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Appropriate waist circumference cutoff points for central obesity in Korean adults
Diabetes Research and Clinical Practice 75 (2007) 72–80 www.elsevier.com/locate/diabres
Appropriate waist circumference cutoff points for central obesity in Korean adults§ Sang Yeoup Lee a, Hye Soon Park b,*, Dae Jung Kim c, Jee Hye Han d, Seon Mee Kim e, Guem Joo Cho f, Dae Young Kim g, Hyuk Sang Kwon h, Sung Rae Kim h, Chang Beom Lee i, Seung Joon Oh j, Cheol Young Park k, Hyung Joon Yoo k b
a Department of Family Medicine, College of Medicine, Pusan University, Pusan, Republic of Korea 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
Received 9 March 2006; accepted 24 April 2006 Available online 2 June 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 85 cm for men and 80 cm for women. The odds ratio for the risk of two or more metabolic risk factors increased abruptly in men with WC 90 cm and women with WC 85 cm. The 80th percentile for WC in the Korean population was 90 cm for men and 86.5 cm for women. Thus, the appropriate WC cutoff point for central obesity in Koreans was determined to be 90 cm for men and 85 cm 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. # 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Obesity; Waist circumference; Cutoff points; Metabolic syndrome; Central obesity; Korean
§
This study was supported by a grant from the Korean Society for the Study of Obesity 2005. * 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. E-mail address: [email protected] (H.S. Park). 0168-8227/$ – see front matter # 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.diabres.2006.04.013
S.Y. Lee et al. / Diabetes Research and Clinical Practice 75 (2007) 72–80
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 102 cm for men and 88 cm for women [4], whereas, for Europeans, the cutoff was 94 cm for men and 80 cm 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 90 cm for men and 80 cm for women were adopted for South Asians and Chinese [8], and the Japanese used cutoff points of 85 cm for men and 90 cm for women [9]. Using the NCEP ATP III definition of central obesity [5] (men, >102 cm; women, >88 cm), 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, >90 cm; women, >80 cm), 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
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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 0.1 cm using a portable stadiometer (850– 2060 mm; Seriter, Bismarck, ND, USA). Weight was measured in the upright position to the nearest 0.1 kg 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 0.1 cm, 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 30 min 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
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by more than 5 mmHg, 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, 150 mg/dL (1.7 mmol/L); reduced HDL cholesterol, <40 mg/dL (<1.03 mmol/L) for men and <50 mg/dL (<1.29 mmol/L) for women; elevated blood pressure, systolic 130 mmHg, diastolic 85 mmHg, or treatment for previously diagnosed hypertension; elevated fasting plasma glucose, 100 mg/dL (5.6 mmol/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. Selfreported 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 30 g/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 genderspecific 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 falsepositive 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 <70 cm 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 23.2 kg/m2. The mean waist circumference was 82.8 cm in men and 78.6 cm 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 30 g of alcohol per day. 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,
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Table 1 Basic characteristics of the study population in the Korean National Health and Nutrition Examination Survey of 1998
a
Men (n = 2930)
Women (n = 3631)
Total (n = 6561)
Age (years) Body mass index (kg/m2)a Waist circumference (cm)a Education (%) 9 years 10–12 years >12 years
44.5 0.3 23.1 0.1 82.8 0.2
45.5 0.3 23.3 0.1 78.6 0.2
45.1 0.2 23.2 0.4 80.4 0.2
36.1 37.8 26.1
53.0 30.7 16.3
45.5 33.8 20.7
Smoking (%) Current smoker Ex-smoker Nonsmoker
65.5 17.2 17.3
6.7 2.5 90.8
32.8 9.0 58.2
Alcohol consumption (%) <10 g/day 10–30 g/day 30 g/day
50.1 28.2 21.7
92.9 6.0 1.1
73.9 15.8 10.3
Metabolic risk factors (%) Elevated triacylglycerol Reduced HDL cholesterol Elevated blood pressure Elevated fasting plasma glucose 2 risk factors
36.3 25.4 42.7 41.6 46.6
22.8 48.4 32.2 37.6 43.0
28.9 38.1 36.9 39.4 44.6
Metabolic risk factors were defined according to IDF criteria [2]. Elevated triacylglycerol, 150 mg/dL (1.7 mmol/L); reduced HDL cholesterol, <40 mg/dL (<1.03 mmol/L) for men and <50 mg/dL (<1.29 mmol/L) for women; elevated blood pressure: systolic blood pressure 130 mmHg, diastolic blood pressure 85 mmHg, or treatment for previously diagnosed hypertension; elevated fasting plasma glucose, 100 mg/dL (5.6 mmol/L) or previously diagnosed type 2 diabetes; and a combination of two or more of these metabolic risk factors. a The values are represented as means S.E.
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 95 cm (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 HDL cholesterol Systolic blood pressure Diastolic blood pressure Fasting plasma glucose
101.2 3.9 54.0 1.1 124.6 2.9 76.4 0.9 96.6 2.0
105.7 2.7 52.7 0.7 123.8 0.8 76.7 0.6 97.4 1.7
119.9 2.4 50.6 0.5 124.4 0.7 79.2 1.5 98.5 1.1
136.3 2.5 47.9 0.5 127.9 0.7 80.8 0.5 101.2 1.2
151.4 2.7 45.1 0.4 129.5 0.8 83.1 0.5 103.7 1.2
162.7 3.5 44.2 0.6 134.1 1.0 85.3 0.7 107.7 1.8
168.1 4.7 43.2 0.7 135.9 1.1 88.5 0.7 108.4 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 HDL cholesterol Systolic blood pressure Diastolic blood pressure Fasting plasma glucose
83.6 1.5 56.4 0.5 115.2 0.6 71.7 0.4 92.6 0.7
All values are means S.E.
98.2 1.9 53.3 0.5 117.7 0.7 74.3 0.9 95.2 1.0
109.5 2.0 51.2 0.5 124.4 1.0 76.4 0.8 99.7 1.3
127.2 2.3 48.7 0.5 127.1 0.8 78.3 0.5 103.2 1.4
134.6 2.8 48.3 0.6 131.9 1.0 80.5 0.5 106.9 1.9
139.9 3.9 48.5 0.8 137.1 1.5 82.0 0.8 113.7 2.5
148.2 3.7 47.1 0.8 138.6 1.5 83.2 0.8 112.1 2.7
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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
Men Elevated triacylglycerol Reduced HDL cholesterol Elevated blood pressure Elevated fasting plasma glucose 2 risk factors
Women Elevated triacylglycerol Reduced HDL cholesterol Elevated blood pressure Elevated fasting plasma glucose 2 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)
14.7 10.3 26.9 28.2 21.2
16.8 14.2 27.8 31.8 23.4
26.7 18.8 32.8 37.2 33.3
35.5 26.1 42.5 39.2 46.8
46.4 32.1 46.6 47.9 57.0
54.9 35.9 57.8 50.8 67.8
56.6 35.2 70.8 55.3 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)
7.1 30.4 13.3 22.5 15.8
13.9 41.3 19.0 28.5 27.8
19.4 48.0 30.4 37.2 40.7
31.2 59.1 37.6 42.2 56.2
32.9 59.7 49.2 51.9 63.8
42.0 60.9 59.2 55.9 71.8
50.0 65.4 63.9 56.3 77.4
Metabolic risk factors were defined according to IDF criteria [2]. Elevated triacylglycerol, 150 mg/dL (1.7 mmol/L); reduced HDL cholesterol, <40 mg/dL (<1.03 mmol/L) for men and <50 mg/dL (<1.29 mmol/L) for women; elevated blood pressure: systolic blood pressure 130 mmHg, diastolic blood pressure 85 mmHg, or treatment for previously diagnosed hypertension; elevated fasting plasma glucose, 100 mg/dL (5.6 mmol/L) or previously diagnosed type 2 diabetes; and a combination of two or more of these metabolic risk factors. All values are percentages (%).
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– 85 cm in men and about 75–80 cm in women. The 80th percentile for WC values was estimated as 90 cm in men and 86.5 cm in women. 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 5cm 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 90 cm and women with WC 85 cm. 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 90 cm for men and 85 cm for women as appropriate cutoff points for central obesity in Korean adults. These results are concordant with our previous study [17].
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)
Men 60 65 70 75 80 85 90 95 100
0.1 1.1 5.6 18.8 38.1 61.2 80.2 92.8 97.6
100.0 99.5 97.7 91.7 77.4 54.6 30.4 11.0 4.3
0.1 1.4 7.5 24.8 47.0 70.3 86.2 94.9 98.7
0.1 0.9 5.2 16.5 24.4 24.9 16.6 5.9 3.0
100.0 99.7 97.6 90.3 75.6 51.7 28.0 9.8 3.6
0.1 1.3 6.6 21.9 42.8 65.6 82.9 93.6 98.0
0.1 1.0 4.2 12.2 18.4 17.3 10.9 3.4 1.6
99.9 99.4 96.6 87.7 72.9 49.8 29.3 11.8 4.6
0.1 1.4 7.2 23.6 46.3 69.4 87.2 96.2 99.2
0.0 0.8 3.8 11.3 19.2 19.2 16.5 8.0 3.8
99.8 99.2 96.4 86.1 68.6 47.0 25.3 9.5 3.0
0.0 1.2 7.0 22.3 42.9 67.1 84.1 94.4 98.0
0.2 0.4 3.4 8.4 11.5 14.1 9.4 3.9 1.0
99.9 99.5 97.5 90.8 76.8 53.6 30.5 11.8 4.2
0.1 1.5 8.2 27.2 51.1 74.1 89.5 96.7 99.2
0.0 1.0 5.7 18.0 27.9 27.7 20.0 8.5 3.4
Women 60 65 70 75 80 85 90 95 100
0.6 6.1 20.4 39.8 58.5 75.5 87.9 94.5 97.7
99.9 98.7 93.7 81.4 65.7 42.5 24.2 11.9 5.1
0.8 7.5 24.6 46.1 65.7 80.8 91.4 96.4 98.6
0.7 6.2 18.3 27.5 31.4 23.3 15.6 8.3 3.7
99.7 96.4 87.3 70.6 51.9 31.3 15.8 7.5 3.3
0.9 8.4 27.5 49.6 68.3 81.8 91.3 96.3 98.7
0.6 4.7 14.8 20.2 20.2 13.1 7.1 3.8 2.0
99.7 97.8 91.5 79.9 62.2 42.6 23.1 10.9 4.3
0.7 7.9 26.0 49.2 68.4 84.0 93.1 97.0 98.7
0.4 5.7 17.5 29.1 30.6 26.6 16.2 7.9 3.0
99.3 96.1 87.9 73.0 54.4 35.2 18.2 8.4 3.4
0.6 7.4 25.4 47.5 66.3 81.9 91.5 96.2 98.4
0.1 3.5 13.3 20.5 20.7 17.1 9.7 4.6 1.8
99.7 98.0 92.6 79.7 62.0 39.8 21.0 9.9 3.9
0.9 9.2 30.2 54.5 74.0 87.0 94.5 97.7 99.0
0.6 7.2 22.8 34.2 36.0 26.8 15.5 7.6 2.9
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WC Percentile Elevated triacylglycerol Reduced HDL cholesterol Elevated blood pressure Elevated fasting glucose Two or more risk factors cutoff (cm) Sensitivity Specificity Yuden Sensitivity Specificity Yuden Sensitivity Specificity Yuden Sensitivity Specificity Yuden Sensitivity Specificity Yuden index index index index index
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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 < 70 cm 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.
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 5 cm 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 (>102 cm), European (94 cm), and Japanese men (85 cm), 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 (80 cm), 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 25 kg/m2 (WC: men, 94 cm; women, 80 cm) and 30 kg/m2 (WC: men, 102 cm; women, 88 cm) 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 102 cm 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: 90 cm for men and 83 cm for women at 25 kg/m2 BMI, and 100 cm for men and 93 cm for women at 30 kg/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 25 kg/m2, which is the cutoff for obesity in Asians, is about 90 cm for men and about 85 cm 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 [24–26]. The report of the joint WHO/IASO/IOTF committee proposed the WC values of 90 cm for men and 80 cm 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 10 cm greater than that for women. However, our study resulted in a cutoff value for men 5 cm greater than for women among Korean adults. A recent study in Chinese adults aged 35–74 years suggested the same WC value, 80 cm, 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 80–85 cm for men and 75–80 cm
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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 100 cm2 and associated with a remarkable increase in the risk for cardiovascular disease is 85 cm for men and 90 cm 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 90 cm for men and 85 cm 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. References [1] H.M. Lakka, D.E. Laaksonen, T.A. Lakka, L.K. Niskanen, E. Kumpusalo, J. Tuomilehto, et al., The metabolic syndrome and total and cardiovascular disease mortality in middle-aged men, JAMA 288 (2002) 2709–2716. [2] K.G. Alberti, P. Zimmet, J. Shaw, IDF Epidemiology Task Force Consensus Group. The metabolic syndrome—a new worldwide definition, Lancet 366 (2005) 1059–1062.
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[3] K.G. Alberti, P.Z. Zimmet, Definition, diagnosis and classification of diabetes mellitus and its complications. Part 1. Diagnosis and classification of diabetes mellitus provisional report of a WHO consultation, Diabet. Med. 15 (1998) 539–553. [4] Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Executive Summary of the Third Report of the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III). JAMA 285 (2001) 2486–2497. [5] B. Balkau, M.A. Charles, Comment on the provisional report from the WHO consultation. European Group for the Study of Insulin Resistance (EGIR), Diabet. Med. 16 (1999) 442–443. [6] P.M. McKeigue, B. Shah, M.G. Marmot, Relation of central obesity and insulin resistance with high diabetes prevalence and cardiovascular risk in South Asians, Lancet 337 (1991) 382–386. [7] M. Deurenberg-Yap, S.K. Chew, V.F. Lin, B.Y. Tan, W.A. van Staveren, P. Deurenberg, Relationships between indices of obesity and its co-morbidities in multi-ethnic Singapore, Int. J. Obes. Relat. Metab. Disord. 25 (2001) 1554–1562. [8] International Obesity Task Force. Asia–Pacific perspective: redefining obesity and its treatment. Western Pacific Region, Sydney, Australia, 2000. [9] Examination Committee of Criteria for ‘Obesity Disease’ in Japan; Japan Society for the Study of Obesity. New criteria for ‘obesity disease’ in Japan. Circ. J. 66 (2002) 987–992. [10] H.S. Park, S.W. Oh, S.I. Cho, W.H. Choi, Y.S. Kim, The metabolic syndrome and associated lifestyle factors among South Korean adults, Int. J. Epidemiol. 33 (2004) 328–336. [11] E.S. Ford, W.H. Giles, W.H. Dietz, Prevalence of the metabolic syndrome among US adults: findings from the third National Health and Nutrition Examination Survey, JAMA 287 (2002) 356–359. [12] H.S. Park, S.W. Oh, J.H. Kang, Y.W. Park, Y.S. Kim, W.H. Choi, et al., Prevalence and associated factors with metabolic syndrome in South Korea, J. Korean Soc. Study Obes. 12 (2003) 1– 14 (Korean). [13] American Society of Hypertension, Recommendations for routine blood pressure measurement by indirect cuff sphygmomanometry, Am. J. Hypertens. 5 (1992) 207–209. [14] B.J. Biggerstaff, Comparing diagnostic tests: a simple graphic using likelihood ratios, Stat. Med. 19 (2000) 649–663. [15] G.M. Reaven, Banting lecture 1988. Role of insulin resistance in human disease, Diabetes 37 (1988) 1595–1607. [16] Z.T. Bloomgarden, American Association of Clinical Endocrinologists (AACE) Consensus Conference on the Insulin Resistance Syndrome: August 25–26, 2002, Washington, DC, Diabet. Care 26 (2003) 1297–1303. [17] H.S. Park, Y.S. Yun, J.Y. Park, Y.S. Kim, J.M. Choi, Cut-off value of waist circumference for metabolic syndrome patients in Korean adult population, J. Korean Soc. Study Obes. 13 (2004) 53–60 (Korean). [18] M.E. Lean, T.S. Han, C.E. Morrison, Waist circumference as a measure for indicating need for weight management, BMJ 311 (1995) 158–161. [19] T.S. Han, E.M. van Leer, J.C. Seidell, M.E. Lean, Waist circumference action levels in the identification of cardiovascular risk factors: prevalence study in a random sample, BMJ 311 (1995) 1401–1405. [20] Y. Wang, E.B. Rimm, M.J. Stampfer, W.C. Willett, F.B. Hu, Comparison of abdominal adiposity and overall obesity in
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Appropriate waist circumference cutoff points for central obesity in Korean adults§ Sang Yeoup Lee a, Hye Soon Park b,*, Dae Jung Kim c, Jee Hye Han d, Seon Mee Kim e, Guem Joo Cho f, Dae Young Kim g, Hyuk Sang Kwon h, Sung Rae Kim h, Chang Beom Lee i, Seung Joon Oh j, Cheol Young Park k, Hyung Joon Yoo k b
a Department of Family Medicine, College of Medicine, Pusan University, Pusan, Republic of Korea 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
Received 9 March 2006; accepted 24 April 2006 Available online 2 June 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 85 cm for men and 80 cm for women. The odds ratio for the risk of two or more metabolic risk factors increased abruptly in men with WC 90 cm and women with WC 85 cm. The 80th percentile for WC in the Korean population was 90 cm for men and 86.5 cm for women. Thus, the appropriate WC cutoff point for central obesity in Koreans was determined to be 90 cm for men and 85 cm 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. # 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Obesity; Waist circumference; Cutoff points; Metabolic syndrome; Central obesity; Korean
§
This study was supported by a grant from the Korean Society for the Study of Obesity 2005. * 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. E-mail address: [email protected] (H.S. Park). 0168-8227/$ – see front matter # 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.diabres.2006.04.013
S.Y. Lee et al. / Diabetes Research and Clinical Practice 75 (2007) 72–80
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 102 cm for men and 88 cm for women [4], whereas, for Europeans, the cutoff was 94 cm for men and 80 cm 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 90 cm for men and 80 cm for women were adopted for South Asians and Chinese [8], and the Japanese used cutoff points of 85 cm for men and 90 cm for women [9]. Using the NCEP ATP III definition of central obesity [5] (men, >102 cm; women, >88 cm), 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, >90 cm; women, >80 cm), 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
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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 0.1 cm using a portable stadiometer (850– 2060 mm; Seriter, Bismarck, ND, USA). Weight was measured in the upright position to the nearest 0.1 kg 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 0.1 cm, 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 30 min 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
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by more than 5 mmHg, 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, 150 mg/dL (1.7 mmol/L); reduced HDL cholesterol, <40 mg/dL (<1.03 mmol/L) for men and <50 mg/dL (<1.29 mmol/L) for women; elevated blood pressure, systolic 130 mmHg, diastolic 85 mmHg, or treatment for previously diagnosed hypertension; elevated fasting plasma glucose, 100 mg/dL (5.6 mmol/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. Selfreported 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 30 g/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 genderspecific 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 falsepositive 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 <70 cm 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 23.2 kg/m2. The mean waist circumference was 82.8 cm in men and 78.6 cm 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 30 g of alcohol per day. 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,
S.Y. Lee et al. / Diabetes Research and Clinical Practice 75 (2007) 72–80
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Table 1 Basic characteristics of the study population in the Korean National Health and Nutrition Examination Survey of 1998
a
Men (n = 2930)
Women (n = 3631)
Total (n = 6561)
Age (years) Body mass index (kg/m2)a Waist circumference (cm)a Education (%) 9 years 10–12 years >12 years
44.5 0.3 23.1 0.1 82.8 0.2
45.5 0.3 23.3 0.1 78.6 0.2
45.1 0.2 23.2 0.4 80.4 0.2
36.1 37.8 26.1
53.0 30.7 16.3
45.5 33.8 20.7
Smoking (%) Current smoker Ex-smoker Nonsmoker
65.5 17.2 17.3
6.7 2.5 90.8
32.8 9.0 58.2
Alcohol consumption (%) <10 g/day 10–30 g/day 30 g/day
50.1 28.2 21.7
92.9 6.0 1.1
73.9 15.8 10.3
Metabolic risk factors (%) Elevated triacylglycerol Reduced HDL cholesterol Elevated blood pressure Elevated fasting plasma glucose 2 risk factors
36.3 25.4 42.7 41.6 46.6
22.8 48.4 32.2 37.6 43.0
28.9 38.1 36.9 39.4 44.6
Metabolic risk factors were defined according to IDF criteria [2]. Elevated triacylglycerol, 150 mg/dL (1.7 mmol/L); reduced HDL cholesterol, <40 mg/dL (<1.03 mmol/L) for men and <50 mg/dL (<1.29 mmol/L) for women; elevated blood pressure: systolic blood pressure 130 mmHg, diastolic blood pressure 85 mmHg, or treatment for previously diagnosed hypertension; elevated fasting plasma glucose, 100 mg/dL (5.6 mmol/L) or previously diagnosed type 2 diabetes; and a combination of two or more of these metabolic risk factors. a The values are represented as means S.E.
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 95 cm (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 HDL cholesterol Systolic blood pressure Diastolic blood pressure Fasting plasma glucose
101.2 3.9 54.0 1.1 124.6 2.9 76.4 0.9 96.6 2.0
105.7 2.7 52.7 0.7 123.8 0.8 76.7 0.6 97.4 1.7
119.9 2.4 50.6 0.5 124.4 0.7 79.2 1.5 98.5 1.1
136.3 2.5 47.9 0.5 127.9 0.7 80.8 0.5 101.2 1.2
151.4 2.7 45.1 0.4 129.5 0.8 83.1 0.5 103.7 1.2
162.7 3.5 44.2 0.6 134.1 1.0 85.3 0.7 107.7 1.8
168.1 4.7 43.2 0.7 135.9 1.1 88.5 0.7 108.4 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 HDL cholesterol Systolic blood pressure Diastolic blood pressure Fasting plasma glucose
83.6 1.5 56.4 0.5 115.2 0.6 71.7 0.4 92.6 0.7
All values are means S.E.
98.2 1.9 53.3 0.5 117.7 0.7 74.3 0.9 95.2 1.0
109.5 2.0 51.2 0.5 124.4 1.0 76.4 0.8 99.7 1.3
127.2 2.3 48.7 0.5 127.1 0.8 78.3 0.5 103.2 1.4
134.6 2.8 48.3 0.6 131.9 1.0 80.5 0.5 106.9 1.9
139.9 3.9 48.5 0.8 137.1 1.5 82.0 0.8 113.7 2.5
148.2 3.7 47.1 0.8 138.6 1.5 83.2 0.8 112.1 2.7
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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
Men Elevated triacylglycerol Reduced HDL cholesterol Elevated blood pressure Elevated fasting plasma glucose 2 risk factors
Women Elevated triacylglycerol Reduced HDL cholesterol Elevated blood pressure Elevated fasting plasma glucose 2 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)
14.7 10.3 26.9 28.2 21.2
16.8 14.2 27.8 31.8 23.4
26.7 18.8 32.8 37.2 33.3
35.5 26.1 42.5 39.2 46.8
46.4 32.1 46.6 47.9 57.0
54.9 35.9 57.8 50.8 67.8
56.6 35.2 70.8 55.3 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)
7.1 30.4 13.3 22.5 15.8
13.9 41.3 19.0 28.5 27.8
19.4 48.0 30.4 37.2 40.7
31.2 59.1 37.6 42.2 56.2
32.9 59.7 49.2 51.9 63.8
42.0 60.9 59.2 55.9 71.8
50.0 65.4 63.9 56.3 77.4
Metabolic risk factors were defined according to IDF criteria [2]. Elevated triacylglycerol, 150 mg/dL (1.7 mmol/L); reduced HDL cholesterol, <40 mg/dL (<1.03 mmol/L) for men and <50 mg/dL (<1.29 mmol/L) for women; elevated blood pressure: systolic blood pressure 130 mmHg, diastolic blood pressure 85 mmHg, or treatment for previously diagnosed hypertension; elevated fasting plasma glucose, 100 mg/dL (5.6 mmol/L) or previously diagnosed type 2 diabetes; and a combination of two or more of these metabolic risk factors. All values are percentages (%).
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– 85 cm in men and about 75–80 cm in women. The 80th percentile for WC values was estimated as 90 cm in men and 86.5 cm in women. 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 5cm 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 90 cm and women with WC 85 cm. 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 90 cm for men and 85 cm for women as appropriate cutoff points for central obesity in Korean adults. These results are concordant with our previous study [17].
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)
Men 60 65 70 75 80 85 90 95 100
0.1 1.1 5.6 18.8 38.1 61.2 80.2 92.8 97.6
100.0 99.5 97.7 91.7 77.4 54.6 30.4 11.0 4.3
0.1 1.4 7.5 24.8 47.0 70.3 86.2 94.9 98.7
0.1 0.9 5.2 16.5 24.4 24.9 16.6 5.9 3.0
100.0 99.7 97.6 90.3 75.6 51.7 28.0 9.8 3.6
0.1 1.3 6.6 21.9 42.8 65.6 82.9 93.6 98.0
0.1 1.0 4.2 12.2 18.4 17.3 10.9 3.4 1.6
99.9 99.4 96.6 87.7 72.9 49.8 29.3 11.8 4.6
0.1 1.4 7.2 23.6 46.3 69.4 87.2 96.2 99.2
0.0 0.8 3.8 11.3 19.2 19.2 16.5 8.0 3.8
99.8 99.2 96.4 86.1 68.6 47.0 25.3 9.5 3.0
0.0 1.2 7.0 22.3 42.9 67.1 84.1 94.4 98.0
0.2 0.4 3.4 8.4 11.5 14.1 9.4 3.9 1.0
99.9 99.5 97.5 90.8 76.8 53.6 30.5 11.8 4.2
0.1 1.5 8.2 27.2 51.1 74.1 89.5 96.7 99.2
0.0 1.0 5.7 18.0 27.9 27.7 20.0 8.5 3.4
Women 60 65 70 75 80 85 90 95 100
0.6 6.1 20.4 39.8 58.5 75.5 87.9 94.5 97.7
99.9 98.7 93.7 81.4 65.7 42.5 24.2 11.9 5.1
0.8 7.5 24.6 46.1 65.7 80.8 91.4 96.4 98.6
0.7 6.2 18.3 27.5 31.4 23.3 15.6 8.3 3.7
99.7 96.4 87.3 70.6 51.9 31.3 15.8 7.5 3.3
0.9 8.4 27.5 49.6 68.3 81.8 91.3 96.3 98.7
0.6 4.7 14.8 20.2 20.2 13.1 7.1 3.8 2.0
99.7 97.8 91.5 79.9 62.2 42.6 23.1 10.9 4.3
0.7 7.9 26.0 49.2 68.4 84.0 93.1 97.0 98.7
0.4 5.7 17.5 29.1 30.6 26.6 16.2 7.9 3.0
99.3 96.1 87.9 73.0 54.4 35.2 18.2 8.4 3.4
0.6 7.4 25.4 47.5 66.3 81.9 91.5 96.2 98.4
0.1 3.5 13.3 20.5 20.7 17.1 9.7 4.6 1.8
99.7 98.0 92.6 79.7 62.0 39.8 21.0 9.9 3.9
0.9 9.2 30.2 54.5 74.0 87.0 94.5 97.7 99.0
0.6 7.2 22.8 34.2 36.0 26.8 15.5 7.6 2.9
S.Y. Lee et al. / Diabetes Research and Clinical Practice 75 (2007) 72–80
WC Percentile Elevated triacylglycerol Reduced HDL cholesterol Elevated blood pressure Elevated fasting glucose Two or more risk factors cutoff (cm) Sensitivity Specificity Yuden Sensitivity Specificity Yuden Sensitivity Specificity Yuden Sensitivity Specificity Yuden Sensitivity Specificity Yuden index index index index index
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S.Y. Lee et al. / Diabetes Research and Clinical Practice 75 (2007) 72–80
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 < 70 cm 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.
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 5 cm 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 (>102 cm), European (94 cm), and Japanese men (85 cm), 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 (80 cm), 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 25 kg/m2 (WC: men, 94 cm; women, 80 cm) and 30 kg/m2 (WC: men, 102 cm; women, 88 cm) 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 102 cm 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: 90 cm for men and 83 cm for women at 25 kg/m2 BMI, and 100 cm for men and 93 cm for women at 30 kg/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 25 kg/m2, which is the cutoff for obesity in Asians, is about 90 cm for men and about 85 cm 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 [24–26]. The report of the joint WHO/IASO/IOTF committee proposed the WC values of 90 cm for men and 80 cm 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 10 cm greater than that for women. However, our study resulted in a cutoff value for men 5 cm greater than for women among Korean adults. A recent study in Chinese adults aged 35–74 years suggested the same WC value, 80 cm, 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 80–85 cm for men and 75–80 cm
S.Y. Lee et al. / Diabetes Research and Clinical Practice 75 (2007) 72–80
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 100 cm2 and associated with a remarkable increase in the risk for cardiovascular disease is 85 cm for men and 90 cm 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 90 cm for men and 85 cm 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. References [1] H.M. Lakka, D.E. Laaksonen, T.A. Lakka, L.K. Niskanen, E. Kumpusalo, J. Tuomilehto, et al., The metabolic syndrome and total and cardiovascular disease mortality in middle-aged men, JAMA 288 (2002) 2709–2716. [2] K.G. Alberti, P. Zimmet, J. Shaw, IDF Epidemiology Task Force Consensus Group. The metabolic syndrome—a new worldwide definition, Lancet 366 (2005) 1059–1062.
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