Calibration of High-Density Lipoprotein Cholesterol Values From the Korea National Health and Nutrition Examination Survey Data, 2008 to 2015

BACKGROUND: For correct interpretation of the high-density lipoprotein cholesterol (HDL-C) data from the Korea National Health and Nutrition Examination Survey (KNHANES), the values should be comparable to reference values. We aimed to suggest a way to calibrate KNHANES HDL-C data from 2008 to 2015 to the Centers for Disease Control and Prevention (CDC) reference method values. METHODS: We derived three calibration equations based on comparisons between the HDL-C values of the KNHANES laboratory and the CDC reference method values in 2009, 2012, and 2015 using commutable frozen serum samples. The selection of calibration equation for correcting KNHANES HDL-C in each year was determined by the accuracy-based external quality assurance results of the KNHANES laboratory. RESULTS: Significant positive biases of HDL-C values were observed in all years (2.85-9.40%). We created the following calibration equations: standard HDL-C=0.872×[original KNHANES HDL-C]+2.460 for 2008, 2009, and 2010; standard HDL-C=0.952×[original KNHANES HDL-C]+1.096 for 2012, 2013, and 2014; and standard HDL-C=1.01×[original KNHANES HDL-C]-3.172 for 2011 and 2015. We calibrated the biases of KNHANES HDL-C data using the calibration equations. CONCLUSIONS: Since the KNHANES HDL-C values (2008-2015) showed substantial positive biases compared with the CDC reference method values, we suggested using calibration equations to correct KNHANES data from these years. Since the necessity for correcting the biases depends on the characteristics of research topics, each researcher should determine whether to calibrate KNHANES HDL-C data or not for each study.

An Overview of Ophthalmologic Survey Methodology in the 2008-2015 Korean National Health and Nutrition Examination Surveys

The Korea National Health and Nutrition Examination Survey (KNHANES) is a national program designed to assess the health and nutritional status of the noninstitutionalized population of South Korea. The KNHANES was initiated in 1998 and has been conducted annually since 2007. Starting in the latter half of 2008, ophthalmologic examinations were included in the survey in order to investigate the prevalence and risk factors of common eye diseases such as visual impairment, refractive errors, strabismus, blepharoptosis, cataract, pterygium, diabetic retinopathy, age-related macular degeneration, glaucoma, dry eye disease, and color vision deficiency. The measurements included in the ophthalmic questionnaire and examination methods were modified in the KNHANES IV, V, and VI. In this article, we provide detailed information about the methodology of the ophthalmic examinations in KNHANES in order to aid in further investigations related to major eye diseases in South Korea.

Body Fat Percentile Curves for Korean Children and Adolescents: A Data from the Korea National Health and Nutrition Examination Survey 2009-2010

A valid assessment of obesity in children and adolescents is important due to significant change in body composition during growth. This study aimed to develop percentile curves of body fat and fat free mass using the Lambda, Mu, and Sigma method, and to examine the relationship among body mass index (BMI), fat mass and fat free mass in Korean children and adolescents, using the Korea National Health and Nutrition Examination Survey (KNHANES) 2009-2010. The study subjects were 834 for boys and 745 for girls aged between 10 and 18 yr. Fat mass and fat free mass were measured by dual-energy x-ray absorptiometry. The patterns of development in body fat percentage, fat mass and fat free mass differed for boys and girls, showing a decreased fat mass with an increased fat free mass in boys but gradual increases with age in girls. The considerable proportion of boys and girls with relatively normal fat mass appeared to be misclassified to be at risk of overweight based on the BMI criteria. Therefore, the information on the percentiles of body fat and fat free mass with their patterns would be helpful to complement assessment of overweight and obesity based on BMI for Korean children and adolescents.

Prevalence of Chronic Obstructive Pulmonary Disease in Korea: The Result of Forth Korean National Health and Nutrition Examination Survey / 결핵및호흡기질환

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is a major cause of chronic morbidity and mortality throughout the world and is the only major disease that is continuing to increase in both prevalence and mortality. The second Korean National Health and Nutrition Survey revealed that the prevalence of COPD in Korean subjects aged > or =45 years was 17.2% in 2001. Further surveys on the prevalence of COPD were not available until 2007. Here, we report the prevalence of spirometrically detected COPD in Korea, using data from the fourth Korean National Health and Nutrition Survey (KNHANES IV) which was conducted in 2007~2009. METHODS: Based on the Korean Statistical Office census that used nationwide stratified random sampling, 10,523 subjects aged > or =40 years underwent spirometry. Place of residence, levels of education, income, and smoking status, as well as other results from a COPD survey questionnaire were also assessed. RESULTS: The prevalence of COPD (defined as forced expiratory volume in 1 sec/forced vital capacity or =40 years) was 12.9% (men, 18.7%; women, 7.5%). In total, 96.5% of patients with COPD had mild-to-moderate disease; only 2.5% had been diagnosed by physicians, and only 1.7% had been treated. The independent risk factors for COPD were smoking, advanced age, and male gender. CONCLUSION: The prevalence of COPD was 12.9% in the KNHANES IV data. Most patients with COPD were undiagnosed and untreated. Based on these results, a strategy for early COPD intervention is warranted in high risk subjects.

Prevalence of Eye Diseases in South Korea: Data from the Korea National Health and Nutrition Examination Survey 2008-2009

PURPOSE: The aim of this study is to report on preliminary data regarding the prevalence of major eye diseases in Korea. METHODS: We obtained data from the Korea National Health and Nutrition Examination Survey, a nation-wide cross-sectional survey and examinations of the non-institutionalized civilian population in South Korea (n = 14,606), conducted from July 2008 to December 2009. Field survey teams included an ophthalmologist, nurses, and interviewers, traveled with a mobile examination unit and performed interviews and ophthalmologic examinations. RESULTS: The prevalence of visual impairment, myopia, hyperopia and astigmatism in participants over 5 years of age was 0.4 +/- 0.1%, 53.7 +/- 0.6%, 10.7 +/- 0.4%, and 58.0 +/- 0.6%, respectively. The prevalence of strabismus and blepharoptosis in participants over 3 years of age was 1.5 +/- 0.1% and 11.0 +/- 0.8%, respectively. In participants over 40 years of age, the prevalence of cataract, pterygium, early and late age-related macular degeneration, diabetic retinopathy and glaucoma was 40.2 +/- 1.3%, 8.9 +/- 0.5%, 5.1 +/- 0.3%, 0.5 +/- 0.1%, 13.4 +/- 1.5%, and 2.1 +/- 0.2%, respectively. CONCLUSIONS: This is the first nation-wide epidemiologic study conducted in South Korea for assessment of the prevalence of eye diseases by both the Korean Ophthalmologic Society and the Korea Center for Disease Control and Prevention. This study will provide preliminary information for use in further investigation, prevention, and management of eye diseases in Korea.

Green Tea Consumption and Stomach Cancer Risk: A Meta-Analysis / 한국역학회지

OBJECTIVES: Green tea has been suggested to have a chemopreventive effect against various cancers including stomach cancer. The aim of this study is to elucidate the relationship between green tea consumption and stomach cancer risk by meta-analysis. METHODS: Eighteen observational studies were identified using MEDLINE, THE COCHRANE LIBRARY, RISS, and a manual search. Summary relative risks/odds ratios (RR/ORs) for the highest versus non/lowest green tea consumption levels were calculated on the basis of fixed and random effect models. Subgroup analyses were used to examine heterogeneity across the studies. RESULTS: The combined results indicate a reduced risk of stomach cancer with intake of green tea (RR/OR=0.86, 95% CI=0.74-1.00). Subgroup analysis with six studies that reported differences between the highest and lowest consumption levels equal to or greater than five cups/day revealed a statistically significant protective effect (RR/OR=0.68, 95% CI=0.53-0.87). CONCLUSION: Green tea appears to play a protective role against the development of stomach cancer. The results also suggest that a higher level of green tea consumption might be needed for a clear preventive effect to appear. This conclusion, however, should be interpreted with caution because various biases can affect the results of a meta-analysis.

Prevalence of Otolaryngologic Diseases in South Korea: Data from the Korea National Health and Nutrition Examination Survey 2008

OBJECTIVES: The aims of this study were to evaluate the prevalence of otolaryngologic diseases in Korea. METHODS: We obtained data from the 2008 Korea National Health and Nutrition Examination Surveys (KNHANES), which were cross-sectional surveys of the civilian, non-institutionalized population of South Korea (n=4,930). A field survey team that included an otolaryngologist, nurses, and interviewers moved with a mobile examination unit and performed otolaryngologic interviews and physical examinations. RESULTS: The prevalence of subjective hearing loss, tinnitus, preauricular fistua, tympanic membrane perforation, and cholesteatoma were 11.97%, 20.27%, 2.08%, 1.60%, and 1.18%, respectively. Dizziness and vestibular dysfunction were common among Korean adults, since 23.33% of the participants reported symptoms of dizziness or imbalance, and the prevalence of vestibular dysfunction was 3.86%. The prevalence of nasal diseases was relatively high, as the prevalence of allergic rhinitis, chronic rhinosinusitis, and a deviated nasal septum were 28.01%, 7.12%, and 42.94%, respectively. Subjective dysphonia was found in 6.60% of the participants, and the prevalence of subjective dysphonia increased with age. CONCLUSION: This is the first nation-wide epidemiologic study to assess the prevalence of otolaryngologic diseases by both the Korean Otolaryngologic Society and the Ministry of Health and Welfare. Considering the high prevalence of otolaryngologic diseases in Korea, the results call for additional studies to better prevent and manage otolaryngologic diseases.

The Effects of Dietary Carbohydrate on Serum Triglyceride Concentrations in Korea

The relationship between dietary carbohydrate (CHO) and fasting triglyceride (TG) concentrations was examined in 2,689 men, 1,908 premenopausal women, and 966 postmenopausal women aged 20 - 69 years in the 1998-Korean Health and Nutrition Survey. The serum TG concentrations in fasting blood samples were measured and dietary CHO intake was assessed by using 24-hour recall method. As CHO intake increased, the TG concentrations were significantly affected (127.4 mg/dl, 132.4 mg/dl, 134.8 mg/dl, 142.6 mg/dl, 147.2 mg/dl) in postmenopausal women, while CHO intake was not significantly associated with TG concentrations in men and in premenopausal women. For the lowest to the highest quintiles of CHO, the mean TG concentrations were 120.0 mg/dl and 140.3 mg/dl in postmenopausal women with body mass index (BMI) or = 25 kg/m2. In multivariate analysis, BMI, waist hip ratio (WHR), glucose, smoking, and drinking habit were associated with serum TG concentrations in men. In premenopausal women, BMI, WHR, and glucose levels were associated with serum TG concentrations, while age, BMI, WHR, glucose levels, and CHO intake were associated with serum TG concentrations in postmenopausal women. In conclusion, CHO intake is related to serum TG concentrations in postmenopausal women in Korea.

A Case-Control Study on Dietary Quality and Risk for Coronary Heart Disease in Korean Men

OBJECTIVE: The purpose of this study was to investigate the association between dietary quality and the risk of coronary heart disease (CBD) among Korean men by a case-control study. METHODS: The cases were 108 male patients with a first acute myocardial infarction or a new diagnosis of angina pectoris who were admitted to a university teaching hospital in Seoul. Controls were 142 age-matched patients admitted to the departments of ophthalmology and orthopedic surgery at the same hospital. Dietary information was assessed by a nutritionist using a semiquantitative food frequency questionnaire (FFQ), and dietary quality index (DQI) scores were calculated. RESULTS: The intakes of total fat and cholesterol and body mass index (BMI) in cases were significantly higher than those in controls. The mean DQI scores were 8.6 for the cases and 9.4 for the controls. A higher DQI, which was indicative of a better quality diet, was inversely associated with the risk of CHD when comparing the highest to lowest quatiles, but borderline significant (odd ratios 0.60, 95% confidence interval 0.25-1.39, P for trend=0.05). CONCLUSIONS: Our findings suggest that better dietary quality may reduce the risk of CHD among Korean men.

A Study on Validity of a Semi-Quantitative Food Frequency Questionnaire for Korean Adults / 대한지역사회영양학회지

This study was conducted to validate the semi-quantitative food frequency questionnaire that was developed to assess the intakes of fatty acids, as well as energy, carbohydrates, fat, protein, minerals and vitamins in Korean adults. The validity of the semi-quantitative food frequency questionnaire was tested on 78 subjects (31 men, 47 women) aged 34 to 66 years. The semi-quantitative food frequency questionnaire included 93 food items and was validated on two 3-day dietary records. The mean intakes and the Spearman Correlation Coefficients between the semi-quantitative food frequency questionnaire and the two 3-day dietary records were analyzed for each nutrient and food group level. The mean nutrient intakes obtained from the semi-quantitative food frequency questionnaire were estimated to be greater than those of the two 3-day dietary records. The Spearman Correlation Coefficients between the energy-adjusted nutrient intakes from the semi-quantitative food frequency questionnaire and the two 3-day dietary records ranged from 0.24 for polyunsaturated fatty acids to 0.55 for fat in men and from 0.29 for polyunsaturated fatty acids to 0.55 for saturated fatty acids in women, respectively. The Spearman Correlation Coefficients for food intake ranged from 0.11 for teas and beverages to 0.58 for grains and their products in men, -0.04 for potatoes and starches to 0.73 for milk and dairy products in women. Foods consumed regularly had lower intra-person variation and tended to have higher observed correlation coefficients. These results indicate that the semi-quantitative food frequency questionnaire is a useful tool for estimating nutrient intakes, particularly of total fat and saturated fatty acid intakes.

A Case-Control Study on Risk Factors of CHD: Vegetable consumption and risk for CHD in Korean men / 한국역학회지

The purpose of this study was to investigate the association of vegetable consumption with the incidence of CHD in Korean men by a case-control study. The case group consisted of 108 patients with EKG-confirmed myocardial infarct or angiographically-confirmed(>or=50% stenosis) angina pectoris admitted to a university teaching hospital in Seoul, Korea. Controls were 142 age-matched patients admitted to the departments of ophthalmology and orthopedic surgery at the same hospital. Dietary intake was assessed by a nutritionist using a semiquantitative food frequency method, while body mass index (BMI), tobacco use, and past history of cardiovascular disease were determined during an interview and examination. The consumption of vegetables was classified by the average frequency of intake(less than 3 times/week, 3~4 times/week, 5~6 times/week, more than once/day). The percentage of subjects who consumed vegetables less than 3 times per week was 29.6% for cases and 17.6% for controls; while men who consumed vegetavle more than once per day were 16.7% for cases and 32.4% for controls. After the adjustment for age, body mass index, and tobacco use, the odds ratio of men who consumed vegetables at least once per day was 0.38(95% confidence interval, 0.18-0.85) compared with men who consumed vegetables less than three times per week. These results suggested that in a population with a relatively low fat intake, consumption of vegetables at least once per day may reduce the risk of CHD in men.

Changes in blood pressure and determinants of blood pressure level and change in Korean adolescents / 예방의학회지

Many studies have led to the notion that essential hypertension in adults is the result of a process that starts early in life: investigation of blood pressure(BP) in children and adolescents can therefore contribute to knowledge of the etiology of the condition. a A unique longitudinal study on BP in Korea, known as Kangwha Children's Blood Pressure(KCBP) Study was initiated in 1986 to investigate changes in BP in children. This study is a part of the KCBP study. The purposes of this study are to show changes in BP and to determine factors affecting to BP level and change in Korean adolescents during age period 12 to 16 years. A total of 710 students(335 males, 375 females) who were in the first grade at junior high school(12 years old) in 1992 in Kangwha County, Korea have been followed to measure BP and related factors(anthropometric, serologic and dietary factors) annually up to 1996. A total of 562 students(242 males, 320 females) completed all five annual examinations. The main results are as follows: 1. For males, mean systolic diastolic BP at age 12 and 16 years old were 108.7 mmHg & 118.1 mmHg(systolic), and 69.5 mmHg & 73.4 mmHg(diastolic), respectively. BP level was the highest when students were at 15 years old. For females, mean systolic and diastolic BP at age 12 and 16 years were 114.4 mmHg & 113.5 mmHg(systolic) and 75.2 mmHg & 72.1 mmHg(diastolic), respectively. BP level reached the highest point when they were 13-14 years old. 2. Anthropometric variables(height, weight and body mass index etc) increased consitantly during the study period for males. However, the rate of increase was decreased for females after age 15 years. Serum total cholesterol decreased and triglyceride increased according to age for males, but they did not show any significant trend for females. Total fat intake increased at age 16 years compared with that at age 14 years. Composition of carbohydrate, protein and fat among total energy intake was 65:15:20 at age 14 and 16 years. 3. Most of anthropometric measures, especially, height, body mass index(BMI) and triceps skinfold thickness, showed a significant correlation with BP level in both sexes. When BMI was adjusted, serum total cholesterol showed a significant negative correlation with systolic BP at age 12 years in males, but at age 14 years the direction of correlation changed to positive. In females serum total cholesterol was negatively correlated with diastolic BP at age 15 and 16 years. Triglyceride and creatine showed positive correlation with systolic and diastolic BP in males, but they did not show any correlation in females. There was no consistent findings between nutrient intake and BP level. However, protein intake correlated positively with diastolic BP level in males. 4. Blood pressure change was positively associated with changes in BMI and serum total cholesterol in both sexes. Change in creatine was associated with BP change positively in males and negatively in females. Students whose sodium intake was high showed higher systolic and diastolic BP in males, and students whose total fat intake was high maintained lower level of BP in females. The major determinants on BP change was BMI in both sexes.