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This study evaluated an oscillometric device (OD), Microlife WatchBP Office AFIB, and a hybrid manual auscultatory device (AD), Greenlight 300TM, to determine a suitable blood pressure (BP) measurement device for the Korea National Health and Nutrition Examination Survey in a mercury-free context. Adhering to the 2018 Universal Standard's suggested consensus, the study involved 800 subjects (mean age 51.2 ± 17.5 years; 44.3% male), who underwent triplicate BP measurements following 5 min of rest in a randomized order (OD-first: 398 participants; AD-first: 402 participants). BP difference was calculated as OD value minus AD value, with results stratified by measurement sequence. The overall BP difference and tolerable error probability were -1.1 ± 6.5/-2.6 ± 4.9 mmHg and 89.2%/92.5% for systolic/diastolic BP (SBP/DBP), respectively. Lin's concordance correlation coefficient was 0.907/0.844 for SBP/DBP (OD-first/AD-first: 0.925/0.892 for SBP, 0.842/0.845 for DBP). The overall agreement for hypertension (BP ≥ 140 and/or 90 mmHg) was 0.71 (p < 0.0001), and the OD underestimated the overall hypertension prevalence by 5.1%. Analysis of the AD-first data revealed a lower level of agreement compared to the OD-first data; however, the observed blood pressure difference adhered to Criterion 1 of the 2018 Universal Standard. Microlife met the Criterion 1 of 2018 Universal Standard but underestimated the prevalence of hypertension. The BP discrepancy increased with higher BP levels, male sex, and smaller AC. With increasing age, the discrepancy decreased for SBP and increased for DBP.

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Mercury-free sphygmomanometers are gradually replacing the traditional sphygmomanometers in clinical settings and epidemiological surveys for measuring blood pressure (BP) due to mercury toxicity. No direct comparative studies have evaluated BP differences and statistical errors of automated oscillometric devices (ODs) against electronic auscultatory devices (ADs) for epidemiologic surveys. Herein, we evaluated the validity of ODs for the Korea National Health and Nutrition Examination Survey (KNHANES) using the Universal Standard for BP device validation through a direct comparison with ADs as the reference standard. Four trained observers performed validation on 278 volunteers aged ≥ 19 years with a standardized BP measurement protocol. Agreement between the BP measurements recorded with an OD against those recorded with an AD was assessed by Lin's concordance correlation coefficient (CCC) and Bland-Altman's limits of agreement. To evaluate the agreement for BP classification, weighted kappa values were estimated. To explore the factors associated with BP measurement differences between the 2 devices, multiple linear regression analysis was performed. The average BP differences (OD-AD) were 2.6 ±â€…6.2 mm Hg for systolic BP (SBP) and -5.1 ±â€…5.6 mm Hg for diastolic BP (DBP). Lin's CCCs were 0.927 and 0.768 for the overall SBP and DBP, respectively. The cumulative percentage of absolute errors ≤10 mm Hg was 88.1% for SBP and 81.3% for DBP. The weighted kappa value for the Joint National Committee 7 BP classification was 0.75 (95% confidence interval: 0.68-0.81). An OD overestimated the prevalence of SBP (0.3%, P = .0222) and underestimated the prevalence of DBP (1.8%, P < .0001). Multivariate analysis to identify the risk factors for BP difference revealed the arm circumference (AC) to be negatively associated with BP difference. Male sex was positively associated, while age was negatively associated with SBP difference. OD-DBP was positively associated with DBP difference and negatively associated for DBP absolute error. ODs met the accuracy requirements of the Universal Standard criteria against ADs for SBP but not for DBP. Thus, the DBP values may be underestimated by ODs in the KNHANES.

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A few studies have compared auscultation and oscillometric devices with the mercury sphygmomanometer (MS) reference values for blood pressure (BP) measurement in an epidemiologic survey.Four trained observers recorded BP measurements from 766 subjects from general Korean population in 2014 and 2015. Measurements were repeated 3 times for each device, alternately using an MS and 2 electronic devices (EDs; Greenlight 300 vs Omron HEM-907), together with a randomized device sequence. The BP measurement difference was defined as BP measured by MS minus BP obtained by ED, and the absolute error as the absolute value of the difference.Mean differences in systolic BP (SBP) were -0.52 and -0.62 mmHg and those of diastolic BP (DBP) were -0.78 and 6.23 mmHg (P < .01) in the Greenlight and Omron device group, respectively. The concordance correlation coefficients were 0.97 and 0.94 for SBP and 0.95 and 0.76 for DBP in the Greenlight and Omron group, respectively (P < .05). Kappa values for the Joint National Committee 7 BP classification were 0.84 and 0.74 for Greenlight and Omron group, respectively. The prevalence of normotension, prehypertension and hypertension were 53.5%, 33.9%, and 12.5% with the MS and 59.8%, 29.0%, and 11.2% with the ED in the Omron group (P = .03, McNemar test), whereas they were insignificant in the Greenlight group.The Greenlight 300 may be a good alternative to the MS, and the Omron HEM-907 has good accuracy in SBP measurement. Due to the measurement error in DBP, Omron HEM-907 was inferior to the Greenlight device.

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The authors developed an equation to estimate 24-hour urine sodium (24HUNa) using the average of three spot urine (SU) samples (morning-first, morning, and evening) from 74 individuals and validated this equation using the average of three SU samples (morning-first, daytime, and evening) from 174 additional individuals. Compared with previously published equations using a single SU sample, the currently developed equation using the average of three SU samples showed much lower bias from measured 24HUNa (-2.9 vs >10 mmol/24 h). The intraclass and concordance correlation coefficients of the proposed equation using the average of three SU samples were 0.909 and 0.832, respectively. The limits of agreement were -64.1-58.3 mmol/24 h and approximately 100 mmol/24 h for the currently developed and previously published equations, respectively. All equations showed a tendency to overestimate or underestimate 24HUNa in a manner dependent on the level of 24HUNa but irrespective of the number of SU samples considered. Nonetheless, among the currently tested equations, our equation using the average of three SU samples provided the best estimation of 24HUNa at a population level.

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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.

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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.

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BACKGROUND: Tinnitus is a common condition and frequently can be annoying to affected individuals. We investigated the prevalence and associated factors for tinnitus in South Korea using the data from the Korea National Health and Nutrition Examination Surveys (KNHANES) during 2009-2011. METHODS: KNHANES is a cross-sectional survey of the civilian, non-institutionalized population of South Korea (n = 21 893). A field survey team that included an otolaryngologist moved with a mobile examination unit and performed interviews and physical examinations. RESULTS: Among the population over 12 years of age, the prevalence of any tinnitus was 19.7% (95% CI 18.8%-20.6%). Tinnitus was more prevalent in women, and the prevalence rate increased with age (P < 0.001). Among those with any tinnitus, 29.3% (95% CI 27.3%-31.3%) experienced annoying tinnitus that affected daily life. Annoying tinnitus also increased with age (P < 0.001), but no sex difference was demonstrated (P = 0.25). In participants aged 40 years or older, age, quality of life, depressive mood, hearing loss, feeling of dizziness, and rhinitis were associated with any tinnitus (P < 0.05). Age, hearing loss, history of cardiovascular disease, and stress were associated with annoying tinnitus (P < 0.05). CONCLUSIONS: Tinnitus is a common condition, and a large population suffers from annoying tinnitus in South Korea. Public understanding of associated factors might contribute to better management of tinnitus.

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BACKGROUND: Mortality from coronary heart disease in Korea has increased continuously, but there are few comprehensive national data on trend in the prevalence of risk factors for cardiovascular disease in this population. We examined the trends in the prevalence of major risk factors for cardiovascular disease, including smoking, obesity, hypertension, diabetes, and hypercholesterolemia, from 1998 through 2012 in a representative Korean population. METHODS: Using data from the Korea National Health and Nutrition Examination Survey I (1998) to V (2010-2012), we selected the adults aged≥30 yr who participated in both a health examination and health interview survey. RESULTS: From 1998 to 2012, significant decrease in the prevalence of hypertension was observed in both men (32.5 to 31.5%) and women (26.9 to 24.3%). Smoking rates decreased only in men (65.1 to 47.0%), whereas the prevalence of diabetes did not change over time. Conversely, the prevalence of hypercholesterolemia significantly increased from 7.2% to 12.6% for men and from 8.4% to 14.9% for women, whereas the rates of awareness and treatment for hypercholesterolemia were relatively lower than that of hypertension and diabetes. During the period, prevalence of obesity significantly increased from 26.8% to 38.1% only in men. CONCLUSIONS: The increased prevalence of hypercholesterolemia and obesity may have contributed to the increasing trend in the mortality from coronary heart disease in Korea. Further population-based surveillance of blood cholesterol levels and obesity needs to be performed, and national strategies for improvement of these factors should be established in Korea.

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BACKGROUND: Automated devices (AD) for measuring blood pressure (BP) are gradually replacing mercury sphygmomanometers (MM) in clinical settings. However, the use of ADs in epidemiological surveys has not been established. We investigated the factors associated with measurement differences when using an MM and an AD. METHODS: Two trained observers took three BP measurements in 454 subjects as part of an epidemiological survey, alternately using an MM and an AD. BP measurement difference was defined as BPMM - BPAD. Alarm reactions (ARs) were calculated by subtracting the third systolic BP (SBP) measurement from the first SBP. RESULTS: The mean age of subjects was 50.7±15.4 years (n = 454). The mean BPs using the MM and the AD were 119.8±13.9 vs. 119.5±13.6mm Hg in males and 115.0±16.8 vs. 111.6±15.7mm Hg in females for SBP and 77.7±10.4 vs. 74.7±10.4mm Hg in males and 73.2±9.3 vs. 69.9±10.3mm Hg in females for diastolic BP (DBP). Age, gender, arm circumference, and AR were the factors related to the difference. The concordance correlation coefficients for SBP and DBP were 0.8914 (95% confidence interval [CI], 0.8727-0.9102) and 0.8207 (95% CI, 0.7920-0.8494). The kappa values for the diagnosis of hypertension and Joint National Committee 7 BP classification were 0.6538 (0.5436-0.7641) and 0.5703 (0.5055-0.6351), respectively. The diagnostic sensitivity for hypertension was 59.0%. CONCLUSIONS: Age, gender, arm circumference, and AR were the factors related to the differences. Despite small differences in the mean values, the agreement and reliability were not good enough to recommend the A&D UA-767PC for adoption in epidemiological surveys of hypertension prevalence.

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The objectives of this study were to examine the trend in unhealthy food intake by socioeconomic position (SEP) and to determine whether the government's nutritional policies affect socioeconomic disparity in the food intake among adolescents. Data were from the six independent cross-sectional survey data (2006-2011) of Korea Youth Risk Behavior Web-based Survey and included 445,287 subjects aged 12-18 years. The unhealthy food intake was assessed by food frequency intake and SEP was evaluated with the family affluence scale. We observed that unhealthy food intakes decreased through the years, showing the apparent decline when nutritional policies focusing on the restriction of unhealthy foods were implemented, and the trend was all same in the different SEP groups. The pattern of unhealthy food intakes by SEP has changed before and after implementation of the policies. The intakes of carbonated beverages, fast food, and confectioneries were higher in the higher SEP group before implementation of the policies but the difference was not shown after implementation of the policies. The intake of instant noodles was consistently higher in the lower SEP group. The risk of frequent consumption of unhealthy foods was generally more decreased through the years in the higher SEP group than the lower SEP group. In conclusion, this study found the positive effect of nutritional policy on unhealthy food intake among adolescents and the high SEP group appeared to undergo greater desirable changes in dietary behaviors after implementation of nutritional policies than the low SEP group.

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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.

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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.

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OBJECTIVES: The purpose of this study was to investigate the seroprevalence of hepatitis A virus (HAV) and hepatitis E virus (HEV) in Korea during 2005. METHODS: Study subjects were selected from across Korea using a stratified multistage probability sampling design, and HAV and HEV seroprevalence was compared on the basis of sex, age, and residency. A total of 497 rural and urban people aged 10-99 years of age (mean ± SD age = 28.87 ± 17.63 years) were selected by two-stage cluster sampling and tested serologically for anti-HAV and anti-HEV IgG using an enzyme-linked immunosorbent assay. RESULTS: Among this population, the overall seroprevalence of HAV was 63.80% (55.21% aged in their 20s and 95.92% in their 30s, p < 0.01) and that of HEV was 9.40% (5.21% aged in their 20s and 7.14% in their 30s, p < 0.01). Seroprevalence also varied according to area of residence. HEV prevalence in rural areas was higher than that of urban regions based on the anti-HEV antibody, odds ratio 3.22 (95% confidence interval: 1.46-7.10, p < 0.01). There were no significant differences between male and female against anti-HAV/HEV antibodies. CONCLUSION: Our study suggested that the seropositive rates of HAV and HEV might be related to age and environmental conditions.

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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.

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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.

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OBJECTIVE: Epidemiological data on the relationship between vitamin C intake and ischemic heart disease (IHD) risk are limited in the Asian population, with a high prevalence of smoking. This study aims to investigate the association between vitamin C intake and the incidence of non-fatal IHD in Korean men. METHODS: The case group consisted of 108 patients with electrocardiogram-confirmed myocardial infarction or angiographically confirmed (>or=50% stenosis) coronary artery disease (CAD) who were admitted to a university teaching hospital in Seoul, Korea. The controls were 142 age-matched patients admitted to the departments of ophthalmology and orthopedic surgery at the same hospital. Vitamin C intake was assessed by a nutritionist using a semi-quantitative food frequency method, and body mass index (BMI), tobacco use and past history of cardiovascular disease were determined by examination and interview. RESULTS: After controlling for cardiovascular risk factors, including BMI, smoking, past history of hypertension, past history of hyperlipidemia, dietary intakes of energy, total fat (or subtype of fat), cholesterol, beta-carotene, and vitamin E, the odds ratio (OR) of non-fatal IHD was 0.34 (95% confidence interval (CI) 0.13-0.90) in the highest tertile of vitamin C intake compared with those in the lowest tertile. In a subgroup analysis, which compared nonsmokers in the highest tertile of vitamin C intake to current smokers in the lowest tertile of vitamin C intake, the odds ratio of developing non-fatal IHD was 0.12 (95% CI 0.02-0.77). CONCLUSION: This study suggests that higher intake of vitamin C is associated with the decreased risk of non-fatal IHD in a population with a high prevalence of smoking.

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OBJECTIVE: This study was performed to examine the relationship between dietary cholesterol intake and coronary artery calcification (CAC) score in healthy men. METHODS: Electron beam computed tomography (EBCT) was used to examine the CAC score in 135 Korean men aged 40-81 years who did not have clinical illness. Dietary cholesterol intake was assessed by a nutritionist using a semiquantitative food frequency method. Body mass index (BMI), serum lipid levels, cigarette use, alcohol intake, exercise, and a past history of cardiovascular disease were determined during interview and examination. RESULTS: The resultant median CAC score among those who experienced CAC was 22.5 (1-697) and average intakes of total fat and cholesterol were 22.4% (13.8-40.7) of total energy intake and 306.0 mg/day (84-1191). When the participants were classified into high (> or = 75 percentile) and low (< 75 percentile) CAC score groups, multiple logistic analysis showed that the cholesterol intake (per 10 mg/1000 kcal of energy) was significantly related to a high CAC score (OR 1.12: 95% CI 1.02-1.24), after adjustment for age, BMI, serum triglyceride level, past history of hypertension, past history of hyperlipidaemia, and energy intake. Also, when participants were classified into 2 groups (CAC score > or = 100 vs. < 100), cholesterol intake was found to be significantly related to CAC score. However, fatty acid intakes were not significantly related to the CAC score. CONCLUSION: These results suggest that in a population with a relatively low risk of coronary heart disease, higher cholesterol intake may increase the level of CAC.

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