A Cross-Sectional Study of Socioeconomic Status and the Metabolic Syndrome in Korean Adults

A Cross-Sectional Study of Socioeconomic Status and the Metabolic Syndrome in Korean Adults MIN JUNG PARK, MD, KYUNG EUN YUN, MD, GO EUN LEE, MD, HONG JUN CHO, MD, AND HYE SOON PARK, MD

PURPOSE: Socioeconomic status may influence the risk of the metabolic syndrome. We investigated the association between socioeconomic status and the metabolic syndrome in Korean adults. METHODS: We analyzed a total of 8,541 subjects ages 20 to 79 years who participated in the Korean National Health and Nutrition Examination Survey, 2001. Socioeconomic status was measured by education and income level. RESULTS: The prevalence of the metabolic syndrome among this population was 29%. Relative to women with educational level !7 years, those with educational levels of 7 to 9 years, 10 to 12 years, and O13 years had odds ratios for the metabolic syndrome of 0.92 (95% confidence interval [CI]: 0.73 to 1.16), 0.55 (95% CI: 0.44 to 0.70), and 0.31 (95% CI: 0.22 to 0.43), respectively (p for trend !0.05). Relative to women with lower income, those with middle and upper income had odds ratios for the metabolic syndrome of 0.90 (95% CI: 0.75 to 1.08) and 0.80 (95% CI: 0.66 to 0.97), respectively (p for trend !0.05). A significant association between the metabolic syndrome and socioeconomic status was not observed in men. CONCLUSIONS: Lower socioeconomic status was associated with a higher risk of the metabolic syndrome in Korean women but not in Korean men. Ann Epidemiol 2007;17:320–326. Ó 2007 Elsevier Inc. All rights reserved. KEY WORDS:

Metabolic Syndrome, Socioeconomic Status, Korean.

INTRODUCTION The metabolic syndrome is associated with increased cardiovascular morbidity and mortality (1, 2). The Third Report of The National Cholesterol Education Program Adult Treatment Panel (NCEP ATP III) (3) has defined the metabolic syndrome as three or more of the five following criteria: high blood pressure (>130/>85 mm Hg), elevated fasting blood glucose (>110 mg/dL), hypertriglyceridemia (>150 mg/dL), low HDL-cholesterol (men, !40 mg/dL; women, !50 mg/dL), and abdominal obesity (waist circumference O102 cm for men and O88 cm for women). According to these criteria, the findings from the third National Health and Nutrition Examination Survey showed 24% of men and 23.7% of women in the United States have the metabolic syndrome (4), whereas in Korea, 14.2% of men and 17.7% of women have the metabolic syndrome in nationally representative samples (5). Using the AsiaPacific guideline for waist circumference (O90 cm for From the Department of Family Medicine, Asan Medical Center, University of Ulsan, College of Medicine, Seoul, Korea. Address correspondence to: Hye Soon Park, Department of Family Medicine, Asan Medical Center, University of Ulsan College of Medicine, 388-1, Poongnap-dong, Songpa-gu, Seoul, Korea 138-736. Tel.: 82-23010-3810; fax: 82-2-3010-3815. E-mail: [email protected]. Received May 30, 2006; accepted October 17, 2006. Ó 2007 Elsevier Inc. All rights reserved. 360 Park Avenue South, New York, NY 10010

men and O80cm for women) (6), the prevalence of the metabolic syndrome in Korea was 20.1% in men and 23.9% in women (7), similar to its prevalence in the United States. Socioeconomic status, as determined by the level of education and income (8), may influence the prevalence of the metabolic syndrome. In Western countries, individuals with lower-grade employment had a higher risk of the metabolic syndrome than those with higher-grade employment (9). Moreover, the metabolic syndrome has been found to be inversely proportional to household income (10) and education (11) as well as to be related to social relationships (12). In Korea, however, a positive association between education levels and mortality rates from ischemic heart disease has been observed (13). These findings indicate that in populations in developed countries, obesity and cardiovascular diseases occur more frequently among the poor, whereas the opposite occurs in less developed societies. In a previous study, we did not detect an association between income or education level and the metabolic syndrome (5). However, due to globalization and technological modernization, Korean society has been changing rapidly. We therefore investigated the relation between socioeconomic status and the metabolic syndrome in South Korean adults, using the latest national representative data. 1047-2797/07/$–see front matter doi:10.1016/j.annepidem.2006.10.007

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Selected Abbreviations and Acronyms NCEP ATP III Z The Third Report of the National Cholesterol Education Program Adult Treatment Panel KNHNES Z The Korean National Health and Nutrition Examination Survey

METHODS Study Population The 2001 Korean National Health and Nutrition Examination Survey (KNHNES) on Korean civilians, conducted by the Korean Ministry of Health and Welfare, used a stratified, multistage probability sampling design. Weights indicating the probability of being sampled were assigned to each respondent, enabling the results to represent the entire Korean population. The sampling frame was based on the 2000 National Census Registry. There were 246,097 primary sampling units, each of which contained about 60 households. Six hundred sampling frames, consisting of 13,200 households from the primary sampling units, were randomly sampled, and 12,183 households (92.3%) from these sampling frames were included. The Health Examination Study was completed by 9,770 (77.3%) of the 12,647 selected individuals taken Health Interview Survey. Blood tests were performed on 7,918 individuals over age 10 years, and data from 6,262 adults ages 20 to 79 years were included. We excluded 601 individuals (9.6%) who failed to fast overnight as well as 7 soldiers (0.1%) and 180 students (2.9%) who were unsuitable for social classification. Thus, our study included data from 5,474 individuals (87.4%). Since the survey used a stratified multistage probability sampling method, a weight variable was generated to back-calculate the original population distribution. Such use of weight allows unbiased point estimates of population parameters for the entire population and its subsets (14). This weighting of 5,474 observations resulted in 8,541 subjects who were representative of the census population. Health Interview Survey and Health Behavior Survey The Health Interview Survey and Health Behavior Survey included well-established questionnaires to determine the demographic and socioeconomic characteristics of the participants. Age was divided into six categories: 20 to 29, 30 to 39, 40 to 49, 50 to 59, 60 to 69, and 70 to 79 years. Marital status was categorized as married, unmarried, and others (divorced and widowed). Education level was categorized as less than 7 years (elementary school graduates), 7w9 years (middle school graduates), 10w12 years (high school graduates), and more than 13 years (college graduates). Monthly income was categorized as lower (!1,400 dollars), middle (1,400 to 2,500 dollars), and upper (O2,500 dollars),

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according to the tertile of monthly income (Korean nationwide average income: 1,850 dollars). Alcohol consumption was estimated from the usual daily intake of alcoholic beverages. The subjects were asked about their average frequency (days per week) and amount (in milliliters) of alcoholic beverages ingested on a typical occasion or during a typical day. The average amount and number of alcoholic beverages consumed was converted into the amount of pure alcohol (in grams) consumed per day. Subjects were divided into four groups by the amount of alcohol consumed: none, !15 g/day, 15 to 30 g/day, and >30 g/day. The participants were also classified as current smokers, exsmokers, and non-smokers. Those who were smoking at the time of the examination were defined as current smokers, and those who had smoked in the past but no longer smoked were defined as ex-smokers. Participants were divided into those who did and did not exercise regularly for more than 20 minutes per day during the previous month. Physical exercise was categorized as none, 4 times per week. Health Examination Study The Health Examination Study included anthropometric measurements and cardiovascular risk factors. Height was measured to the nearest 0.1 cm with the subject standing barefoot. Body weight was measured to the nearest 0.1 kg on a balanced scale while the subject wore a lightweight gown or underwear. Waist circumference was measured to the nearest 0.1 cm at the narrowest point between the lowest rib and the uppermost lateral border of the right iliac crest. Blood pressure was measured with a mercury sphygmomanometer (Baumanometer, WA Baum Co. Inc., New York, NY) after the subject had rested for 5 minutes in a sitting position. The first appearance of 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 (15). Two readings each of systolic and diastolic blood pressure were recorded, and the average of each measurement was used for data analysis. If the first two measurements differed by O5 mm Hg, additional readings were obtained. Blood samples were collected from the antecubital vein after overnight fasting. Fasting glucose, total cholesterol, triglycerides, and HDL cholesterol were measured by enzymatic methods with an autoanalyzer (Hitachi 747, Hitachi Instruments Inc., Tokyo, Japan). Definition of the Metabolic Syndrome We used the definition of the metabolic syndrome proposed by revised NCEP ATP III (16); the waist circumference cutoffs for abdominal obesity were those for Koreans (17). Thus, subjects satisfying three of these five criteria were

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classified as having the metabolic syndrome: waist measurement >90 cm for men and >85 cm for women; serum triglyceride concentration >150 mg/dL; HDL cholesterol !40 mg/dL for men and !50 mg/dL for women; fasting blood glucose >100 mg/dL; and systolic blood pressure >130 mm Hg or diastolic blood pressure >85 mm Hg. Subjects with a history of drug treatment for each of these components were assumed to have that component. Participants treated for hypertension were included in the high blood pressure group (8.2% of participants), whereas participants treated for type 2 diabetes were included in the high blood glucose group (2.6% of participants).

Statistical Analysis Sampling weights were used to take the complex sampling into account, and statistical analyses were conducted with the weighting using the statistical software, SAS version 8.1. Continuous variables were reported as mean G standard deviation. We described the data by stratification by sex because there was an interaction between sex and socioeconomic factors in association with the metabolic syndrome. The prevalence of the metabolic syndrome or each of its components was expressed in sex-specific proportions. The linear trend in the prevalence of the metabolic syndrome according to education and income was evaluated by using the c2 test for trend. Multiple logistic regression analysis was used to assess the association between education and income level and the metabolic syndrome. We determined which variables would be considered as confounders and included in multivariate-adjusted models. The adjusted odds ratios (OR) were presented together with their 95% confidence intervals (CI). Adjustments were carried out for those independent variables, including age, marital status, alcohol consumption, smoking status, exercise, and comorbid conditions. The linear trend in odds was evaluated by using the likelihood ratio test for trend. All analyses were two-tailed, and a value of p ! 0.05 was considered statistically significant.

RESULTS Basic Characteristics of the Study Population The basic characteristics of the study populations are shown in Table 1. The prevalence of the metabolic syndrome was 31.0% for men and 27.6% for women (Table 1). When abdominal obesity was defined as >102 cm for men and >88 cm for women, the prevalence of the metabolic syndrome was 23.2% for men and 24.8% for women.

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TABLE 1. Demographic characteristics of the study population (n Z 8541) Variable Age (20-79 years) Body mass index (kg/m2) Waist circumference (cm) Marital status Married Unmarried Others* Education level (years) !7 7–9 10–12 O12 Income level Lower Middle Upper Alcohol (g/day) None !15 15–30 O30 Smoking None Ex-smoker Current smoker Exercise (sessions/week) None <1 2–3 >4 Metabolic syndromey Yes No

Men (n Z 3657)

Women (n Z 4884)

Mean G SD

Mean G SD

45.5 G 17.7 23.7 G 3.9 84.5 G 10.1

45.0 G 18.4 23.4 G 4.3 78.6 G 12.0

No. (%) 2989 (81.7) 506 (13.8) 162 (4.4)

No. (%) 3612 (74.0) 461 (9.4) 810 (16.6)

581 (15.9) 478 (13.1) 1422 (38.9) 1175 (32.1)

1380 (28.3) 677 (13.9) 1789 (36.7) 1028 (21.1)

1237 (33.8) 1358 (37.1) 1063 (29.1)

1752 (35.9) 1635 (33.5) 1498 (30.7)

623 (17.0) 1730 (47.3) 617 (16.9) 688 (18.8)

1843 (37.7) 2816 (57.7) 150 (3.1) 76 (1.6)

649 (19.5) 669 (20.1) 2016 (60.5)

4259 (93.5) 65 (1.4) 233 (5.1)

2157 (64.9) 558 (16.8) 271 (8.1) 340 (10.2)

3454 (76.0) 435 (9.6) 305 (6.7) 353 (7.8)

1132 (31.0) 2525 (69.0)

1348 (27.6) 3536 (72.4)

*Including divorced, separated, and widowed. y Defined as having three or more of the five following criteria: abdominal obesity (waist circumference >90 cm for men, >85 cm for women), fasting plasma glucose >100 mg/dL, blood pressure >130/85 mm Hg, triglycerides >150 mg/dL, HDL cholesterol !40 mg/dL for men or !50 mg/dL for women.

Prevalence of the Metabolic Syndrome and Each Component According to Socioeconomic Status in Men and Women In men, there was no significant relation between the prevalence of the metabolic syndrome and education or income level. The prevalence of high blood glucose and high blood pressure showed significant inverse relations to education level in men, and the prevalence of high blood pressure showed a significant inverse relation to income level in men. However, the prevalence of abdominal obesity was significantly increased with income level in men. In women, the prevalence of the metabolic syndrome as well as each of its components showed significant inverse relations to education and income level (Tables 2 and 3).

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TABLE 2. Prevalence of the metabolic syndrome and each component according to socioeconomic status in men Variable

Metabolic syndrome No. (%)

Education level (years) !7 203 (35.0) 7–9 166 (34.7) 10–12 390 (27.4) O12 371 (31.6) Income level Lower 397 (32.1) Middle 361 (26.6) Upper 374 (35.2)

Abdominal obesity* No. (%)

High blood glucosey No. (%)

High blood pressurez No. (%)

High triglyceridesx No. (%)

Low HDL-cholesterolk No. (%)

134 (23.1) 115 (24.0) 328 (23.1) 306 (26.1)

263 (45.3) 219 (45.9) 559 (39.3) 433 (36.8){

330 (56.8) 221 (46.2) 552 (38.8) 411 (34.9){

243 (41.9) 206 (43.0) 601 (42.3) 504 (42.9)

244 (42.1) 207 (43.3) 496 (34.7) 483 (41.1)

255 (20.7) 325 (23.9) 302 (28.4){

506 (40.9) 526 (38.8) 445 (41.9)

593 (47.9) 504 (37.1) 419 (39.4){

528 (42.7) 545 (40.1) 481 (45.2)

490 (39.6) 486 (35.8) 456 (42.9)

*Abdominal obesity: waist circumference >90 cm. y Fasting blood glucose >100 mg/dL. z Blood pressure >130/85 mm Hg. x Triglycerides >150 mg/dL. k HDL-cholesterol !40 mg/dL. { p ! 0.05 from c2 test for trend.

Odds Ratios for the Metabolic Syndrome According to Socioeconomic Status in Men and Women In men, higher education (O12 years) and upper income level were significantly associated with higher odds ratio for the metabolic syndrome. However, these significances disappeared in the multivariate model. On the contrary, the odds ratios for the metabolic syndrome were significantly decreased as the education or income level increased in women (p ! 0.05 for trend). These significances remained after adjustment for covariables in the multivariate model in women (Tables 4, 5).

DISCUSSION The present study investigated the relation between socioeconomic status and the metabolic syndrome in Korean adults, using indexes for education and income. In men,

there was a higher age-adjusted odds ratio for the metabolic syndrome among those with higher education and income levels. However, we observed significant inverse relations between the prevalence of the metabolic syndrome as well as each component of the metabolic syndrome and education or income level in women. In particular, the odds ratios for the metabolic syndrome in women increased linearly as education or income level decreased, even in the multivariate model. The 2001 Korean National Health and Nutrition Examination Survey reported a higher prevalence of obese women among those with lower education and income levels (18). In men, however, there was a higher prevalence of obesity among those with higher education and income levels and among non-manual workers (18). Since obesity is an important risk factor for the metabolic syndrome, our findings are partially consistent with these results. Our findings may be due to specific aspects of Korean social culture. Women of

TABLE 3. Prevalence of the metabolic syndrome and each component according to socioeconomic status in women Variable

Metabolic syndrome No. (%)

Education level (years) !7 703 (50.9) 7–9 246 (36.3) 10–12 308 (17.2) O12 85 (8.3){ Income level Lower 688 (39.3) Middle 372 (22.7) Upper 288 (19.2){

Abdominal obesity* No. (%)

High blood glucosey No. (%)

High blood pressurez No. (%)

High triglyceridesx No. (%)

Low HDL-cholesterolk No. (%)

575 (41.7) 245 (36.2) 315 (17.6) 82 (8.0){

608 (44.1) 293 (43.3) 558 (31.2) 217 (21.2){

775(56.1) 268 (39.5) 293 (16.4) 97 (9.4){

530 (38.4) 212 (31.2) 373 (20.8) 137 (13.4){

998 (72.3) 416 (61.4) 1002 (56.0) 513 (49.9){

593 (33.8) 337 (20.6) 291 (19.4){

724 (41.4) 516 (31.6) 444 (29.6){

715 (40.8) 388 (23.8) 333 (22.2){

580(33.1) 378 (23.1) 298 (19.9){

1132 (64.6) 945 (57.8) 857 (57.2){

*Abdominal obesity: waist circumference >85 cm. y Fasting blood glucose >100 mg/dL. z Blood pressure >130/85 mm Hg. x Triglycerides >150 mg/dL. k HDL-cholesterol !50 mg/dL. { p ! 0.05 from c2 test for trend.

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TABLE 4. Odds ratios for the metabolic syndrome as a dependent variable and the associated factors as independent variables among Korean men

confounding and may explain why a significant association is seen among women but not men. The results of this study differ somewhat from those of our previous study, in which we used data from the 1998 Korean National Health and Nutrition Examination Survey (KNHNES) (5), perhaps because we used different criteria for the metabolic syndrome. In the earlier study, we used the original NCEP ATP III criteria for abdominal obesity (3), whereas in this study, we used the revised NCEP ATP III criteria (16). We repeated statistical analysis the present data, using the original NCEP ATP III definition to evaluate the difference of results according to different definitions. However, we found similar results, regardless of criteria of the metabolic syndrome. The reason for the discrepancy between these findings and the previous findings might be due to different characteristics of study populations. As Korean economy has grown rapidly, an inverse relation between socioeconomic status and the metabolic syndrome was shown in Korean women as in a developed society.

Categories Variables

OR* (95% CI) Age adjusted

Marital status Married 1.0 Unmarried 0.60 (0.46 – 0.78) Others 0.77 (0.55 – 1.09) Education level (years) !7 1.0 7-9 1.26 (0.97 – 1.64) 10-12 1.09 (0.86 – 1.38) O12 1.38 (1.09 – 1.76) Income level Lower 1.0 Middle 0.90 (0.76 – 1.07) Upper 1.30 (1.09 – 1.56) Alcohol (g/day) None 1.0 !15 0.94 (0.77 – 1.15) 15-30 1.26 (0.98 – 1.61) O30 1.26 (1.00 – 1.60) Smoking None 1.0 Ex-smoker 0.94 (0.76 – 1.17) Current smoker 0.89 (0.75 – 1.05) Exercise (sessions/week) None 1.0 <1 0.96 (0.78 – 1.18) 2-3 1.38 (1.06 – 1.80) >4 1.20 (0.94 – 1.52)

OR (95% CI) Multivariatey

p value

1.0 0.70 (0.52 – 0.96) 0.82 (0.57 – 1.17)

0.0263 0.2770

1.0 1.21 (0.91 – 1.59) 1.00 (0.78 – 1.29) 1.27 (0.98 – 1.66)

0.1856 0.9752 0.0763

1.0 0.82 (0.68 – 1.00) 1.09 (0.89 – 1.34)

0.0535 0.3867

1.0 0.93 (0.75 – 1.16) 1.26 (0.98 – 1.63) 1.26 (0.98 – 1.62)

0.5266 0.0773 0.0621

1.0 0.87 (0.69 – 1.09) 0.87 (0.75 – 1.08)

0.2312 0.2364

1.0 0.86 (0.69 – 1.07) 1.26 (0.95 – 1.66) 1.07 (0.83 – 1.39)

TABLE 5. Odds ratios for the metabolic syndrome as a dependent variable and the associated factors as independent variables among Korean women Categories Variables

0.1798 0.1075 0.5803

*OR denotes odds ratio. y Analyses were adjusted for age, marital status, alcohol, smoking, exercise, and comorbid conditions.

higher socioeconomic status tend to be more concerned about their health and fitness. They therefore tend to consume healthy food, engage in regular exercise, and check their physical condition periodically. In contrast, Korean men of higher socioeconomic status have a more sedentary lifestyle and many opportunities to consume richer foods and alcohol beverages but less opportunity to engage in physical labor. The discrepancy between Korean men and women may also be due to residual confounding by smoking. Only 4.7% of women reported being current smokers, compared with over 60% of men. There might be some misclassification in smoking status among women; for example, some women may not have reported that they were current smokers. There might be misclassification in smoking status among women so that attempting to remove confounding by smoking is inadequate, as some proportion of women do not accurately report that they are, in fact, current smokers. In that case, adjustment for smoking may result in residual

OR* (95% CI) Age adjusted

Marital status Married 1.0 Unmarried 0.41 (0.25 – 0.65) Others 1.05 (0.87 – 1.26) Education level (years) !7 1.0 7-9 0.99 (0.81 – 1.23) 10-12 0.55 (0.45 – 0.68) O12 0.29 (0.22 – 0.39)z Income level Lower 1.0 Middle 0.81 (0.69 – 0.96) Upper 0.62 (0.52 – 0.74)z Alcohol (g/day) None 1.0 !15 0.98 (0.84 – 1.14) 15-30 1.17 (0.76 – 1.80) O30 2.14 (1.28 – 3.58) Smoking None 1.0 Ex-smoker 0.64 (0.34 – 1.19) Current smoker 1.19 (0.88 – 1.62) Exercise (sessions/week) None 1.0 <1 0.94 (0.72 – 1.22) 2-3 0.77 (0.57 – 1.04) >4 1.13 (0.87 – 1.47)

OR (95% CI) Multivariatey

p value

1.0 0.49 (0.29 – 0.80) 1.03 (0.84 – 1.26)

0.0051 0.8069

1.0 0.92 (0.73 – 1.16) 0.55 (0.44 – 0.70) 0.31 (0.22 – 0.43)z

0.4901 !.0001 !.0001

1.0 0.90 (0.75 – 1.08) 0.80 (0.66 – 0.97)z

0.2599 0.0284

1.0 1.09 (0.93 – 1.28) 1.28 (0.82 – 2.00) 2.50 (1.47 – 4.26)

0.2706 0.2824 0.0007

1.0 0.60 (0.31 – 1.16) 1.11 (0.80 – 1.54)

0.1259 0.5185 0.7297

1.0 1.05 (0.79 – 1.39) 1.04 (0.76 – 1.43) 1.09 (0.83 – 1.45)

0.7297 0.8097 0.5375

*OR denotes odds ratio. y Analyses were adjusted for age, marital status, alcohol, smoking, exercise, and comorbid conditions. z p ! 0.05 from likelihood ratio test for trend.

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In the United States, low household income was associated with a higher risk for the metabolic syndrome (19). In France, the association between the metabolic syndrome and income was applicable to women but not to men (10). These studies also found that social class had a greater influence on the morbidity from chronic diseases in women than in men and that women’s health was more vulnerable to poverty and low socioeconomic status (20). A study on the relation between social class and obesity in Western developed countries also showed that obesity in women but not in men was more prevalent as socioeconomic status declined (21). The importance of education level in evaluating health may be due to the likelihood that higher education is accompanied by economically advantageous surroundings, as well as the opportunity to choose one’s health behaviors, solve problems, and handle diseases. It is also likely that more highly educated individuals are provided with greater levels of social, psychological, and economic support (22). Lower educational level is related to high morbidity and mortality from cardiovascular diseases, a relation clearer among women than men (23). In a Swedish study investigating the relation between educational level and the metabolic syndrome in healthy women (11), there were statistically significant associations between educational level and waist circumference, blood pressure, triglycerides, and HDL cholesterol. One possible explanation for these findings is that undesirable health behaviors are more prevalent in the less educated. Actually, smoking, drinking, and lack of exercise were more prevalent in women among lower socioeconomic status in our study. Household income has been found to be closely associated with low birth weight, poor cognitive development, infant and child mortality, adult mortality, and other markers of poor health (24). The association between low income and the higher risk of the metabolic syndrome may be associated with the limited resources available to low income people, which may induce them to choose low-cost, energy-dense food and to experience a lack of leisure activity and increased stress (10). Health-related behavior by itself, however, cannot explain the matter fully, and psychosocial stress must also be considered as a factor (25). Low socioeconomic status accompanied by psychosocial stress may induce a psychosocial defeat reaction with distinct physiological correlates, which would activate the hypothalamus-pituitary-adrenal axis and promote the development of risk factors (26). The Whitehall study of socioeconomic health inequality in the United Kingdom in 1991 (27) revealed inverse relations between socioeconomic status and disease morbidity and all-cause mortality. Thus, the increased risk of the metabolic syndrome in the lowest socioeconomic status may be due to bad health-related behaviors as well as to psychosocial stress

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from financial strain, job insecurity, low perceived control at work, stressful life events and poor social networks, depression, and low self-esteem (9). Although we could not analyze the associations between psychological stress and socioeconomic status in Korean adults, the psychosocial link may contribute to the significant relations between the metabolic syndrome and income and education levels in women. South Korea is in the transition period to a developed society, and the polarization of socioeconomic status may exacerbate health inequality and the chronic diseases associated with the metabolic syndrome. A major limitation of this study was its cross-sectional nature, which made it hard to judge causal relations. Another limitation was a possible misclassification of risk status. In particular, we could not exclude the misclassification of smoking status in women due to socially unacceptable norms of smoking among women. However, this study used representative national data, allowing us to infer an association between socioeconomic status and the metabolic syndrome among Korean adults. In conclusion, lower socioeconomic status was associated with a higher risk of the metabolic syndrome in Korean women but not in Korean men. To reduce the risk of the metabolic syndrome, a multidimensional effort by individuals, society, and the national health program is necessary. This study was supported by a grant of the Seoul R & BD Program, Republic of Korea (10526).

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