Only a few studies have explored nationwide trends in lipid profiles among Asian adolescents. We aimed to assess trends in lipid profiles and the associated lifestyle factors among Korean children.
We analyzed data for 2,094 adolescents who were aged 10–18 years and had participated in the Korea National Health and Nutrition Examination Surveys in 1998 and 2010.
During 1998–2010, the prevalence of obesity significantly increased in boys, but no changes were observed in girls. Over this period, there was a small but significant decrease in the mean low-density lipoprotein (LDL)-cholesterol level in boys (1998, 87.5 mg/dL; 2010, 83.6 mg/dL;
Although the prevalence of obesity in boys increased, favorable or constant trends in lipid profiles were observed among Korean adolescents during 1998–2010. Decrease in breakfast skipping and increase in regular exercise may have contributed to these trends.
The prevalence of obesity in children and adolescents has increased dramatically worldwide in the past three decades. The Fels Longitudinal Study showed that obesity indices, including body mass index (BMI), waist circumference/height, and percent body fat, are significantly higher in adolescents born in the 1990s than in those born in previous decades in the United States (US)
Growing evidence indicates that obesity in early life is one of the strongest risk factors for dyslipidemia, which increases the risks for cardiovascular disease in adulthood
Although the prevalence of dyslipidemia in adolescents and its associated risk factors have been investigated in several countries
Data were obtained from the KNHANES, a nationally representative, cross-sectional survey of the health and nutritional status of Korean civilians, conducted in 1998 and 2010, by the Korean Ministry of Health and Welfare. Details of the design of the KNHANES are available on the KNHANES website (
Experienced examiners performed anthropometric measurements. Height was measured to the nearest 0.1 cm on a stadiometer (Seriter, Holtain Ltd., Crymych, UK, in 1998; SECA 225, SECA Deutschland, Hamburg, Germany, in 2010). Body weight was measured to the nearest 0.1 kg on a balance beam scale (Giant 150N, HANA, Seoul, Korea), with the subject wearing light clothing and no shoes. BMI was calculated as the body weight divided by the square of the height (kg/m2). Waist circumference, defined as the narrowest point between the lower borders of the rib cage and the iliac crest, was measured to the nearest 0.1 cm following the end of a normal expiration. Obesity level was categorized according to the age and sex specific percentiles for BMI of national reference standards
Dietary assessment of daily energy intake was performed in subjects through a 24-hour recall interview. Breakfast skipping was defined as regularly not eating breakfast more than 5 times per week. Alcohol consumption was categorized as "Yes" when the subjects reported a consumption of alcohol more than once per month in the 1-year period preceding the interview. Smoking was categorized as "Yes" when the subjects reported smoking more than once per month in the 1-year period preceding the interview. Physical activity was self-reported using the International Physical Activity Questionnaire. Regular exercise was categorized as "Yes" when the subjects reported moderate physical activity for more than 20 minutes at a time and more than 3 times per week. Moderate physical activity was defined as physical activity that causes a slight increase in breathing or heart rate, and includes activities such as carrying light loads, bicycling at a regular pace, or playing doubles tennis.
Fasting blood samples were obtained from the antecubital vein following a 10-hour overnight fast. In 1998, the fasting plasma concentrations of total cholesterol, LDL-cholesterol, triglycerides, and high-density lipoprotein (HDL) cholesterol were measured enzymatically using a 747 Chemistry analyser (Hitachi, Tokyo, Japan). In 2010, the fasting plasma concentrations of total cholesterol, triglycerides, and HDL cholesterol were measured enzymatically using a Hitachi Automatic Analyzer 7600 (Hitachi, Tokyo, Japan). Most of the LDL-cholesterol levels in 2010 were calculated with the Friedewald equation (total cholesterol – [HDL-cholesterol + triglycerides/5]). Only for the samples with triglycerides greater than 400 mg/dL, LDL-cholesterol were measured using a Hitachi Automatic Analyzer 7600 (Hitachi). The diagnostic cutoff points for adolescent dyslipidemia were based on guidelines from the American Heart Association
Hypercholesterolemia was defined as total cholesterol levels>200 mg/dL, hypo-HDL-cholesterolemia was defined as HDL-cholesterol levels<40 mg/dL, and hypertriglyceridemia was defined as triglyceride levels>150 mg/dL. Hyper-LDL-cholesterolemia was defined as LDL-cholesterol levels>130 mg/dL. Dyslipidemia was diagnosed when subjects have at least one of hypercholesterolemia, hypertriglyceridemia, hyper-LDL-cholesterolemia, and hypo-HDL-cholesterolemia.
All data analyses were conducted using SAS ver. 9.2 (SAS Institute Inc., Cary, NC, USA). Survey design parameters, including clusters, stratums, and weights, were utilized in all statistical analyses. Information of nonparticipants was included in weighting of the statistical weighting. Therefore, the means and prevalence estimated in this study represented the overall estimates for the total Korean population aged 10–18 years. PROC SURVEYMEANS and PROC SURVEYFREQ were used to estimate means and prevalence, respectively. PROC SURVEYREG and PROC SURVEYFREQ were used to assess the differences in continuous and categorical variables, respectively, between genders and between the 1998 and 2010 populations. Multivariable logistic regression analyses, using PROC SURVEYLOGISTIC, were conducted to assess the associations of dyslipidemia with obesity level, central obesity, breakfast skipping, alcohol consumption, smoking, and regular exercise. For all analyses,
The age and anthropometric measurements of the participants are presented in
The trends in the blood lipid profile and prevalence of dyslipidemia are presented in
Lifestyle characteristics of the participants are presented in
In multivariable logistic regression analyses adjusted for age (
In this study, we demonstrated favourable or constant trends in lipid profiles among Korean adolescents from 1998 to 2010, despite increased prevalence of obesity in boys. This result is interesting because the association between obesity and unfavourable lipid status has been well established in multiple studies
Previous studies have shown that high consumption of energy-dense food increases the risk of childhood obesity. Among American children and adolescents, the total energy intake has increased in the 1990s–2000s as compared to the 1970s; consumption of delivery food or eating out has also increased. This trend has coincided with the increased prevalence of obesity
Breakfast is an important meal, as it breaks the overnight fasting period and ensures the supply of glucose and other essential nutrients to the body. Eating a fibre-rich breakfast reduces between-meal hypoglycaemia and reduces appetite and energy intake through the release of gut hormones that act as satiety factors. As a result, skipping breakfast has been reported to be associated with a higher fat and energy intake, resulting in weight gain in children and adolescents
Evidence that skipping breakfast may affect lipid profile in adult populations is emerging in Western countries. In a longitudinal study in Australia, adults who skipped breakfast in both childhood (age, 9–15 years) and adulthood (age, 26– 36 years) had higher total cholesterol and LDL-cholesterol levels than those who ate breakfast at both time points
Many studies report that physical activity has beneficial effects on the lipid profile of adults. While few studies have suggested that regular exercise can reduce LDL-cholesterol
The effects of alcohol on LDL-cholesterol appear to vary by types and patterns of alcohol intake, population, and sex. Alcohol consumption was associated with decreased LDL-cholesterol levels in Chinese
It is noteworthy that breakfast skipping and regular exercise, important determinants of lipid profile, were significantly associated with socio-economic status in the present study (data not shown). For instance, breakfast skipping rates were significantly higher in subjects in the lowest household income quartile than those in the highest quartile. In contrary, regular exercise rates were lower in subjects in the lowest household income quartile than those in the highest quartile. Therefore, lifestyle modifications to prevent adverse lipid metabolism should be emphasized particularly in children and adolescents in low socio-economic status.
There are some limitations to this study. First, while LDL-cholesterol levels were directly measured in 1998, they were calculated with Friedewald formula in 2010, therefore there is some possibility of underestimation of LDL-cholesterol levels in 2010. A recent study among Korean adults demonstrated that the Friedewald formula has shown to underestimate LDL-cholesterol levels when triglyceride levels are greater than 298 mg/dL, and it accurately estimates directly-measured LDL-cholesterol levels when triglyceride levels are between 36 and 298 mg/dL
In conclusion, favourable or constant trends of LDL-cholesterol levels in boys and triglyceride levels in girls were observed, despite the increased prevalence of obesity in boys. Improvements in the prevention of breakfast skipping and in the levels of regular exercise may contribute to favourable trends observed in the lipid profile of adolescents. We suggest that policies, surveys, and education aimed at improving childhood health and preventing cardiovascular disease in adulthood need to focus on both nutrition and exercise for the greatest impact.
We thank the Korea Centers for Disease Control and Prevention for providing the data.
Variable | Boys | Girls | ||||
---|---|---|---|---|---|---|
1998 | 2010 | 1998 | 2010 | |||
Number | 661 | 443 | 617 | 370 | ||
Age (yr) | 14.1±0.1 | 14.2±0.1 | 0.367 | 14.2±0.1 | 14.1±0.2 | 0.668 |
Height (cm) | 162.6±0.3 | 164.1±0.5 | 0.022 | 156.2±0.3 | 156.8±0.4 | 0.065 |
Weight (kg) | 53.5±0.5 | 57.1±0.7 | <0.001 | 48.7±0.4 | 50.1±0.7 | 0.047 |
Waist circumference (cm) | 69.7±0.4 | 71.4±0.6 | 0.020 | 66.7±0.4 | 67.2±0.5 | 0.543 |
Body mass index (kg/m2) | 19.9±0.1 | 20.9±0.2 | <0.001 | 19.8±0.1 | 20.3±0.2 | 0.092 |
Obesity level* (%) | ||||||
Normal weight | 87.7 | 80.3 | 0.003 | 83.3 | 81.9 | 0.460 |
Overweight | 8.4 | 12.5 | 11.5 | 10.6 | ||
Obese | 3.9 | 7.2 | 5.2 | 7.5 |
Values are presented as mean±standard error of mean unless otherwise indicated.
*Obesity level was determined according to the sex and age-specific body mass index (BMI) percentile: normal (BMI<85th percentile), overweight (BMI≥ 85th percentile and <95th percentile), and obese (BMI≥95th percentile).
Variable | Boys | Girls | ||||
---|---|---|---|---|---|---|
1998 | 2010 | 1998 | 2010 | |||
Total cholesterol (mg/dL) | 156.6±1.2 | 152.8±1.3 | 0.072 | 165.7±1.3 | 163.3±1.6 | 0.155 |
HDL-cholesterol (mg/dL) | 52.9±0.6 | 52.3±0.5 | 0.554 | 53.9 ±0.6 | 55.5 ±0.7 | 0.111 |
LDL-cholesterol (mg/dL) | 87.5±1.0 | 83.6±1.1 | 0.019 | 93.6 ±1.1 | 91.0±1.5 | 0.106 |
Triglycerides (mg/dL) | 81.2±1.9 | 84.7±2.9 | 0.889 | 90.8 ±2.3 | 85.8 ±3.6 | 0.020 |
Hypercholesterolemia* (%) | 7.1 | 4.0 | 0.066 | 10.2 | 7.6 | 0.317 |
Hypertriglyceridemia† (%) | 10.7 | 8.2 | 0.202 | 10.3 | 6.7 | 0.138 |
Hyper-LDL-cholesterolemia‡ (%) | 5.0 | 3.8 | 0.419 | 7.3 | 3.6 | 0.083 |
Hypo-HDL-cholesterolemia§ (%) | 6.5 | 10.1 | 0.058 | 8.8 | 7.5 | 0.552 |
Dyslipidemia∥ (%) | 19.6 | 19.8 | 0.937 | 25.1 | 18.3 | 0.052 |
Values are presented as mean±standard error of mean unless otherwise indicated.
HDL, high-density lipoprotein; LDL, low-density lipoprotein.
*Total cholesterol level>200 mg/dL. †Triglycerides level>150 mg/dL. ‡LDL-cholesterol level>130 mg/dL. §HDL-cholesterol level<40 mg/dL. ∥Had at least one of the following: hypercholesterolemia, hypertriglyceridemia, hyper-LDL-cholesterolemia, and hypo-HDL-cholesterolemia
Variable | Boys | Girls | ||||
---|---|---|---|---|---|---|
1998 | 2010 | 1998 | 2010 | |||
Daily energy intake | ||||||
Energy (kcal/day) | 2,349.3±50.2 | 2,401.3±63.4 | 0.573 | 1,884.7±40.3 | 1,902.3±64.3 | 0.774 |
Protein (g/day) | 83.8±2.4 | 86.6±2.8 | 0.505 | 65.6±1.9 | 65.4±2.7 | 0.955 |
Fat (g/day) | 57.7±1.8 | 64±2.6 | 0.052 | 45.1±1.8 | 51.1±3 | 0.074 |
Carbohydrate (g/day) | 373.8±8.1 | 367±9.3 | 0.559 | 306.7±5.8 | 296.4±9.1 | 0.373 |
Breakfast skipping* (%) | 37.0 | 17.8 | <0.001 | 42.1 | 19.8 | <0.001 |
Alcohol drinking† (%) | 16.8 | 12.6 | 0.068 | 13.3 | 6.4 | 0.003 |
Smoking‡ (%) | 7.9 | 8.2 | 0.887 | 1.7 | 2.8 | 0.315 |
Regular exercise§ (%) | 21.6 | 36.1 | <0.001 | 6.3 | 16.5 | <0.001 |
Values are presented as mean±standard error of mean unless otherwise indicated.
*Breakfast skipping was defined as regularly not eating breakfast more than 5 times per week. †Alcohol drinking was categorized as "Yes" when the subjects consumed alcohol more than once per month in the year preceding the interview. ‡Smoking was categorized as "Yes" when the subjects smoke more than once per month in the year preceding the interview. §Regular exercise was categorized as "Yes" when the subjects performed moderate physical activity for more than 20 minutes at a time and more than 3 times per week.
Variable | Boys | Girls | ||||
---|---|---|---|---|---|---|
OR | 95% CI | OR | 95% CI | |||
Obesity level* (%) | ||||||
Normal weight | Reference | Reference | ||||
Overweight | 5.28 | 2.66-10.49 | 0.061 | 1.24 | 0.41-3.75 | 0.102 |
Obese | 6.53 | 2.92-14.59 | 0.015 | 8.29 | 2.56-26.89 | 0.002 |
WC percentile | ||||||
<90 percentile | Reference | Reference | ||||
≥90 percentile | 5.18 | 2.29-11.73 | <0.001 | 2.85 | 1.18-6.90 | 0.020 |
Breakfast skipping† | ||||||
Yes | 1.42 | 0.44-4.58 | 0.553 | 1.3 | 0.5-3.41 | 0.589 |
No | Reference | Reference | ||||
Alcohol drinking‡ | ||||||
Yes | 0.97 | 0.35-2.7 | 0.954 | 2.44 | 0.28-20.99 | 0.417 |
No | Reference | Reference | ||||
Smoking§ | ||||||
Yes | 0.59 | 0.2-1.72 | 0.330 | 1.9 | 0.32-11.45 | 0.483 |
No | Reference | Reference | ||||
Regular exercise∥ | ||||||
Yes | 0.91 | 0.52-1.61 | 0.757 | 2.02 | 0.69-5.91 | 0.120 |
No | Reference | Reference |
OR, odds ratio; CI, confidence interval; WC, waist circumference.
*Obesity level was determined according to the gender and age-specific body mass index (BMI) percentile: normal (BMI<85th percentile), overweight (BMI≥85th percentile and <95th percentile) and obese (BMI≥95th percentile). †Breakfast skipping was defined as regularly not eating breakfast more than 5 times per week. ‡Alcohol drinking was categorized as "Yes" when the subjects consumed alcohol more than once per month in the year preceding the interview. §Smoking was categorized as "Yes" when the subjects smoke more than once per month in the year preceding the interview. ∥Regular exercise was categorized as "Yes" when the subjects performed moderate physical activity for more than 20 minutes at a time and more than 3 times per week.
Variable | Hypercholesterolemia | Hypertriglyceridemia | Hyper-LDL-cholesterolemia | Hypo-HDL-cholesterolemia | ||||
---|---|---|---|---|---|---|---|---|
OR | 95% CI | OR | 95% CI | OR | 95% CI | OR | 95% CI | |
Breakfast skipping† | ||||||||
Yes | 1.39 | 0.21-9.30 | 0.63 | 0.14-2.84 | 5.77* | 1.02-33.28 | 1.24 | 0.27-5.77 |
No | Reference | Reference | Reference | Reference | ||||
Alcohol drinking‡ | ||||||||
Yes | - | - | 2.12 | 0.61-7.34 | 7.17 | 0.23-22.5 | 2.46 | 0.54-11.29 |
No | Reference | Reference | Reference | Reference | ||||
Smoking§ | ||||||||
Yes | - | - | - | - | 9.60 | 0.30-30.6 | - | - |
No | Reference | Reference | Reference | Reference | ||||
Regular exercise∥ | ||||||||
Yes | 1.45 | 0.38-5.56 | 1.11 | 0.59-2.10 | - | - | 0.40* | 0.16-0.98 |
No | Reference | Reference | Reference | Reference |
OR, odds ratio; CI, confidence interval; LDL, low-density lipoprotein; HDL, high-density lipoprotein.
*
Variable | Hypercholesterolemia | Hypertriglyceridemia | Hyper-LDL-cholesterolemia | Hypo-HDL-cholesterolemia | ||||
---|---|---|---|---|---|---|---|---|
OR | 95% CI | OR | 95% CI | OR | 95% CI | OR | 95% CI | |
Breakfast skipping† | ||||||||
Yes | 1.31 | 0.33-5.10 | 2.27* | 1.02-5.31 | 1.16 | 0.16-8.17 | 1.36 | 0.29-6.31 |
No | Reference | Reference | Reference | Reference | ||||
Alcohol drinking‡ | ||||||||
Yes | 2.70 | 0.26-27.6 | - | - | - | - | 3.18 | 0.18-55.95 |
No | Reference | Reference | Reference | Reference | ||||
Smoking§ | ||||||||
Yes | - | - | - | - | 1.42 | 0.06-32.83 | - | - |
No | Reference | Reference | Reference | Reference | ||||
Regular exercise∥ | ||||||||
Yes | 1.73 | 0.50-5.96 | 0.59 | 0.15-2.37 | 5.74 | 0.67-49.36 | 3.35 | 0.77-14.56 |
No | Reference | Reference | Reference | Reference |
OR, odds ratio; CI, confidence interval; LDL, low-density lipoprotein; HDL, high-density lipoprotein.
*