Volume 75, Issue 1, Pages 72-80 (January 2007)

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Appropriate waist circumference cutoff points for central obesity in Korean adults☆

Received 9 March 2006; accepted 24 April 2006. published online 30 May 2006.

Abstract

Background

The International Diabetes Federation consensus recently proposed a new definition for the diagnosis of metabolic syndrome, incorporating ethnically specific waist circumference (WC) cutoff points.

Objective

We investigated the ethnically appropriate WC cutoff values for central obesity in Korean adults to predict increased risk of elevated triacylglycerol, reduced HDL cholesterol, elevated blood pressure, elevated fasting plasma glucose, or two or more of these factors.

Design

We used data from 6561 adults, aged 20–80 years, who participated in the Korean Health and Nutritional Examination Survey of 1998, a cross-sectional health survey of a nationally representative sample of Koreans.

Results

Based on the receiver operating characteristic curve analysis, the WC value for predicting metabolic risk factors in Koreans was about 85cm for men and 80cm for women. The odds ratio for the risk of two or more metabolic risk factors increased abruptly in men with WC≥90cm and women with WC≥85cm. The 80th percentile for WC in the Korean population was 90cm for men and 86.5cm for women. Thus, the appropriate WC cutoff point for central obesity in Koreans was determined to be 90cm for men and 85cm for women.

Conclusions

Based on our criteria, the prevalence of central obesity was 19.8% in Korean men and 24.5% in Korean women. These findings suggest the applicability of ethnically specific cutoff points for WC in assessing central obesity.

Keywords: Obesity, Waist circumference, Cutoff points, Metabolic syndrome, Central obesity, Korean

Article Outline

• Abstract

• 1. Introduction

• 2. Methods

• 2.1. Study population

• 2.2. Anthropometric measurements and metabolic risk factors

• 2.3. Definition of metabolic risk factors

• 2.4. Assessment of other covariates

• 2.5. Statistical analysis

• 3. Results

• 3.1. Basic characteristics of the study subjects

• 3.2. Metabolic risk factors according to waist circumference category

• 3.3. Values of waist circumference for detecting metabolic risk factors analyzed by the receiver operating characteristic with highest sensitivity and specificity

• 3.4. Cutoff points of waist circumference for predicting metabolic risk factors analyzed by adjusted odds ratios

• 4. Discussion

• Acknowledgment

• References

• Copyright

1. Introduction

Metabolic syndrome is closely related to increased cardiovascular morbidity and mortality [1]. In 2005, the International Diabetes Federation (IDF) in a global consensus statement formulated a new, clinically accessible, worldwide definition of metabolic syndrome [2] built on earlier definitions formulated by the World Health Organization (WHO) [3] and the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel, ATP III) [4]. The IDF defined metabolic syndrome as central obesity plus two of the following four additional factors: elevated plasma triacylglycerol, reduced HDL cholesterol, elevated blood pressure, and elevated fasting plasma glucose [2].

A prominent feature of the IDF definition is that central obesity is an essential, not an optional, component of metabolic syndrome, with central obesity defined according to ethnically specific values of waist circumference (WC) [2]. The cutoff point for central obesity in the United States was defined as ≥102cm for men and ≥88cm for women [4], whereas, for Europeans, the cutoff was ≥94cm for men and ≥80cm for women [5]. Asians are more prone to obesity-related co-morbidities than Caucasians, even at lower BMI and/or smaller WC values [6], [7]. Therefore, cutoff values of ≥90cm for men and ≥80cm for women were adopted for South Asians and Chinese [8], and the Japanese used cutoff points of ≥85cm for men and ≥90cm for women [9].

Using the NCEP ATP III definition of central obesity [5] (men, >102cm; women, >88cm), the prevalence of central obesity in Korea was only 1.3% for men and 15.3% for women [10], whereas the prevalence of central obesity among US adults was 29.8% in men and 46.3% in women [11]. Using Asian-Pacific guidelines for central obesity [8] (men, >90cm; women, >80cm), the prevalence of central obesity in Korea was 19.5% in men and 39.0% in women [12]. These findings suggest the importance of applying ethnically appropriate cutoff values of WC for assessing central obesity. In agreement with the IDF proposal, the Committee on Metabolic Syndrome of the Korean Society for the Study of Obesity (KSSO) investigated the appropriate WC cutoff points for central obesity in Koreans.

2. Methods

2.1. Study population

The Korean Ministry of Health and Welfare conducted the Korean National Health and Nutrition Examination Survey of noninstitutionalized Korean civilians in 1998. A stratified, multistage probability sampling design was used, with selections made from sampling units based on geographic area, sex, and age groups using household registries. The staff conducted surveys in households and administered questionnaires, which included the demographic, socioeconomic, dietary, and medical history of each respondent. The study was performed according to the guidelines of the Helsinki Declaration.

In total, 10,876 persons were identified to take part in the survey. Anthropometric measurements were missing for 1105 respondents, and 1306 individuals did not properly fast prior to the blood test. Thus, complete data were obtained for 8465 participants, whose mean age (men, 38.4 years; women, 40.4 years) was similar to that of the initial 10,876 individuals recruited for the survey (men, 36.4 years; women, 38.1 years). Data from 6561 subjects, composed of 2930 men and 3631 women between the ages of 20 and 80 years, were included in the present analysis.

2.2. Anthropometric measurements and metabolic risk factors

Anthropometric measurements of individuals wearing light clothing and without shoes were conducted by well-trained examiners. Height was measured to the nearest 0.1cm using a portable stadiometer (850–2060mm; Seriter, Bismarck, ND, USA). Weight was measured in the upright position to the nearest 0.1kg using a calibrated balance beam scale (Giant-150N; HANA, Seoul, Korea). Body mass index (BMI) was calculated by dividing weight (kg) by height squared (m2). The WC measurements were taken at the end of normal expiration and to the nearest 0.1cm, measuring from the narrowest point between the lower borders of the rib cage and the iliac crest.

A mercury sphygmomanometer (Baumanometer; WA Baum, Copiague, NY, USA) was used to measure the blood pressure of each subject in the sitting position after a 10-min rest period. During the 30min preceding the measurement, the subjects were required to refrain from smoking or consuming caffeine. The appearance of the first sound (phase 1 Korotkoff sound) was used to define systolic blood pressure, and the disappearance of sound (phase 5 Korotkoff sound) was used to define diastolic blood pressure [13]. Two readings each of systolic and diastolic blood pressures were recorded, and the average of each measurement was used for data analysis. If the first two measurements differed by more than 5mmHg, additional readings were taken.

Blood samples were obtained from an antecubital vein into vacutainer tubes containing EDTA in the morning after an overnight fasting period. The samples were subsequently analyzed at a central, certified laboratory. Plasma glucose, total cholesterol, triacylglycerol, and HDL cholesterol were measured using an autoanalyzer (Hitachi 747; Hitachi, Tokyo, Japan).

2.3. Definition of metabolic risk factors

We used the criteria for metabolic risk factors proposed by the IDF [2]: elevated triacylglycerol, ≥150mg/dL (≥1.7mmol/L); reduced HDL cholesterol, <40mg/dL (<1.03mmol/L) for men and <50mg/dL (<1.29mmol/L) for women; elevated blood pressure, systolic ≥130mmHg, diastolic ≥85mmHg, or treatment for previously diagnosed hypertension; elevated fasting plasma glucose, ≥100mg/dL (≥5.6mmol/L) or previously diagnosed type 2 diabetes; and a combination of two or more of these risk factors.

2.4. Assessment of other covariates

The measurements of other covariates and potential confounders were collected for the participants. Self-reported education level, alcohol consumption, and smoking were estimated from the questionnaire. Education level was categorized into three groups: ≤9 years, 10–12 years, and >12 years. Alcohol consumption was estimated from the usual daily intake of alcoholic beverages, and drinkers were divided into three groups by the amount of alcohol consumed: <10, 10–30, and ≥30g/day. Participants were classified into three groups based on smoking status: current smoker, ex-smoker, or nonsmoker.

2.5. Statistical analysis

The statistical analysis was conducted using SPSS version 11.0 for Windows (SPSS Inc., Chicago, IL, USA). Continuous variables were expressed as gender-specific means and standard deviations, and discrete variables were expressed as gender-specific proportions. The sensitivity and specificity of each WC category in detecting the presence of reduced HDL cholesterol; elevated triacylglycerol, blood pressure, and fasting plasma glucose; and two or more risk factors were calculated by creating dichotomous variables for each WC value. Additionally, the distance on the receiver operating characteristic (ROC) curve for each WC value was calculated by plotting the true-positive rate (sensitivity) against the false-positive rate (1—specificity). The Yuden index was used for determining the appropriate WC cutoff points [14].

To identify the appropriate WC values for predicting metabolic risk factors in men and women, the odds ratios (ORs) were calculated using multiple logistic regression analysis with adjustments for age, socioeconomic status, and lifestyle factors. In all analyses, the WC values were categorized by 5-cm increments, using <70cm as a WC referent. The adjusted ORs are presented together with their 95% confidence intervals (CI). The linear trend in odds ratios across WC categories was evaluated using the likelihood ratio test. All analyses were two-tailed, and P<0.05 was considered statistically significant.

3. Results

3.1. Basic characteristics of the study subjects

The basic characteristics of the study subjects and the prevalence of metabolic risk factors are shown in Table 1. The mean age of all participants was 45.1 years, and the mean BMI was 23.2kg/m2. The mean waist circumference was 82.8cm in men and 78.6cm in women. Almost 26% of men and 16% of women had >12 years of education. About 66% of the men and 7% of the women were smokers. Twenty-two percent of the men and 1% of the women consumed more than 30g of alcohol per day.

Table 1.

Basic characteristics of the study population in the Korean National Health and Nutrition Examination Survey of 1998


	Men (n=2930)	Women (n=3631)	Total (n=6561)
Age (years)a	44.5±0.3	45.5±0.3	45.1±0.2
Body mass index (kg/m2)a	23.1±0.1	23.3±0.1	23.2±0.4
Waist circumference (cm)a	82.8±0.2	78.6±0.2	80.4±0.2
Education (%)
≤9 years	36.1	53.0	45.5
10–12 years	37.8	30.7	33.8
>12 years	26.1	16.3	20.7

Smoking (%)
Current smoker	65.5	6.7	32.8
Ex-smoker	17.2	2.5	9.0
Nonsmoker	17.3	90.8	58.2

Alcohol consumption (%)
<10g/day	50.1	92.9	73.9
10–30g/day	28.2	6.0	15.8
≥30g/day	21.7	1.1	10.3

Metabolic risk factors (%)
Elevated triacylglycerol	36.3	22.8	28.9
Reduced HDL cholesterol	25.4	48.4	38.1
Elevated blood pressure	42.7	32.2	36.9
Elevated fasting plasma glucose	41.6	37.6	39.4
≥2 risk factors	46.6	43.0	44.6

Metabolic risk factors were defined according to IDF criteria [2]. Elevated triacylglycerol, ≥150mg/dL (≥1.7mmol/L); reduced HDL cholesterol, <40mg/dL (<1.03mmol/L) for men and <50mg/dL (<1.29mmol/L) for women; elevated blood pressure: systolic blood pressure≥130mmHg, diastolic blood pressure≥85mmHg, or treatment for previously diagnosed hypertension; elevated fasting plasma glucose, ≥100mg/dL (≥5.6mmol/L) or previously diagnosed type 2 diabetes; and a combination of two or more of these metabolic risk factors.

The values are represented as means±S.E.

Elevated triacylglycerol was detected in 36.3% of the men and 22.8% of the women, reduced HDL cholesterol was observed in 25.4% of the men and 48.4% of the women, elevated blood pressure was detected in 42.7% of the men and 32.2% of the women, and elevated fasting plasma glucose or previously diagnosed type 2 diabetes was observed in 41.6% of the men and 37.6% of the women. Two or more metabolic risk factors were present in 46.6% of the men and 43.0% of the women.

3.2. Metabolic risk factors according to waist circumference category

In both men and women, mean triacylglycerol, systolic blood pressure, diastolic blood pressure, and fasting plasma glucose values increased linearly with increasing WC values; and HDL cholesterol values linearly decreased with increasing WC values (Table 2). When the continuous risk factors were categorized, reduced HDL cholesterol; elevated plasma triacylglycerol, blood pressure, and fasting plasma glucose; and two or more metabolic risk factors showed higher prevalence in categories of higher WC values for both men and women. The proportion of individuals with two or more metabolic risk factors was increased about fourfold in men and fivefold in women going from WC values of <70 to ≥95cm (Table 3).

Table 2.

Mean values for metabolic risk factors according to waist circumference category among Korean men and women (Korean National Health and Nutrition Examination Survey of 1998)


Metabolic risk factors	Waist circumference category (cm)
	<70 (n=156)	70–75 (n=381)	75–80 (n=573)	80–85 (n=671)	85–90 (n=560)	90–95 (n=370)	≥95 (n=219)
Men
Triacylglycerol	101.2±3.9	105.7±2.7	119.9±2.4	136.3±2.5	151.4±2.7	162.7±3.5	168.1±4.7
HDL cholesterol	54.0±1.1	52.7±0.7	50.6±0.5	47.9±0.5	45.1±0.4	44.2±0.6	43.2±0.7
Systolic blood pressure	124.6±2.9	123.8±0.8	124.4±0.7	127.9±0.7	129.5±0.8	134.1±1.0	135.9±1.1
Diastolic blood pressure	76.4±0.9	76.7±0.6	79.2±1.5	80.8±0.5	83.1±0.5	85.3±0.7	88.5±0.7
Fasting plasma glucose	96.6±2.0	97.4±1.7	98.5±1.1	101.2±1.2	103.7±1.2	107.7±1.8	108.4±2.0

	<70 (n=721)	70–75 (n=705)	75–80 (n=681)	80–85 (n=619)	85–90 (n=459)	90–95 (n=238)	≥95 (n=208)
Women
Triacylglycerol	83.6±1.5	98.2±1.9	109.5±2.0	127.2±2.3	134.6±2.8	139.9±3.9	148.2±3.7
HDL cholesterol	56.4±0.5	53.3±0.5	51.2±0.5	48.7±0.5	48.3±0.6	48.5±0.8	47.1±0.8
Systolic blood pressure	115.2±0.6	117.7±0.7	124.4±1.0	127.1±0.8	131.9±1.0	137.1±1.5	138.6±1.5
Diastolic blood pressure	71.7±0.4	74.3±0.9	76.4±0.8	78.3±0.5	80.5±0.5	82.0±0.8	83.2±0.8
Fasting plasma glucose	92.6±0.7	95.2±1.0	99.7±1.3	103.2±1.4	106.9±1.9	113.7±2.5	112.1±2.7

All values are means±S.E.

Table 3.

Prevalence of metabolic risk factors according to waist circumference category among Korean men and women (Korean National Health and Nutrition Examination Survey of 1998)


Metabolic risk factors	Waist circumference category (cm)
	<70 (n=156)	70–75 (n=381)	75–80 (n=573)	80–85 (n=671)	85–90 (n=560)	90–95 (n=370)	≥95 (n=219)
Men
Elevated triacylglycerol	14.7	16.8	26.7	35.5	46.4	54.9	56.6
Reduced HDL cholesterol	10.3	14.2	18.8	26.1	32.1	35.9	35.2
Elevated blood pressure	26.9	27.8	32.8	42.5	46.6	57.8	70.8
Elevated fasting plasma glucose	28.2	31.8	37.2	39.2	47.9	50.8	55.3
≥2 risk factors	21.2	23.4	33.3	46.8	57.0	67.8	76.7

	<70 (n=721)	70–75 (n=705)	75–80 (n=681)	80–85 (n=619)	85–90 (n=459)	90–95 (n=238)	≥95 (n=208)
Women
Elevated triacylglycerol	7.1	13.9	19.4	31.2	32.9	42.0	50.0
Reduced HDL cholesterol	30.4	41.3	48.0	59.1	59.7	60.9	65.4
Elevated blood pressure	13.3	19.0	30.4	37.6	49.2	59.2	63.9
Elevated fasting plasma glucose	22.5	28.5	37.2	42.2	51.9	55.9	56.3
≥2 risk factors	15.8	27.8	40.7	56.2	63.8	71.8	77.4

3.3. Values of waist circumference for detecting metabolic risk factors analyzed by the receiver operating characteristic with highest sensitivity and specificity

The population percentile for each WC cutoff as well as the sensitivity, specificity, and Yuden index for detecting metabolic risk factors are presented separately for men and women in Table 4. The specificity, sensitivity, and Yuden index were similar for all metabolic risk factors between men and women. For all of the risk factors, the point at which sensitivity equaled specificity was at WC values of about 80–85cm in men and about 75–80cm in women. The 80th percentile for WC values was estimated as 90cm in men and 86.5cm in women.

Table 4.

The population percentile for each WC cutoff and the sensitivity, specificity, and Yuden index for detection of metabolic risk factors among Korean men and women (Korean National Health and Nutrition Examination Survey of 1998)


WC cutoff (cm)	Percentile	Elevated triacylglycerol			Reduced HDL cholesterol			Elevated blood pressure			Elevated fasting glucose			Two or more risk factors
		Sensitivity	Specificity	Yuden index	Sensitivity	Specificity	Yuden index	Sensitivity	Specificity	Yuden index	Sensitivity	Specificity	Yuden index	Sensitivity	Specificity	Yuden index
Men
60	0.1	100.0	0.1	0.1	100.0	0.1	0.1	99.9	0.1	0.0	99.8	0.0	−0.2	99.9	0.1	0.0
65	1.1	99.5	1.4	0.9	99.7	1.3	1.0	99.4	1.4	0.8	99.2	1.2	0.4	99.5	1.5	1.0
70	5.6	97.7	7.5	5.2	97.6	6.6	4.2	96.6	7.2	3.8	96.4	7.0	3.4	97.5	8.2	5.7
75	18.8	91.7	24.8	16.5	90.3	21.9	12.2	87.7	23.6	11.3	86.1	22.3	8.4	90.8	27.2	18.0
80	38.1	77.4	47.0	24.4	75.6	42.8	18.4	72.9	46.3	19.2	68.6	42.9	11.5	76.8	51.1	27.9
85	61.2	54.6	70.3	24.9	51.7	65.6	17.3	49.8	69.4	19.2	47.0	67.1	14.1	53.6	74.1	27.7
90	80.2	30.4	86.2	16.6	28.0	82.9	10.9	29.3	87.2	16.5	25.3	84.1	9.4	30.5	89.5	20.0
95	92.8	11.0	94.9	5.9	9.8	93.6	3.4	11.8	96.2	8.0	9.5	94.4	3.9	11.8	96.7	8.5
100	97.6	4.3	98.7	3.0	3.6	98.0	1.6	4.6	99.2	3.8	3.0	98.0	1.0	4.2	99.2	3.4

Women
60	0.6	99.9	0.8	0.7	99.7	0.9	0.6	99.7	0.7	0.4	99.3	0.6	−0.1	99.7	0.9	0.6
65	6.1	98.7	7.5	6.2	96.4	8.4	4.7	97.8	7.9	5.7	96.1	7.4	3.5	98.0	9.2	7.2
70	20.4	93.7	24.6	18.3	87.3	27.5	14.8	91.5	26.0	17.5	87.9	25.4	13.3	92.6	30.2	22.8
75	39.8	81.4	46.1	27.5	70.6	49.6	20.2	79.9	49.2	29.1	73.0	47.5	20.5	79.7	54.5	34.2
80	58.5	65.7	65.7	31.4	51.9	68.3	20.2	62.2	68.4	30.6	54.4	66.3	20.7	62.0	74.0	36.0
85	75.5	42.5	80.8	23.3	31.3	81.8	13.1	42.6	84.0	26.6	35.2	81.9	17.1	39.8	87.0	26.8
90	87.9	24.2	91.4	15.6	15.8	91.3	7.1	23.1	93.1	16.2	18.2	91.5	9.7	21.0	94.5	15.5
95	94.5	11.9	96.4	8.3	7.5	96.3	3.8	10.9	97.0	7.9	8.4	96.2	4.6	9.9	97.7	7.6
100	97.7	5.1	98.6	3.7	3.3	98.7	2.0	4.3	98.7	3.0	3.4	98.4	1.8	3.9	99.0	2.9

3.4. Cutoff points of waist circumference for predicting metabolic risk factors analyzed by adjusted odds ratios

The odds ratios for predicting the presence of metabolic risk factors according to WC values categorized by 5-cm increments in men and women are shown in Fig. 1. Based on a 70-cm WC, the odds ratio for predicting metabolic risk factors increased with each 5-cm increment in WC. The increase in the OR according to WC categories was significant after adjusting for age, socioeconomic status, and lifestyle factors in men and women, respectively. The odds ratio for the presence of two or more metabolic risk factors increased abruptly in men with WC≥90cm and women with WC≥85cm.

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Fig. 1. Odds ratios (OR) adjusted for age, socioeconomic status, and lifestyle factors for predicting the presence of elevated triacylglycerol, reduced HDL cholesterol, elevated blood pressure, elevated fasting plasma glucose, and two or more risk factors according to WC categories, with WC<70cm as a reference level, in men and women, respectively (Korean National Health and Nutrition Examination Survey of 1998). P<0.001 by likelihood ratio test for increase in OR according to WC categories. Abbreviations: WC, waist circumference; TG, triacylglycerol; HDL-C, high density lipoprotein cholesterol; BP, blood pressure; FPG, fasting plasma glucose.

4. Discussion

Since Reaven first suggested a definition of metabolic syndrome in 1988 [15], many diagnostic criteria have been established for metabolic syndrome, including those proposed by the WHO [3], NCEP ATP III [4], European Group for the Study of Insulin Resistance (EGIR) [5], American Association of Clinical Endocrinologists (AACE) [16], and IDF [2]. The pathophysiology of metabolic syndrome was focused primarily on insulin resistance and hyperinsulinemia, but the importance of metabolic risk factors and central obesity has been recognized recently.

The IDF proposed that central obesity, as assessed by WC cutoff values specific for ethnicity and gender, should be an essential component for the diagnosis of metabolic syndrome. In agreement with the IDF proposal, we propose WC values of 90cm for men and 85cm for women as appropriate cutoff points for central obesity in Korean adults. These results are concordant with our previous study [17].

According to our criteria, the prevalence of central obesity was 19.8% in men and 24.5% in women. Our results demonstrated a difference of 5cm in the cutoff point between men and women; this gap is much smaller than in Americans, Europeans, South Asians, or Chinese. According to the WC criteria for central obesity in American (>102cm), European (≥94cm), and Japanese men (≥85cm), the prevalence of central obesity in Koreans would be 1.4%, 9.3%, and 38.8%, respectively. Moreover, according to the WC criteria for central obesity in European, South Asian, and Chinese women (≥80cm), the prevalence of central obesity in Koreans would be 41.5%. Considering the actual prevalence of central obesity in the population, these specific criteria for central obesity are inappropriate for Koreans.

To determine the WC standard for central obesity in Westerners, the WC values corresponding to BMI values of 25kg/m2 (WC: men, 94cm; women, 80cm) and 30kg/m2 (WC: men, 102cm; women, 88cm) were used [18]. At those WC values, prominent increases occurred in the prevalence of cardiovascular risk factors such as hypertension, hypercholesterolemia, and low HDL cholesterol; thus, those two sets of WC values were established, respectively, as “action level 1” and “action level 2” with regard to cardiovascular risk in Westerners [19].

A recent cohort study among US men over the last 13 years has suggested that the currently recommended WC cutoff point of 102cm for men may need to be reevaluated; a lower cutoff value may be more appropriate in predicting the risk for type 2 diabetes [20]. Another recent study on central obesity in Westerners found different sets of WC values associated with increased risk for cardiovascular disease at the designated BMI values: 90cm for men and 83cm for women at 25kg/m2 BMI, and 100cm for men and 93cm for women at 30kg/m2 BMI [21]. Furthermore, it has been shown that the existing WC criteria cannot be properly applied in the elderly because of the concentration of body fat in seniors [22].

The WHO experts concluded that the proportion of Asian people at high risk for cardiovascular disease is substantial at BMI values lower than the existing WHO cutoff point for overweight [23]. Regression analysis of our data revealed that the WC value corresponding to a BMI of 25kg/m2, which is the cutoff for obesity in Asians, is about 90cm for men and about 85cm for women (data not shown). Others have also suggested that the current overweight and central adiposity guidelines based on Western populations are not appropriate for Asian populations [24], [25], [26]. The report of the joint WHO/IASO/IOTF committee proposed the WC values of 90cm for men and 80cm for women as Asian-specific WC cutoff points for central obesity [8]; these are the values that were adopted as the criteria for South Asians and Chinese in the IDF consensus.

According to the criteria, the WC cutoff point for men is 10cm greater than that for women. However, our study resulted in a cutoff value for men 5cm greater than for women among Korean adults. A recent study in Chinese adults aged 35–74 years suggested the same WC value, 80cm, for both men and women as the cutoff point for central obesity in identifying cardiovascular risk factors [27]. Reports by others have suggested a WC cutoff point near 80–85cm for men and 75–80cm for women, supporting a 5-cm gap between the values for men and women [25], [28], [29].

Among Japanese in particular, the WC cutoff point is lower for men than for women, unlike the cutoff points proposed in other countries [9]. The visceral fat area has been noted as the golden standard for WC cutoff values for central obesity in Japanese. The WC value corresponding to a visceral fat area of 100cm2 and associated with a remarkable increase in the risk for cardiovascular disease is 85cm for men and 90cm for women [9]. In our study, we used the metabolic risk factors identified by the IDF as components of metabolic syndrome for the index in determining the WC cutoff points for central obesity.

A limitation of this study is its cross-sectional sample population; however, this was a representative sample of the general adult Korean population. Thus, these results can be generalized to the adult population of South Korea, aged 20–80 years, stratified by sex. Future studies prospectively relating the suggested WC cutoff points to the incidence of cardiovascular morbidity, cardiovascular mortality, and all-cause mortality in a representative sample of the adult Korean population are needed.

In conclusion, our analysis suggests that WC values of 90cm for men and 85cm for women are appropriate cutoff points for the designation of central obesity in Koreans. The high prevalence of metabolic risk factors among Koreans despite low WC values, as shown here, together with the increasing incidence of cardiovascular disease morbidity and mortality in South Korea underscore the importance of appropriate assessment of central obesity in screening for metabolic syndrome.

Acknowledgments

We thank the members of the Korea Institute for Health and Social Affairs, who conducted the national survey. HJY and HSP were involved in the conception and design of the study; SYL, DJK, SMK, JHH, and HSP performed data analysis; SRK, HSK, CBL, SJO, CYP, GJC, and DYK contributed to the interpretation of the data; SYL, DJK, and HSP drafted the manuscript.

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a Department of Family Medicine, College of Medicine, Pusan University, Pusan, Republic of Korea

b Department of Family Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea

c Department of Endocrinology and Metabolism, Ajou University School of Medicine, Suwon, Republic of Korea

d Department of Family Medicine, Eulji General Hospital, Eulji Medical University, Seoul, Republic of Korea

e Department of Family Medicine, College of Medicine, Korea University, Seoul, Republic of Korea

f Gurogu Public Health Center, Seoul, Republic of Korea

g Department of Family Medicine, Eastern Municipal Hospital, Seoul, Republic of Korea

h Department of Internal Medicine, College of Medicine, Catholic University of Korea, Seoul, Republic of Korea

i Department of Internal Medicine, College of Medicine, Hanyang University, Seoul, Republic of Korea

j Department of Endocrinology and Metabolism, School of Medicine, Kyung Hee University, Seoul, Republic of Korea

k Department of Internal Medicine, College of Medicine, Hallym University, Chunchon, Republic of Korea

Corresponding author at: Department of Family Medicine, University of Ulsan College of Medicine, 388-1 Poongnap-dong, Songpa-gu, Seoul 138-736, South Korea. Tel.: +82 2 3010 3813; fax: +82 2 3010 3815.

☆ This study was supported by a grant from the Korean Society for the Study of Obesity 2005.

PII: S0168-8227(06)00169-0

doi:10.1016/j.diabres.2006.04.013

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