sized cuff according to a standard protocol after at least 5 min of rest before the initial blood pressure reading was obtained. Systolic blood pressure (SBP) and diastolic blood pressures (DBP) were considered as the average of 2 measurements recorded >1 min apart .

Routine blood tests were performed at baseline examination, including triglycerides, high-density lipoprotein (HDL) cholesterol, and fasting blood glucose. MetS was defined using the uniform definition proposed in the 2009 Joint Interim Statement . Each component of MetS was defined as follows: high blood pressure (SBP ≥130 mmHg and/or DBP ≥85 mmHg, and/or taking antihypertensive medication), low serum HDL cholesterol ( < 40 mg/dL in men, <50 mg/dL in women), hypertriglyceridemia (triglycerides ≥150 mg/dL, and/or taking antihyperlipidemia medication), high plasma glucose (fasting blood glucose ≥100 mg/dL, and/or undergoing diabetic therapy), and abdominal obesity as measured by waist circumference (waist circumference: ≥90 cm in men; ≥80 cm in women) in the Asia diagnostic criteria .

MetS was defined as the presence of any three or more of the five components.

Dental examination

Periodontal tissue examination

Periodontal status was assessed using the Community Periodontal Index (CPI) by means of records of 10 index teeth. Ten teeth were examined in total, comprising 8 designated molars (first and second molars) and 2 incisors (upper right and left central incisors), and when this test could not be performed because of the loss of one or both of the central incisors concerned, the same tooth on the opposite side was examined . No evaluation was performed when all relevant teeth were missing. Periodontal status was examined using a CPI probe (YDM, Tokyo, Japan) to evaluate each tooth with respect to six periodontal pockets according to the following criteria, and the highest-value code was recorded. CPI codes were as follows: Code 0, no sign of gingival inflammation; Code 1, evident bleeding after probing; Code 2, deposits of dental calculus (including those detected by probing up to 4 mm beneath the gingival margin); Code 3, periodontal pocket depth ≥4 mm, but <6 mm; and Code 4, periodontal pocket depth ≥6 mm. This examination was performed by five dentists who had undergone calibration in advance. Cohen’s κ value for the consistency between periodontal tissue examinations by the five dentists was 0.78. In our study, periodontitis was defined as CPI Code ≥3.

Masticatory performance

Masticatory performance was determined from the concentration of dissolved glucose obtained from test gummy jelly (20 × 20 × 10 mm, 5.5 g; UHA Mikakuto, Osaka, Japan), as a standardized food developed for measuring masticatory performance . Subjects were instructed to chew jelly using 30 chewing strokes on the preferred chewing side (right, left, or both sides), and to expectorate the bolus of comminuted particles as thoroughly as possible. The cotton gauze and comminuted particles were then rinsed under running water for 30 s in order to remove saliva and glucose adhering to their surfaces. The comminuted jelly alone was subsequently placed in a plastic container, and water (35 °C, 15 mL) was injected into this container, and the contents were agitated for 10 s with a magnetic stirrer (400 rpm, PC-410D Digital Stirrer; Corning, Tewksbury, MA). Immediately after this agitation, a small amount of supernatant was collected using forceps and placed in contact with the tip of a sensor fitted to a commercially available instrument for self-monitoring blood glucose (Glutest Every; Sanwa Chemical Laboratory, Nagoya, Japan), and the glucose concentration displayed after 15 s was recorded. The increase in the surface area of comminuted jelly was calculated from the glucose concentration using a regression formula (y = 15x − 250), and this was regarded as masticatory performance . Participants who wore removable prostheses kept their denture in place during measurements.

Lifestyle variables

Information on lifestyle was collected using normalized questionnaires by well-trained nurses through interviews, including drinking and smoking habits. Drinking status was divided into never drinker, former drinker, or current drinker and smoking status was divided into never smoker, former smoker, or current smoker, respectively.

Statistical analysis

We divided subjects into four groups by quartile of masticatory performance. First, we evaluated each component of MetS, smoking and drinking status, and the prevalence of periodontal disease in each group. Second, we expressed odds ratios (ORs) and 95% confidence intervals (95%CIs) for the prevalence of MetS among quartile groups by logistic regression analyses adjusted for sex, age, smoking and drinking status, and periodontal status as covariates in multivariate analysis. In addition, we divided subjects by age into four groups by quartile of masticatory performance of the all subjects and investigated the association between MetS and masticatory performance, with multivariate adjustments for sex, age, smoking and drinking status, and periodontal status. Values of P < 0.05 were considered significant for all comparisons. All analyses were performed using PASW Statistic 21 (SPSS; IBM, Tokyo, Japan).

Results

The baseline characteristics of the study according to quartile groups of masticatory performance are shown in Table 1 . Compared to the highest quartile of masticatory performance (Q4), another three quartiles (Q1–3) were significantly older. In addition, the first quartile showed the highest prevalence of periodontal disease among the quartiles.

Table 1
Characteristics of study subjects.
Characteristic Masticatory performance
Q1 (lowest) Q2 Q3 Q4 (highest)
Number 448 443 446 443
Age, years 68.7 ± 7.4 a 66.2 ± 7.7 a 66.3 ± 7.8 a 64.6 ± 7.9
Men, % 41.7 36.6 41.7 47.0
Waist circumference, cm 83.9 ± 9.2 83.4 ± 9.1 84.1 ± 8.9 83.1 ± 8.5
Blood pressure
SBP, mmHg 130.3 ± 19.7 127.8 ± 19.6 128.7 ± 20.1 126.9 ± 18.9
DBP, mmHg 78.2 ± 10.7 77.2 ± 11.3 78.4 ± 11.2 77.5 ± 11.2
Fasting blood glucose, mg/dL 106.4 ± 24.3 103.0 ± 15.3 104.0 ± 16.9 103.5 ± 16.4
HDL cholesterol, mg/dL 60.7 ± 16.3 61.5 ± 15.9 62.3 ± 15.7 64.0 ± 15.8
Triglycerides, mg/dL 104.3 ± 58.3 104.7 ± 57.9 105.6 ± 58.4 101.5 ± 59.2
Smoking status, %
Current 9.8 11.5 7.6 9.9
Quitting 30.1 21.2 26.7 30.7
Never 60.0 67.3 65.7 59.4
Drinking status, %
Current 42.2 40.4 41.7 55.1
Quitting 4.9 3.4 4.3 1.8
Never 52.9 56.2 54.0 43.1
Masticatory performance, mm 2 2228 ± 838 a 3930 ± 348 a 5171 ± 354 a 6915 ± 862
Periodontal disease, % 56.3 51.0 51.3 43.6
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Jun 19, 2018 | Posted by in General Dentistry | Comments Off on Relationship between metabolic syndrome and objective masticatory performance in a Japanese general population: The Suita study
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