Abstract

Childhood obesity is directly related to cardiovascular disease (CVD) risk factors, but there is limited information on their relation in Korean children and adolescents. The authors investigated the association between obesity and CVD risk factors among 2,272 Korean boys and girls aged 10–18 years, who participated in the Korean National Health and Nutrition Examination Survey in 1998 and 2001. Obesity was defined by body mass index cutoff points provided by the US Centers for Disease Control and Prevention. The prevalence of obesity increased significantly from 5.4% in 1998 to 11.3% in 2001 (p < 0.0001). Korean obese children and adolescents in 1998 and 2001 had 4.6- and 4.9-fold risks for systolic hypertension, 4.2- and 2.8-fold risks for high levels of total cholesterol, 9.4- and 2.7-fold risks for high levels of low density lipoprotein cholesterol, 4.1- and 3.7-fold risks for low levels of high density lipoprotein cholesterol, and 5.3- and 2.8-fold risks for high levels of triglycerides, compared with their normal-weight counterparts (p < 0.05 in all). Approximately 60% of Korean obese children and adolescents had at least one CVD risk factor. These findings suggest that Korean obese children and adolescents have an increased risk of CVD.

The increasing prevalence of childhood obesity is a worldwide trend and is becoming a significant public health problem (1). Obesity in children and adolescents is associated with various cardiovascular disease (CVD) risk factors, including hypertension, dyslipidemia, and elevated insulin levels (24), as well as an increased risk of CVD morbidity and mortality in adulthood (5, 6). A decrease in physical activity and an increase in caloric intake may be responsible for this increasing incidence (7). Therefore, lifestyle modification and weight control aimed at both preventing and treating childhood obesity should reduce the risk of CVD in adulthood (2, 8).

Among Korean adults aged at least 20 years in 2001, 32.6 percent of males and 29.4 percent of females are obese, as defined by a body mass index of 25 or more kg/m2, and the prevalence of obese adults has increased (9). In addition, the mortality from CVD was one of the leading causes of death in 2003 in Korea (10). Strong linear relations between body mass index and hypertension, type 2 diabetes mellitus, dyslipidemia, ischemic heart disease, and stroke in Korean adults have been reported (1114). Obesity is a serious public health problem in Korean adults. However, little information is available regarding the association between obesity and CVD risk factors in Korean children and adolescents. The purpose of this study was to estimate the prevalence of hypertension, dyslipidemia, and elevated fasting glucose and to determine the association between obesity and CVD risk factors in Korean children and adolescents.

MATERIALS AND METHODS

Study population

This study was based on the data obtained from the Korean National Health and Nutrition Examination Survey (KNHANES) among noninstitutionalized civilians in the Republic of Korea (referred to as “South Korea”), which was conducted by the Korean Ministry of Health and Welfare in 1998 and 2001. This survey is a nationwide representative study using a stratified, multistage probability sampling design for the selection of household units. The participants completed three parts of a questionnaire belonging to the Health Interview Survey, the Health Behavior Survey, and the Nutrition Survey, and they underwent a Health Examination Survey. Subjects aged 10–18 years numbered 1,651 in 1998 and 1,158 in 2001. Subjects who did not fast for at least 8 hours or had one missing measurement were excluded. The final sample population for analysis consisted of 1,412 and 860 subjects in 1998 and 2001, respectively.

Health Examination Survey

Height was measured with a stadiometer, and body weight was measured on a balanced scale. Body mass index (weight (kg)/height (m)2) was calculated. Waist circumference was measured at the midpoint between the bottom of the rib cage and the top of the lateral border of iliac crest during minimal respiration. Blood pressure was measured by use of a mercury sphygmomanometer. Two measurements were made on all subjects at 5-minute intervals. The first and fifth Korotkoff sounds represented the systolic and diastolic blood pressure, respectively. The average of two measurements was used in data analysis.

Blood samples were collected in the morning after the subjects had fasted overnight and were analyzed in a national central laboratory. Serum total cholesterol, triglycerides, high density lipoprotein (HDL) cholesterol, and plasma fasting glucose were measured by use of enzymatic techniques. Low density lipoprotein (LDL) cholesterol was calculated by use of the Friedewald equation if the triglyceride measurement was less than 400 mg/dl (15).

Definition of overweight and CVD risk factors

Overweight status in childhood and adolescence was defined according to the body mass index cutoff points for age and gender proposed by the US Centers for Disease Control and Prevention (16). Subjects were classified as normal weight (<85th percentile), at risk of overweight (85th–<95th percentile), or overweight (≥95th percentile) according to the Korean growth charts (17). Hypertension was defined as a systolic blood pressure or a diastolic blood pressure greater than or equal to the 95th percentile for age, gender, and height (18, 19). A total cholesterol concentration of 200 mg/dl or more, a LDL cholesterol concentration of 130 mg/dl or more, and a triglyceride concentration of 130 mg/dl or more were defined as high (20). A low HDL cholesterol level and a high fasting glucose level were defined as a concentration of less than 35 mg/dl (21) and a concentration of 110 mg/dl or more, respectively.

Statistical analysis

The data were analyzed by use of SPSS software, version 11 for Windows (SPSS, Inc., Chicago, Illinois). Comparison of means of variables among the three groups stratified according to overweight status was done by analysis of variance with post hoc analysis (two sided). The chi-square test was used to examine differences in the prevalence of CVD risk factors between 1998 and 2001. The linear-by-linear association method was used for the trend test between overweight status and prevalence of CVD risk factors. Logistic regression analysis was used to examine the associations between overweight and CVD risk factors, and the referent was the normal-weight group. p < 0.05 was considered significant.

RESULTS

The prevalence of overweight boys increased significantly from 5.4 percent in 1998 to 11.6 percent in 2001 (p < 0.0001), while the prevalence of overweight girls increased significantly from 5.3 percent in 1998 to 10.9 percent in 2001 (p = 0.001) (figure 1). Characteristics of the subjects classified by overweight status were displayed in table 1 and table 2 on the basis of results from KNHANES 1998 and 2001, respectively. The overweight boys in 1998 had a significantly higher mean systolic blood pressure measurement; higher mean concentrations of total cholesterol, LDL cholesterol, and triglycerides; and a lower mean concentration of HDL cholesterol than did their normal-weight counterparts (in all: p < 0.0001). The overweight girls in 1998 had a significantly higher mean systolic blood pressure measurement (p = 0.001), higher mean concentrations of LDL cholesterol (p = 0.026) and triglycerides (p < 0.0001), and a lower mean concentration of HDL cholesterol (p < 0.0001) than did their normal-weight counterparts. The overweight boys in 2001 had a significantly higher mean systolic blood pressure measurement (p < 0.0001); higher mean concentrations of total cholesterol (p < 0.0001), LDL cholesterol (p = 0.001), and triglycerides (p < 0.0001); and a lower mean concentration of HDL cholesterol (p = 0.011) than did their normal-weight counterparts. The overweight girls in 2001 had a significantly higher mean systolic blood pressure measurement (p = 0.004); higher mean concentrations of total cholesterol (p = 0.002), LDL cholesterol (p = 0.004), and triglycerides (p < 0.0001); and a lower mean concentration of HDL cholesterol (p = 0.003) than did their normal-weight counterparts. In both 1998 and 2001, the mean diastolic blood pressure measurement and the mean concentrations of fasting glucose were not statistically different between the overweight and normal-weight subjects.

FIGURE 1.

Prevalence of overweight among boys and girls aged 10–18 years, Korean National Health and Nutrition Examination Survey, 1998 and 2001.

FIGURE 1.

Prevalence of overweight among boys and girls aged 10–18 years, Korean National Health and Nutrition Examination Survey, 1998 and 2001.

TABLE 1.

Characteristics (mean (standard deviation)) of 1,412 subjects aged 10–18 years according to overweight status, Korean National Health and Nutrition Examination Survey, 1998


Variable
 

Normal weight (622 boys, 554 girls)
 

At risk of overweight (74 boys, 86 girls)
 

Overweight (40 boys, 36 girls)
 

p value for difference (ANOVA*)
 
Age (years)     
    Boys 13.9 (2.5) 14.1 (2.7) 13.9 (3.0) 0.841 
    Girls 14.3 (2.6) 14.6 (2.6) 13.4 (2.8) 0.080 
Body mass index (kg/m2    
    Boys 18.8 (2.3) 24.3 (1.6) 27.8 (2.4) <0.0001 
    Girls 18.9 (2.2) 23.9 (1.4) 26.2 (1.8) <0.0001 
Systolic blood pressure (mmHg)     
    Boys 114.0 (11.2) 120.5 (11.6) 123.6 (10.9) <0.0001 
    Girls 111.3 (10.0) 114.1 (10.4) 116.4 (8.5) 0.001 
Diastolic blood pressure (mmHg)     
    Boys 65.0 (14.0) 66.9 (14.7) 70.1 (12.0) 0.056 
    Girls 66.0 (23.4) 65.8 (12.4) 68.0 (10.6) 0.860 
Total cholesterol (mg/dl)     
    Boys 154.1 (26.8) 160.9 (27.0) 176.6 (31.4) <0.0001 
    Girls 165.3 (28.6) 166.4 (27.8) 172.2 (38.3) 0.381 
LDL* cholesterol (mg/dl)     
    Boys 84.6 (21.8) 94.2 (23.3) 105.5 (29.3) <0.0001 
    Girls 93.0 (25.7) 98.0 (22.6) 103.2 (33.4) 0.026 
HDL* cholesterol (mg/dl)     
    Boys 54.0 (12.0) 46.6 (9.1) 47.6 (9.4) <0.0001 
    Girls 54.7 (11.5) 48.6 (11.0) 46.2 (10.1) <0.0001 
Triglycerides (mg/dl)     
    Boys 77.7 (41.2) 100.4 (41.5) 117.8 (51.1) <0.0001 
    Girls 88.6 (40.3) 100.0 (47.5) 114.2 (48.0) <0.0001 
Fasting glucose (mg/dl)     
    Boys 94.7 (12.5) 94.3 (12.1) 95.9 (13.5) 0.813 
    Girls
 
92.4 (11.9)
 
94.9 (12.4)
 
93.4 (10.2)
 
0.174
 

Variable
 

Normal weight (622 boys, 554 girls)
 

At risk of overweight (74 boys, 86 girls)
 

Overweight (40 boys, 36 girls)
 

p value for difference (ANOVA*)
 
Age (years)     
    Boys 13.9 (2.5) 14.1 (2.7) 13.9 (3.0) 0.841 
    Girls 14.3 (2.6) 14.6 (2.6) 13.4 (2.8) 0.080 
Body mass index (kg/m2    
    Boys 18.8 (2.3) 24.3 (1.6) 27.8 (2.4) <0.0001 
    Girls 18.9 (2.2) 23.9 (1.4) 26.2 (1.8) <0.0001 
Systolic blood pressure (mmHg)     
    Boys 114.0 (11.2) 120.5 (11.6) 123.6 (10.9) <0.0001 
    Girls 111.3 (10.0) 114.1 (10.4) 116.4 (8.5) 0.001 
Diastolic blood pressure (mmHg)     
    Boys 65.0 (14.0) 66.9 (14.7) 70.1 (12.0) 0.056 
    Girls 66.0 (23.4) 65.8 (12.4) 68.0 (10.6) 0.860 
Total cholesterol (mg/dl)     
    Boys 154.1 (26.8) 160.9 (27.0) 176.6 (31.4) <0.0001 
    Girls 165.3 (28.6) 166.4 (27.8) 172.2 (38.3) 0.381 
LDL* cholesterol (mg/dl)     
    Boys 84.6 (21.8) 94.2 (23.3) 105.5 (29.3) <0.0001 
    Girls 93.0 (25.7) 98.0 (22.6) 103.2 (33.4) 0.026 
HDL* cholesterol (mg/dl)     
    Boys 54.0 (12.0) 46.6 (9.1) 47.6 (9.4) <0.0001 
    Girls 54.7 (11.5) 48.6 (11.0) 46.2 (10.1) <0.0001 
Triglycerides (mg/dl)     
    Boys 77.7 (41.2) 100.4 (41.5) 117.8 (51.1) <0.0001 
    Girls 88.6 (40.3) 100.0 (47.5) 114.2 (48.0) <0.0001 
Fasting glucose (mg/dl)     
    Boys 94.7 (12.5) 94.3 (12.1) 95.9 (13.5) 0.813 
    Girls
 
92.4 (11.9)
 
94.9 (12.4)
 
93.4 (10.2)
 
0.174
 
*

ANOVA, analysis of variance; LDL, low density lipoprotein; HDL, high density lipoprotein.

TABLE 2.

Characteristics (mean (standard deviation)) of 860 subjects aged 10–18 years according to overweight status, Korean National Health and Nutrition Examination Survey, 2001


Variable
 

Normal weight (346 boys, 313 girls)
 

At risk of overweight (58 boys, 46 girls)
 

Overweight (53 boys, 44 girls)
 

p value for difference (ANOVA*)
 
Age (years)     
    Boys 13.6 (2.4) 13.7 (2.3) 13.3 (2.7) 0.623 
    Girls 13.9 (2.4) 14.4 (2.7) 12.6 (2.5) 0.001 
Body mass index (kg/m2    
    Boys 19.1 (2.2) 24.5 (1.6) 28.0 (3.2) <0.0001 
    Girls 19.1 (2.2) 23.6 (1.6) 25.6 (2.5) <0.0001 
Systolic blood pressure (mmHg)     
    Boys 111.8 (11.5) 116.6 (10.5) 120.0 (11.0) <0.0001 
    Girls 106.1 (10.0) 107.5 (10.2) 111.5 (11.0) 0.004 
Diastolic blood pressure (mmHg)     
    Boys 64.5 (11.9) 66.7 (10.7) 68.1 (12.2) 0.065 
    Girls 63.7 (10.0) 63.8 (10.4) 64.1 (10.6) 0.971 
Total cholesterol (mg/dl)     
    Boys 155.4 (26.4) 171.0 (23.9) 169.7 (30.9) <0.0001 
    Girls 165.6 (25.5) 172.9 (29.4) 179.1 (24.8) 0.002 
LDL* cholesterol (mg/dl)     
    Boys 91.1 (22.3) 100.4 (23.2) 101.0 (26.6) 0.001 
    Girls 97.1 (22.2) 104.6 (24.3) 107.5 (21.9) 0.004 
HDL* cholesterol (mg/dl)     
    Boys 46.5 (9.6) 45.5 (8.4) 42.2 (8.4) 0.011 
    Girls 50.2 (9.5) 47.0 (8.4) 45.8 (9.5) 0.003 
Triglycerides (mg/dl)     
    Boys 89.7 (46.7) 125.4 (84.4) 138.5 (93.4) <0.0001 
    Girls 91.4 (42.8) 106.7 (56.8) 129.3 (71.0) <0.0001 
Fasting glucose (mg/dl)     
    Boys 94.6 (12.1) 95.6 (10.5) 97.7 (11.6) 0.183 
    Girls
 
93.6 (11.8)
 
92.0 (12.1)
 
93.7 (8.7)
 
0.668
 

Variable
 

Normal weight (346 boys, 313 girls)
 

At risk of overweight (58 boys, 46 girls)
 

Overweight (53 boys, 44 girls)
 

p value for difference (ANOVA*)
 
Age (years)     
    Boys 13.6 (2.4) 13.7 (2.3) 13.3 (2.7) 0.623 
    Girls 13.9 (2.4) 14.4 (2.7) 12.6 (2.5) 0.001 
Body mass index (kg/m2    
    Boys 19.1 (2.2) 24.5 (1.6) 28.0 (3.2) <0.0001 
    Girls 19.1 (2.2) 23.6 (1.6) 25.6 (2.5) <0.0001 
Systolic blood pressure (mmHg)     
    Boys 111.8 (11.5) 116.6 (10.5) 120.0 (11.0) <0.0001 
    Girls 106.1 (10.0) 107.5 (10.2) 111.5 (11.0) 0.004 
Diastolic blood pressure (mmHg)     
    Boys 64.5 (11.9) 66.7 (10.7) 68.1 (12.2) 0.065 
    Girls 63.7 (10.0) 63.8 (10.4) 64.1 (10.6) 0.971 
Total cholesterol (mg/dl)     
    Boys 155.4 (26.4) 171.0 (23.9) 169.7 (30.9) <0.0001 
    Girls 165.6 (25.5) 172.9 (29.4) 179.1 (24.8) 0.002 
LDL* cholesterol (mg/dl)     
    Boys 91.1 (22.3) 100.4 (23.2) 101.0 (26.6) 0.001 
    Girls 97.1 (22.2) 104.6 (24.3) 107.5 (21.9) 0.004 
HDL* cholesterol (mg/dl)     
    Boys 46.5 (9.6) 45.5 (8.4) 42.2 (8.4) 0.011 
    Girls 50.2 (9.5) 47.0 (8.4) 45.8 (9.5) 0.003 
Triglycerides (mg/dl)     
    Boys 89.7 (46.7) 125.4 (84.4) 138.5 (93.4) <0.0001 
    Girls 91.4 (42.8) 106.7 (56.8) 129.3 (71.0) <0.0001 
Fasting glucose (mg/dl)     
    Boys 94.6 (12.1) 95.6 (10.5) 97.7 (11.6) 0.183 
    Girls
 
93.6 (11.8)
 
92.0 (12.1)
 
93.7 (8.7)
 
0.668
 
*

ANOVA, analysis of variance; LDL, low density lipoprotein; HDL, high density lipoprotein.

The prevalence changes of CVD risk factors from 1998 to 2001 were given in table 3. For boys, the prevalence of high LDL cholesterol, low HDL cholesterol, and high triglycerides significantly increased from 1998 to 2001 (p = 0.029, p < 0.001, and p < 0.001, respectively).

TABLE 3.

Prevalence of cardiovascular disease risk factors among subjects aged 10–18 years, Korean National Health and Nutrition Examination Survey, 1998 and 2001


Cardiovascular disease risk factors
 

KNHANES,* 1998 (736 boys, 676 girls)
 
 
KNHANES, 2001 (457 boys, 403 girls)
 
 
p value for difference
 
 No.
 
%
 
No.
 
%
 
 
Systolic hypertension      
    Boys 83 11.3 43 9.4 0.307 
    Girls 66 9.8 23 5.7 0.019 
Diastolic hypertension      
    Boys 46 6.3 19 4.2 0.122 
    Girls 42 6.2 10 2.5 0.006 
High total cholesterol      
    Boys 49 6.7 36 7.9 0.421 
    Girls 71 10.5 45 11.2 0.734 
High LDL* cholesterol      
    Boys 33 4.5 34 7.5 0.029 
    Girls 52 7.7 36 8.9 0.091 
Low HDL* cholesterol      
    Boys 24 3.3 38 8.3 <0.001 
    Girls 25 3.7 17 4.2 0.476 
High triglycerides      
    Boys 81 11.0 88 19.3 <0.001 
    Girls 107 15.8 80 19.9 0.669 
High fasting glucose      
    Boys 66 9.0 42 9.2 0.896 
    Girls
 
50
 
7.4
 
24
 
6.0
 
0.365
 

Cardiovascular disease risk factors
 

KNHANES,* 1998 (736 boys, 676 girls)
 
 
KNHANES, 2001 (457 boys, 403 girls)
 
 
p value for difference
 
 No.
 
%
 
No.
 
%
 
 
Systolic hypertension      
    Boys 83 11.3 43 9.4 0.307 
    Girls 66 9.8 23 5.7 0.019 
Diastolic hypertension      
    Boys 46 6.3 19 4.2 0.122 
    Girls 42 6.2 10 2.5 0.006 
High total cholesterol      
    Boys 49 6.7 36 7.9 0.421 
    Girls 71 10.5 45 11.2 0.734 
High LDL* cholesterol      
    Boys 33 4.5 34 7.5 0.029 
    Girls 52 7.7 36 8.9 0.091 
Low HDL* cholesterol      
    Boys 24 3.3 38 8.3 <0.001 
    Girls 25 3.7 17 4.2 0.476 
High triglycerides      
    Boys 81 11.0 88 19.3 <0.001 
    Girls 107 15.8 80 19.9 0.669 
High fasting glucose      
    Boys 66 9.0 42 9.2 0.896 
    Girls
 
50
 
7.4
 
24
 
6.0
 
0.365
 
*

KNHANES, Korean National Health and Nutrition Examination Survey; LDL, low density lipoprotein; HDL, high density lipoprotein.

Chi-square test.

The prevalence of systolic hypertension, high total cholesterol, high LDL cholesterol, low HDL cholesterol, and high triglycerides increased in a graded fashion from the normal-weight group to the overweight group in both 1998 and 2001 (in all: ptrend < 0.05) (table 4). The age- and gender-adjusted odds ratios for systolic hypertension, high total cholesterol, high LDL cholesterol, low HDL cholesterol, and high triglycerides were highest in the overweight group in both 1998 and 2001 (table 4). In 1998, the overweight children and adolescents showed a strong association with systolic hypertension, diastolic hypertension, high total cholesterol, high LDL cholesterol, low HDL cholesterol, and high triglycerides (age- and gender-adjusted odds ratio = 4.55, 2.65, 4.15, 9.42, 4.10, and 5.30, respectively). In 2001, the overweight children and adolescents showed a strong association with systolic hypertension, high total cholesterol, high LDL cholesterol, low HDL cholesterol, and high triglycerides (age- and gender-adjusted odds ratio = 4.94, 2.78, 2.67, 3.64, and 2.77, respectively).

TABLE 4.

Prevalence and age- and gender-adjusted odds ratios for cardiovascular disease risk factors in subjects aged 10–18 years, Korean National Health and Nutrition Examination Survey, 1998 and 2001


Cardiovascular disease risk factors
 

Normal weight, prevalence (%)
 

At risk of overweight
 
  
Overweight
 
  
  Prevalence (%)
 
Odds ratio
 
95% confidence interval
 
Prevalence (%)
 
Odds ratio
 
95% confidence interval
 
Systolic hypertension        
    1998 9.1 20.0 2.95 1.89, 4.59 28.9* 4.55 2.65, 7.81 
    2001 5.2 9.6 2.01 0.95, 4.24 22.7* 4.94 2.72, 8.97 
Diastolic hypertension        
    1998 5.4 8.8 1.66 0.91, 3.03 13.2* 2.65 1.30, 5.41 
    2001 3.2 3.8 1.18 0.40, 3.51 4.1 1.35 0.45, 4.04 
High total cholesterol        
    1998 7.1 11.3 1.58 0.92, 2.71 23.7* 4.15 2.33, 7.40 
    2001 7.3 14.4 2.23 1.20, 4.17 18.6* 2.78 1.53, 5.05 
High LDL cholesterol        
    1998 4.3 8.1 1.81 0.96, 3.43 27.6* 9.42 5.21, 17.04 
    2001 6.5 11.5 1.88 0.96, 3.71 15.8* 2.67 1.41, 5.05 
Low HDL cholesterol        
    1998 2.5 8.1 3.43 1.74, 6.75 9.2* 4.10 1.73, 9.71 
    2001 4.9 8.7 1.77 0.81, 3.85 14.4* 3.64 1.84, 7.21 
High triglycerides        
    1998 10.4 23.1 2.58 1.70, 3.91 38.2* 5.30 3.20, 8.77 
    2001 15.6 29.8 2.35 1.47, 3.77 35.1* 2.77 1.73, 4.44 
High fasting glucose        
    1998 8.2 9.4 1.18 0.67, 2.10 5.3 0.61 0.22, 1.69 
    2001
 
7.7
 
5.8
 
0.74
 
0.31, 1.78
 
9.3
 
1.10
 
0.52, 2.32
 

Cardiovascular disease risk factors
 

Normal weight, prevalence (%)
 

At risk of overweight
 
  
Overweight
 
  
  Prevalence (%)
 
Odds ratio
 
95% confidence interval
 
Prevalence (%)
 
Odds ratio
 
95% confidence interval
 
Systolic hypertension        
    1998 9.1 20.0 2.95 1.89, 4.59 28.9* 4.55 2.65, 7.81 
    2001 5.2 9.6 2.01 0.95, 4.24 22.7* 4.94 2.72, 8.97 
Diastolic hypertension        
    1998 5.4 8.8 1.66 0.91, 3.03 13.2* 2.65 1.30, 5.41 
    2001 3.2 3.8 1.18 0.40, 3.51 4.1 1.35 0.45, 4.04 
High total cholesterol        
    1998 7.1 11.3 1.58 0.92, 2.71 23.7* 4.15 2.33, 7.40 
    2001 7.3 14.4 2.23 1.20, 4.17 18.6* 2.78 1.53, 5.05 
High LDL cholesterol        
    1998 4.3 8.1 1.81 0.96, 3.43 27.6* 9.42 5.21, 17.04 
    2001 6.5 11.5 1.88 0.96, 3.71 15.8* 2.67 1.41, 5.05 
Low HDL cholesterol        
    1998 2.5 8.1 3.43 1.74, 6.75 9.2* 4.10 1.73, 9.71 
    2001 4.9 8.7 1.77 0.81, 3.85 14.4* 3.64 1.84, 7.21 
High triglycerides        
    1998 10.4 23.1 2.58 1.70, 3.91 38.2* 5.30 3.20, 8.77 
    2001 15.6 29.8 2.35 1.47, 3.77 35.1* 2.77 1.73, 4.44 
High fasting glucose        
    1998 8.2 9.4 1.18 0.67, 2.10 5.3 0.61 0.22, 1.69 
    2001
 
7.7
 
5.8
 
0.74
 
0.31, 1.78
 
9.3
 
1.10
 
0.52, 2.32
 
*

p < 0.05 (trend in prevalence according to overweight status using linear-by-linear association).

LDL, low density lipoprotein; HDL, high density lipoprotein.

The clustering of CVD risk factors was shown in Korean obese children and adolescents (table 5). Among the overweight subjects, 65.8 percent in 1998 and 63.2 percent in 2001 had at least one of the significant five CVD risk factors, while 24.3 percent in 1998 and 28.6 percent in 2001 among normal-weight subjects had at least one significant CVD risk factor.

TABLE 5.

Prevalence of clustering of cardiovascular disease risk factors according to overweight status among subjects aged 10–18 years, Korean National Health and Nutrition Examination Survey, 1998 and 2001


No. of significant risk factors*
 

Normal weight
 
 
At risk of overweight
 
 
Overweight
 
 
 No.
 
%
 
No.
 
%
 
No.
 
%
 
      
    1998 889 75.7 88 55.0 26 34.2 
    2001 470 71.4 56 53.8 35 36.8 
≥1       
    1998 286 24.3 72 45.0 50 65.8 
    2001 188 28.6 48 46.2 60 63.2 
≥2       
    1998 72 6.1 29 18.1 29 38.2 
    2001 61 9.3 25 24.0 25 26.3 
≥3       
    1998 20 1.7 11 6.9 13 17.1 
    2001
 
9
 
1.4
 
4
 
3.8
 
9
 
9.5
 

No. of significant risk factors*
 

Normal weight
 
 
At risk of overweight
 
 
Overweight
 
 
 No.
 
%
 
No.
 
%
 
No.
 
%
 
      
    1998 889 75.7 88 55.0 26 34.2 
    2001 470 71.4 56 53.8 35 36.8 
≥1       
    1998 286 24.3 72 45.0 50 65.8 
    2001 188 28.6 48 46.2 60 63.2 
≥2       
    1998 72 6.1 29 18.1 29 38.2 
    2001 61 9.3 25 24.0 25 26.3 
≥3       
    1998 20 1.7 11 6.9 13 17.1 
    2001
 
9
 
1.4
 
4
 
3.8
 
9
 
9.5
 
*

Significant cardiovascular disease risk factors: systolic hypertension; high levels of triglycerides and low density lipoprotein cholesterol; and low levels of high density lipoprotein cholesterol.

DISCUSSION

The present study demonstrated that Korean overweight children and adolescents aged 10–18 years had more elevated blood pressure, more adverse lipid levels, and more clustered numbers of CVD risk factors than did normal-weight counterparts. In addition, a significant increase of overweight during a short period was observed. These findings were consistent with the data reported in other studies (2, 2224). However, caution should be taken when comparing the data with other results, because different definitions for overweight status and CVD risk factors are used. Herein, overweight was used interchangeably with obesity, similar to a majority of US studies (2, 17, 22).

Elevated blood pressure is more frequently present in overweight children than in nonoverweight children (25). The present study showed a similar finding on systolic blood pressure, but there was no significant association between overweight and diastolic blood pressure in 2001. In the Bogalusa Heart Study, overweight schoolchildren (body mass index: ≥95th percentile) have 2.4-fold risk of diastolic hypertension (2). In a German study, the degree of body mass index correlates positively with diastolic hypertension (24). The decreasing prevalence of diastolic hypertension from 1998 to 2001, as well as the smaller size of sample population in 2001 than in 1998, might be one reason for a different finding on diastolic hypertension.

Overweight is strongly related to concentrations of HDL cholesterol and triglycerides and weakly related to concentrations of total and LDL cholesterol (2). In a German study, total and LDL cholesterol concentrations did not correlate significantly with the degree of overweight (24). In the present study, all types of lipids were significantly associated with overweight.

In contrast to blood pressure and lipid profiles, fasting glucose concentrations did not increase according to the increase in overweight status. However, in the Taipei Children Heart Study, a significant correlation between obesity (body mass index: ≥85th percentile) and high fasting glucose (≥90th percentile) is reported (23). The small number of overweight subjects and very low prevalence of high fasting glucose made these findings statistically insignificant.

The fasting plasma insulin level is a proper measure of insulin resistance and has a significant relation with obesity and CVD (4, 26). In the Young Finns Study (27), the serum insulin concentration correlates positively with body mass index. In the Bogalusa Heart Study, overweight schoolchildren were found to have a 2.4-fold risk for high fasting plasma insulin (2). However, fasting plasma insulin was not measured in the Health Examination Survey of KNHANES. The relation between fasting plasma insulin and overweight is suggested indirectly through another Korean study where the mean concentration of fasting plasma insulin is significantly higher in overweight children than in normal-weight controls (28).

There were two limitations in the present study. First, because there are no formal cutoff points of blood pressure for age, gender, and height to define hypertension for Korean children and adolescents, the present study used US cutoff points after stratifying them into Korean height percentiles (16, 18). This was based on the assumption that there is no significant difference in blood pressure among ethnic groups during childhood and adolescence (29). Fortunately, the present study showed a significant association between systolic hypertension and overweight, which was consistent with results from other studies (2, 23, 24). The second limitation is that these results might not be representative of Korean children and adolescents. Although KNHANES used a stratified and multistage probability sampling design to estimate the representative indices in Koreans, the population distribution of the present study was slightly different from that of the original subjects in KNHANES because of the exclusion of subjects with missing values on the variables for logistic regression testing.

In summary, the numbers of overweight Korean children and adolescents have increased rapidly, and they have an increased risk of elevated blood pressure; high concentrations of total cholesterol, LDL cholesterol, and triglycerides; and a low concentration of HDL cholesterol. These findings suggest that overweight Korean children and adolescents might have an increased risk of CVD morbidity and mortality in adulthood.

Conflict of interest: none declared.

References

1.
Ebbeling CA, Pawlak DB, Ludwig DS. Childhood obesity: public-health crisis, common sense cure.
Lancet
 
2002
;
360
:
473
–82.
2.
Freedman DS, Dietz WH, Srinivasan SR, et al. The relation of overweight to cardiovascular risk factors among children and adolescents: the Bogalusa Heart Study.
Pediatrics
 
1999
;
103
:
1175
–82.
3.
Berenson GS, Srinivasan SR, Bao W, et al. Association between multiple cardiovascular risk factors and atherosclerosis in children and young adults.
N Eng J Med
 
1998
;
338
:
1650
–6.
4.
Bao W, Srinivasan SR, Berenson GS. Persistent elevation of plasma insulin levels is associated with increased cardiovascular risk in children and young adults. The Bogalusa Heart Study.
Circulation
 
1996
;
93
:
54
–9.
5.
Must A, Jacques PF, Dallal GE, et al. Long term morbidity and mortality of overweight adolescents: a follow-up of the Harvard Growth Study of 1922 to 1935.
N Eng J Med
 
1992
;
327
:
1350
–5.
6.
Gunnell DJ, Frankel SJ, Nanchahal K, et al. Childhood obesity and adult cardiovascular mortality: a 57-y follow-up study based on the Boyd Orr cohort.
Am J Clin Nutr
 
1998
;
67
:
1111
–18.
7.
Miller J, Rosenbloom A, Silverstein J. Childhood obesity.
J Clin Endocrinol Metab
 
2004
;
89
:
4211
–18.
8.
Haffner SM, Valdez RA, Hazuda HP, et al. Prospective analysis of the insulin-resistance syndrome (syndrome X).
Diabetes
 
1992
;
41
:
715
–22.
9.
Kim DM, Ahn CW, Nam SY. Prevalence of obesity in Korea.
Obes Rev
 
2005
;
6
:
117
–21.
10.
Korea National Statistical Office. 2003 report of statistics of mortality in Koreans. (In Korean). Daejeon, Republic of Korea: Korea National Statistical Office,
2004
.
11.
Moon OR, Kim NS, Jang SM, et al. The relationship between body mass index and the prevalence of obesity-related diseases based on the 1995 National Health Interview Survey in Korea.
Obes Rev
 
2002
;
3
:
191
–6.
12.
Park HS, Yun YS, Park JY, et al. Obesity, abdominal obesity, and clustering of cardiovascular risk factors in South Korea.
Asia Pac J Clin Nutr
 
2003
;
12
:
411
–18.
13.
Jee SH, Pastor-Barriuso R, Appel LJ, et al. Body mass index and incident ischemic heart disease in South Korean men and women.
Am J Epidemiol
 
2005
;
162
:
42
–8.
14.
Song YM, Sung JH, Smith GD, et al. Body mass index and ischemic and hemorrhagic stroke. A prospective study in Korean men.
Stroke
 
2004
;
35
:
831
–6.
15.
Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge.
Clin Chem
 
1972
;
18
:
499
–502.
16.
Himes JH, Dietz WH. Guidelines for overweight in adolescent preventive services: recommendations from an expert committee. The Expert Committee on Clinical Guidelines for Overweight in Adolescent Preventive Services.
Am J Clin Nutr
 
1994
;
59
:
307
–16.
17.
Committee on Health and Statistics, Korean Pediatrics Society. 1998 Korean physical growth standards for children and adolescents. (In Korean). Seoul, Republic of Korea: Guang Mun Publishing Company,
1999
.
18.
National High Blood Pressure Education Program Working Group on High Blood Pressure in Children and Adolescents. The fourth report on the diagnosis, evaluation, and treatment of high blood pressure in children and adolescents.
Pediatrics
 
2004
;
114
:
555
–76.
19.
Agency for Technology and Standards. The Fifth National Anthropometic Survey of Korea. (In Korean). Seoul, Republic of Korea: Ministry of Commerce, Industry, and Energy,
2004
.
20.
National Cholesterol Education Program. Report of the Expert Panel on Blood Cholesterol Levels in Children and Adolescents. Bethesda, MD: National Institutes of Health,
1991
. (DHHS publication no. (NIH) 91-2732).
21.
Committee on Nutrition, American Academy of Pediatrics. Cholesterol in childhood.
Pediatrics
 
1998
;
101
:
141
–7.
22.
Freedman DS, Khan LK, Dietz WH, et al. Relationship of childhood obesity to coronary heart disease risk factors in adulthood: the Bogalusa Heart Study.
Pediatrics
 
2001
;
108
:
712
–18.
23.
Chu NF, Rimm EB, Wang DJ, et al. Clustering of cardiovascular disease risk factors among obese schoolchildren: the Taipei Children Heart Study.
Am J Clin Nutr
 
1998
;
67
:
1141
–6.
24.
Reinehr T, Andler W, Denzer C, et al. Cardiovascular risk factors in overweight German children and adolescents: relation to gender, age and degree of overweight.
Nutr Metab Cardiovasc Dis
 
2005
;
15
:
181
–7.
25.
Styne DM. Childhood and adolescent obesity. Prevalence and significance.
Pediatr Clin North Am
 
2001
;
48
:
823
–54.
26.
Williams CL, Hayman LL, Daniels SR, et al. Cardiovascular health in childhood: a statement for health professionals from the Committee on Atherosclerosis, Hypertension, and Obesity in the Young (AHOY) of the Council on Cardiovascular Disease in the Young, American Health Association.
Circulation
 
2002
;
106
:
143
–60.
27.
Akerblom HK, Viikari J, Raitakari OT, et al. Cardiovascular risk in Young Finns Study: general outline and recent developments.
Ann Med
 
1999
;
31
(suppl 1):
45
–54.
28.
Cho SJ, Park SJ, Hwang IT, et al. Risk factors for cardiovascular disease in obese children. (In Korean).
J Korean Pediatr Soc
 
2001
;
44
:
493
–500.
29.
Rosner B, Prineas R, Daniels SR, et al. Blood pressure differences between Blacks and Whites in relation to body size among US children and adolescents.
Am J Epidemiol
 
2000
;
151
:
1007
–19.