Association between Changes in Anthropometric Indices and in Fasting Insulin Levels among Healthy Korean Adolescents: The JS High School Study

BACKGROUND: This study investigated the association between changes in anthropometric indices and fasting insulin levels among healthy adolescents and whether the association differed by baseline obesity status. METHODS: This analysis was based on data collected for the JS High School study; 884 healthy adolescents aged 15 to 16 years followed up for 24 to 30 months were included. Changes in anthropometric indices and fasting insulin levels were computed as the difference between baseline and follow-up values. Multivariate linear regression models were used to determine the association between changes in anthropometric indices and fasting insulin levels. Based on body mass index (BMI)-for-age and waist circumference (WC)-for-age percentiles, participants were classified as normal weight (<85th percentile), overweight (85th percentile to <95th percentile), or obese (≥95th percentile). RESULTS: Changes in BMI, WC, waist-hip ratio, and waist-height ratio were significantly associated with changes in fasting insulin levels in both sexes (P<0.05). In analyses stratified by baseline obesity status, the association between change in BMI and change in fasting insulin was significantly stronger in overweight (males: standardized β=1.136; females: standardized β=1.262) and obese (males: standardized β=1.817; females: standardized β=2.290) participants than in those with normal weight (males: standardized β=0.957; females: standardized β=0.976) at baseline. Results were similar for changes in WC. CONCLUSION: Changes in anthropometric indices were positively associated with fasting insulin level increases. Moreover, those who were overweight or obese at baseline had a higher absolute increase in fasting insulin levels per one standard deviation unit increase in anthropometric indices than adolescents with normal weight.

Cohort Profile: The Cardiovascular and Metabolic Diseases Etiology Research Center Cohort in Korea

Mortalities from cardiovascular disease in Korea have decreased markedly over the past three decades. The major cardiovascular and metabolic risk factors, however, remain prevalent, and their burden on health is large. The Cardiovascular and Metabolic Diseases Etiology Research Center (CMERC) planned a cohort study in order to identify novel risk factors and to develop evidence-based prevention strategies of cardiovascular and metabolic diseases. The CMERC deliberately designed two prospective cohorts, a community-based general population cohort (the CMERC cohort) and its sister cohort (a hospital-based high-risk patient cohort), covering a broad spectrum of cardiovascular and metabolic diseases. This paper describes the CMERC cohort study of community-dwelling adults aged 30 to 64 years. A total of 8097 adults completed baseline measurement between 2013 and 2018. Baseline measurements assessed socio-demographic factors, medical history, health-related behaviors, psychological health, social network and support, anthropometry, body composition, and resting blood pressure and comprised electrocardiography, carotid artery ultrasonography, fasting blood analysis, and urinalysis. Both active follow-up through an annual telephone survey and a 5-year on-site health examination survey and passive follow-up through secondary data linkage with national databases, such as national death records, have been applied. Researchers interested in collaborative research may contact the corresponding author.

Sleep duration and chronic kidney disease: The Korean Genome and Epidemiology Study (KoGES)-Kangwha study

BACKGROUND/AIMS: Sleep duration affects health in various ways. The objective of this study was to investigate the associations of sleep duration with chronic kidney disease (CKD) in a Korean adult population. METHODS: This cross-sectional analysis was conducted for total of 1,360 participants who completed baseline health examinations for the Korean Genome and Epidemiology Study-Kangwha study in 2010 to 2011. Sleep habits were measured by an interviewer-assisted questionnaire. Sleep duration was calculated based on the number of hours per day participants had slept over the past 1 year. CKD was defined as either proteinuria or estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m². Multiple logistic regression models were applied to examine associations between sleep duration and CKD. RESULTS: Women with very long sleep duration (≥ 9 hours/day) were at significantly increased odds for having high serum creatinine (odds ratio [OR], 2.936; 95% confidence interval [CI], 1.176 to 7.326), low eGFR (OR, 3.320; 95% CI, 1.372 to 8.034), and CKD (OR, 3.112; 95% CI, 1.315 to 7.363), compared those with a typical sleep duration (7 to < 8 hours/day), after adjusting for sociodemographic status, socioeconomic status, health behaviors, comorbidities, and sleep quality. Among women, for every 1 hour increase in sleep duration per day, there was a 24.6% increase in the presence of CKD (OR, 1.246; 95% CI, 1.019 to 1.523). However, among men, sleep duration was not significantly associated with CKD. CONCLUSIONS: Very long sleep duration was independently associated with a higher prevalence of CKD among Korean women. Gender may influence this association.

Cardiovascular and Metabolic Diseases Etiology Research Center (CMERC) cohort: study protocol and results of the first 3 years of enrollment / 한국역학회지

Although the etiologies of cardiovascular disease (CVD) are widely understood, the goal of finding a globally effective solution for preventing CVD is unrealistic. Therefore, we aimed to conduct a community-based prospective study on the prevention and management of CVD in Korean adults. This study was designed to recruit 8,000 healthy adults over the course of 5 years. The baseline assessment includes a wide range of established CVD risk factors, including demographic characteristics, medical history, health behaviors, psychological conditions, body size and composition, blood pressure, the augmentation index, carotid ultrasonography, an electrocardiogram, and biochemical indicators, as well as some novel factors, such as social network characteristics, exposure to environmental pollutants, inflammatory markers, hemostatic markers, and immunosenescence markers. Annual telephone interviews and follow-up health examinations at 5-year intervals after the baseline assessment are planned to collect information on changes in health status and its determinants. Additionally, indirect follow-up using secondary data sources will be conducted to obtain information on health services utilization and death. So far, more than 6,000 adults have been enrolled during the first three and a half years, and almost all participants have been tracked by annual telephone follow-up surveys. The data have been uploaded to iCReaT, the clinical research information management system of the Korea National Institute of Health.

Cardiovascular and Metabolic Diseases Etiology Research Center (CMERC) cohort: study protocol and results of the first 3 years of enrollment / 한국역학회지

Although the etiologies of cardiovascular disease (CVD) are widely understood, the goal of finding a globally effective solution for preventing CVD is unrealistic. Therefore, we aimed to conduct a community-based prospective study on the prevention and management of CVD in Korean adults. This study was designed to recruit 8,000 healthy adults over the course of 5 years. The baseline assessment includes a wide range of established CVD risk factors, including demographic characteristics, medical history, health behaviors, psychological conditions, body size and composition, blood pressure, the augmentation index, carotid ultrasonography, an electrocardiogram, and biochemical indicators, as well as some novel factors, such as social network characteristics, exposure to environmental pollutants, inflammatory markers, hemostatic markers, and immunosenescence markers. Annual telephone interviews and follow-up health examinations at 5-year intervals after the baseline assessment are planned to collect information on changes in health status and its determinants. Additionally, indirect follow-up using secondary data sources will be conducted to obtain information on health services utilization and death. So far, more than 6,000 adults have been enrolled during the first three and a half years, and almost all participants have been tracked by annual telephone follow-up surveys. The data have been uploaded to iCReaT, the clinical research information management system of the Korea National Institute of Health.

Comparison of Formulas for Calculating Low-density Lipoprotein Cholesterol in General Population and High-risk Patients with Cardiovascular Disease

BACKGROUND AND OBJECTIVES: Low-density lipoprotein cholesterol (LDL-C), an established cardiovascular risk factor, can be generally determined by calculation from total cholesterol, high-density lipoprotein cholesterol, and triglyceride concentrations. The aim of this study was to compare LDL-C estimations using various formulas with directly measured LDL-C in a community-based group and hospital-based group among the Korean population. SUBJECTS AND METHODS: A total of 1498 participants were classified into four groups according to triglyceride concentrations as follows: <100, 100–199, 200–299, and ≥300 mg/dL. LDL-C was calculated using the Friedewald, Chen, Vujovic, Hattori, de Cordova, and Anandaraja formulas and directly measured using a homogenous enzymatic method. Pearson's correlation coefficients, intraclass correlation coefficients (ICC), Passing & Bablok regression, and Bland-Altman plots were used to evaluate the performance of six formulas. RESULTS: The Friedewald formula had the highest accuracy (ICC=0.977; 95% confidence interval 0.974-0.979) of all the triglyceride ranges, while the Vujovic formula had the highest accuracy (ICC=0.876; 98.75% confidence interval 0.668–0.951) in people with triglycerides ≥300 mg/dL. The mean difference was the lowest for the Friedewald formula (0.5 mg/dL) and the percentage error was the lowest for the Vujovic formula (30.2%). However, underestimation of the LDL-C formulas increased with triglyceride concentrations. CONCLUSION: The accuracy of the LDL-C formulas varied considerably with differences in triglyceride concentrations. The Friedewald formula outperformed other formulas for estimating LDL-C against a direct measurement and the Vujovic formula was suitable for hypertriglyceridemic samples; it could be used as an alternative cost-effective tool to measure LDL-C when the direct measurement cannot be afforded.

Inter-Arm Difference in Brachial Blood Pressure in the General Population of Koreans

BACKGROUND AND OBJECTIVES: We investigated the inter-arm difference in blood pressure of the general Korean population to identify associated factors. SUBJECTS AND METHODS: A total of 806 participants aged 30 to 64 years without history of major cardiovascular disease were analyzed in this cross-sectional study. They participated in the Cardiovascular and Metabolic Disease Etiology Research Center cohort study that began in 2013. Brachial blood pressure was measured simultaneously for both arms using an automated oscillometric device equipped with two cuffs in seated position. After five minutes of rest, systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured three times. The average of the three measurements was used for analysis. Multivariate logistic regression models were used to identify factors associated with inter-arm differences in blood pressure. RESULTS: The mean inter-arm difference was 3.3 mmHg for SBP and 2.0 mmHg for DBP. Large inter-arm differences (≥10 mmHg) in SBP and in DBP were found in 3.7% and 0.9% of subjects, respectively. A large inter-arm difference in SBP was associated with mean SBP (p=0.002) and C-reactive protein (p=0.014) while a large inter-arm different in DBP was only associated with body mass index (p=0.015). Sex, age, and anti-hypertensive medication use were not associated with differences in inter-arm blood pressure. CONCLUSION: Large inter-arm difference in blood pressure is only present in a small portion of healthy Korean adults. Our findings suggest that high SBP, chronic inflammation, and obesity may be associated with larger difference in inter-arm blood pressure.

Effects of Age, Sex, and Menopausal Status on Blood Cholesterol Profile in the Korean Population

BACKGROUND AND OBJECTIVES: To investigate age-specific and sex-specific distributions of blood cholesterol in the general Korean population. SUBJECTS AND METHODS: We analyzed data for 8284 men and 9246 women aged > or =10 years who participated in the fifth (2010-2012) Korea National Health and Nutrition Examination Survey. Age-specific means, medians, and selected percentiles were calculated for men, premenopausal women, and postmenopausal women. RESULTS: Median total cholesterol (TC) level increased with age across all age groups, from 147 to 196 mg/dL in males and from 159 to 210 mg/dL in females. Triglyceride (TG) levels increased with age in females; however, in males, TG levels rapidly increased during young adulthood, peaked at 50-54 years, and then decreased. High density lipoprotein-cholesterol (HDL-C) levels were higher in females than in males and decreased with increasing age in both males and females. Low density lipoprotein-cholesterol (LDL-C) levels increased with age across all age groups, from 89 to 127 mg/dL in males and from 82 to 113 mg/dL in females. Lipoprotein-cholesterol fraction (TC/HDL-C, LDL-C/HDL-C, TG/HDL-C, non-HDL-C) levels increased with age in females, but increased more rapidly in males during young adulthood and decreased after middle age. CONCLUSION: Blood cholesterol levels and lipoprotein-cholesterol fractions present different distributions by age, sex, and menopausal status.

Association between Serum 25-Hydroxyvitamin D Level and Insulin Resistance in a Rural Population

PURPOSE: A low serum 25-hydroxyvitamin D [25(OH)D] level in the blood has been correlated with an increased risk of diabetes mellitus; however, the association between serum 25(OH)D level and insulin resistance has not been established in a Korean rural population. The aim of this study was to investigate the independent association between serum 25(OH)D level and insulin resistance in rural Korean adults. MATERIALS AND METHODS: This study used data from the Korean Genome Epidemiology Study-Kangwha Study. In the 2011 study, 1200 adults completed health examinations. In an ancillary study, serum 25(OH)D level was measured in a subsample (n=813). After excluding those taking vitamin D supplements, a cross-sectional analysis was carried out on 807 participants (324 men and 483 women) aged 40 to 89 years old. Measured from overnight fasting blood samples, glucose and insulin levels were used to calculate the homeostasis model assessment for insulin resistance (HOMA-IR). Measures of glucose, insulin, and HOMA-IR were log-transformed for parametric tests. RESULTS: Serum 25(OH)D level was inversely associated with HOMA-IR (beta=-0.003, p=0.039) in a univariate analysis. However, the association was not significant after adjustment for sex and age (beta=-0.002, p=0.123) or after adjustment for sex, age, body mass index, smoking status, alcohol intake, and regular exercise (beta=-0.003, p=0.247). CONCLUSION: Our findings suggest that vitamin D is not independently associated with insulin resistance in Korean men and women.

Factors Associated with a Low-sodium Diet: The Fourth Korean National Health and Nutrition Examination Survey / 한국역학회지

OBJECTIVES: The low-sodium diet is a known preventive factor for hypertension and cardiovascular disease. Factors associated with low-sodium diets should be identified to reduce sodium intake effectively. This study was conducted to identify factors correlated with a low-sodium diet. METHODS: This cross-sectional study analyzed data from a total of 14,539 Koreans aged 20 years or older, who participated in the Fourth (2007-2009) Korean National Health and Nutrition Examination Survey. A low-sodium diet was defined as having or =1 time/day, respectively. CONCLUSIONS: Our study suggests that sex, age, number of family members, occupation, total energy intake, and lower frequency of eating out were associated with a low-sodium diet in Korean adults.

Prevalence of Dyslipidemia among Korean Adults: Korea National Health and Nutrition Survey 1998-2005

BACKGROUND: Dyslipidemia is a disorder of lipid metabolism, including elevated total cholesterol, elevated triglyceride, elevated low density lipoprotein cholesterol (LDL-C), and decreased high density lipoprotein cholesterol (HDL-C). The objective of this study was to investigate recent changes in the prevalence of dyslipidemia and also the rates of awareness, treatment, and control of dyslipidemia among Korean adults. METHODS: Dyslipidemia is defined according to the National Cholesterol Education Program-Adult Treatment Panel III as total cholesterol > or =240 mg/dL, LDL-C > or =160 mg/dL, HDL-C or =200 mg/dL. The prevalence of dyslipidemia was estimated for adults aged > or =20 years using the Korea National Health and Nutrition Survey (KNHANES) in 1998 (n=6,923), 2001 (n=4,882), and 2005 (n=5,323). Rates of awareness, treatment and control of dyslipidemia were calculated for adults aged > or =30 years using the KNHANES in 2005 (n=4,654). RESULTS: The prevalence of dyslipidemia (aged > or =20 years) increased from 32.4% in 1998 to 42.6% in 2001 and 44.1% in 2005. Compared with the KNHANES in 1998, the prevalence of dyslipidemia was 47% (95% confidence interval [CI], 35% to 59%) higher in 2001 and 61% (95% CI, 49% to 75%) higher in 2005. In 2005, only 9.5% of people with dyslipidemia were aware of the disease, 5.2% used lipid-lowering medication, and 33.2% of patients with treatment reached treatment goals. CONCLUSION: The prevalence of dyslipidemia in Korea gradually increased between 1998 and 2005. These findings suggest that more intense efforts for the prevention and treatment of dyslipidemia may lead to further improvement in the management of dyslipidemia.

The Association Between Serum Albumin Levels and Metabolic Syndrome in a Rural Population of Korea / 예방의학회지

OBJECTIVES: A positive association between serum albumin levels and metabolic syndrome has been reported in observation studies, but it has not been established in the Korean population. The purpose of this study was to evaluate the association between serum albumin levels and the presence of metabolic syndrome among a sample of apparently healthy Korean adults. METHODS: This cross-sectional study analyzed data of 3189 community-dwelling people (1189 men and 2000 women) who were aged 40 to 87 years and were living in a rural area in Korea. Serum albumin levels were classified into quartile groups for each sex. Metabolic syndrome was defined according to the National Cholesterol Education Program Adult Treatment Panel III guidelines with an adjusted waist circumference cut-off value (> or =90 cm for men and > or =85 cm for women). An independent association between serum albumin levels and metabolic syndrome was assessed by multiple logistic regression analysis. RESULTS: Higher serum albumin levels were associated with increased prevalence of metabolic syndrome. The odds ratio (95% confidence interval) of the prevalence of metabolic syndrome for the highest versus the lowest serum albumin quartiles was 2.81 (1.91 to 4.14) in men and 1.96 (1.52 to 2.52) in women, after adjusting for age, smoking status, alcohol consumption, and physical activity. When each metabolic abnormality was analyzed separately, higher serum albumin levels were significantly associated with hypertriglyceridemia and hyperglycemia in both sexes, and with abdominal obesity in men. CONCLUSIONS: These results suggest that higher serum albumin levels are positively associated with an increased risk of metabolic syndrome in Korean adults.

Association between Pulse Pressure and Carotid Intima-Media Thickness in Healthy Adolescents: Jangseong High School Study

BACKGROUND: Wide pulse pressure associates with atherosclerosis, but it is unclear whether pulse pressure within a relatively normal range is associated with atherosclerosis in younger populations. The aim of this study was to investigate the association between pulse pressure and the carotid intima-media thickness (IMT) in healthy adolescents. METHODS: Study participants included 250 (129 males and 121 females) adolescents who were 17 to 19 years old and in the third grade of a high school in Jangseong, Korea between November 20 and December 1, 2009. Pulse pressure was determined as the difference between systolic blood pressure and diastolic blood pressure which were measured with an oscillometric sphygmomanometer. IMT values were ultrasonographically measured at right and left common carotid arteries, and average of the mean IMT at each artery was used for analysis. RESULTS: There was a significant correlation between pulse pressure and carotid IMT before (Pearson coefficient r = 0.2037, p = 0.001) and after (r = 0.1479, p = 0.020) adjustment for sex. When adjusted for sex, age, waist circumference, fasting blood glucose, and total/high-density lipoprotein cholesterol ratio, 10 mm Hg increase in pulse pressure was associated with increase of IMT in total (beta = 10.9 microm, p = 0.003), in males (beta = 17.3 microm, p < 0.001), but not in females (beta = 3.609 microm, p = 0.518). CONCLUSIONS: This study suggests that higher pulse pressure may be associated with increased carotid IMT even in healthy male adolescents.

Association Between Serum Uric Acid Level and Metabolic Syndrome / 예방의학회지

OBJECTIVES: Serum uric acid levels have been reported to be associated with a variety of cardiovascular conditions. However, the direct association between uric acid levels and metabolic syndrome remains controversial. Thus, we evaluated the association of serum uric acid levels and metabolic syndrome in a community-based cohort study in Korea. METHODS: We performed cross-sectional analysis of baseline data of 889 males and 1491 females (aged 38 to 87) who participated in baseline examinations of the Korean Genome and Epidemiology Study: Kanghwa study. Blood samples were collected after at least an 8 hour fast. Uric acid quartiles were defined as follows: or =6.5 mg/dL in males; and or =5.1 mg/dL in females. Metabolic syndrome was defined by the National Cholesterol Education Program Adult Treatment Panel III Criteria with adjusted waist circumference cutoffs (90 cm for males; 80 cm for females). The association between serum uric acid quartiles and metabolic syndrome was assessed using multivariate logistic regression. RESULTS: The odds ratio for having metabolic syndrome in the highest versus lowest quartiles of serum uric acid levels was 2.67 (95% confidence interval [CI], 1.60 to 4.46) in males and 2.14 (95% CI, 1.50 to 3.05) in females after adjusting for age, smoking, alcohol intake, body mass index, total cholesterol, HbA1c, albumin, gamma-glutamyltransferase, blood urea nitrogen, and log C-reactive protein. The number of metabolic abnormalities also increased gradually with increasing serum uric acid levels (adjusted p for trend < 0.001 in both sexes). CONCLUSIONS: Higher serum uric acid levels are positively associated with the presence of metabolic syndrome in Korean males and females.

Association Between Body Mass Index and Asthma Symptoms Among Korean Children: A Nation-Wide Study

The purpose of this study was to investigate the association between body mass index (BMI) and the prevalence of wheeze using nation-wide cross-sectional study in Korean children. Total 50,200 children from 427 elementary schools were randomly selected according to residential areas (metropolitan, provincial, rural, and industrial areas) by the cluster sampling method. The International Study of Asthma and Allergies in Childhood (ISAAC) questionnaires were used to measure the prevalence of wheeze. Among 31,026 respondents, 25,322 were analyzed. BMI was classified into quartiles based on BMI-for-age percentile. In all residential areas, pets at home and visible mold or moisture were associated with an increased prevalence of wheeze in both genders. However, other living environment factors were not consistently associated among residential areas and gender. Among girls, lowest BMI was negatively associated with prevalence of wheeze and highest BMI was positively associated in all residential areas. In multilevel logistic regression analysis, environmental tobacco smoking exposure, pets at home, visible mold or moisture, and being in the lowest and highest BMI quartile were significantly associated with the prevalence of wheeze in both genders. BMI has become an important risk factor for asthma symptoms among Korean children.

Association between Hypertension and Pulmonary Function in Rural Adults in Korea / 예방의학회지

OBJECTIVES: Whilst hypertension exerts a negative effect on several organs there have been few studies regarding its effect on pulmonary function. The objective of this study was to examine the relationship between hypertension and pulmonary function in rural Korean adults. METHODS: In 2006, 2534 people were recruited, aged 40 to 70, in Kangwha County. We selected 1454 (male: 624, female: 830) participants whose pulmonary function results were repeatable. Blood pressure (BP) was measured twice and the average calculated. Participants were divided into two groups (hypertensive group and non-hypertensive group) in accordance with The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure. Pulmonary function was measured by dry rolling seal spirometry. Forced expiratory volume in the one second and forced vital capacity were converted into percent-predicted values based on average pulmonary function amongst Koreans. RESULTS: The number of hypertensive participants in the present study was 460 (male: 205, female: 255) and the number of non-hypertensive participants was 994 (male: 419, female: 575). Our findings have shown that the mean values for expiratory volume in the one second and forced vital capacity were significantly lower for hypertensive people than for non-hypertensive people, among women (P=0.002 for forced expiratory volume in the one second, P<0.001 for forced vital capacity volume). Odds ratio analysis revealed that hypertensive participants were more likely to have lower pulmonary function than non-hypertensive participants, again significantly among women. CONCLUSIONS: The pulmonary function of hypertensive women was significantly lower than that of non-hypertensive women aged 40-70.