Kyungdo Han

Low Serum 25-Hydroxyvitamin D Is Associated With Myopia in Korean Adolescents

Purposes: To assess the relationship between serum level of 25-hydroxyvitamin D (25(OH)D) and refractive error in Korean adolescents. Methods: A total of 2,038 adolescent aged 13-18 years, who participated in the Korea National Health and Nutrition Examination Survey (KNHANES) from 2008 to 2011 underwent refractive examination using an autorefractor. Serum 25(OH)D concentration and other potential risk factors were examined. Multivariate regression analysis was performed to investigate the association between serum 25(OH)D and spherical equivalent (SE). Results: Among the participants, 80.1% had myopia (-0.5 D or more myopic) and 8.9% had high myopia (-6.0D or more myopia). The age-adjusted distribution of SE according to serum 25(OH)D concentration showed a positive relationship (r = 0.067, P = 0.012).The myopia group had a significant positive relationship between SE and serum 25(OH)D tertile concentration (P = 0.020), whereas the non-myopia group did not have any significant relationship (P = 0.599).In multiple linear regression analyses, SE was significantly associated with low serum 25(OH)D concentration after adjustment for area of residence, parental income, total energy intake, dietary Ca intake, milk consumption and smoking experience (P=0.047). The prevalence of high myopia was significantly associated with the lowest tertile of serum 25(OH)D concentration after adjustment for the confounding factors (P=0.017). Smoking experience showed inverse associations with both SE and the prevalence of high myopia (P = 0.001 and 0.036) Conclusions: Low serum 25(OH)D concentration was associated with myopia prevalence in Korean adolescents. This relationship was particularly notable in adolescents with high myopia.

Sarcopenia as a Determinant of Blood Pressure in Older Koreans: Findings from the Korea National Health and Nutrition Examination Surveys (KNHANES) 2008–2010

Background Blood pressure (BP) is directly and causally associated with body size in the general population. Whether muscle mass is an important factor that determines BP remains unclear. Objective To investigate whether sarcopenia is associated with hypertension in older Koreans. Participants We surveyed 2,099 males and 2,747 females aged 60 years or older. Measurements Sarcopenia was defined as an appendicular skeletal muscle mass divided by body weight (ASM/Wt) that was <1 SD below the gender-specific mean for young adults. Obesity was defined as a body mass index (BMI) ≥25 kg/m2. Subjects were divided into four groups based on presence or absence of obesity or sarcopenia. Hypertension was defined as a systolic BP (SBP) ≥140 mmHg, a diastolic BP (DBP) ≥90 mmHg, or a self-reported current use of antihypertensive medications. Results The overall prevalence of hypertension in the four groups was as follows 49.7% for non-obese non-sarcopenia, 60.9% for non-obese sarcopenia, 66.2% for obese non-sarcopenia and 74.7% for obese sarcopenia. After adjustment for age, gender, regular activity, current smoking and alcohol use, the odds ratio (OR) for having hypertension was 1.5 (95% confidence interval (CI) = 1.23–1.84) in subjects in the non-obese sarcopenia group, 2.08 (95% CI = 1.68–2.57) in the obese non-sarcopenia group and 3.0 (95% CI = 2.48–3.63) in the obese sarcopenia group, compared with the non-obese non-sarcopenia group (p for trend <0.001). Controlling further for body weight and waist circumference did not change the association between hypertension and sarcopenia. The association between sarcopenia and hypertension was more robust in the subjects with diabetes mellitus. Conclusion Body composition beyond BMI has a considerable impact on hypertension in elderly Koreans. Subjects with sarcopenic obesity appear to have a greater risk of hypertension than simply obese or sarcopenia subjects.

Prevalence and Determinants of Diabetic Nephropathy in Korea: Korea National Health and Nutrition Examination Survey

Background Diabetic nephropathy is a leading cause of end stage renal disease and is associated with an increased risk of cardiovascular mortality. It manifests as albuminuria or impaired glomerular filtration rate (GFR), and the prevalence of diabetic nephropathy varies with ethnicity. The prevalence of diabetic nephropathy and its determinants in Korean adults have not previously been studied at the national level. This cross-sectional study was undertaken to ascertain the prevalence and determinants of albuminuria and chronic kidney disease (CKD) in Korean patients with diabetes. Methods The Korea National Health and Nutrition Examination Survey (KNHANES) V, conducted in 2011, was used to define albuminuria (n=4,652), and the dataset of KNHANES IV-V (2008-2011) was used to define CKD (n=21,521). Selected samples were weighted to represent the entire civilian population in Korea. Albuminuria was defined as a spot urine albumin/creatinine ratio >30 mg/g. CKD was defined as a GFR <60 mL/min/1.73 m2. Results Among subjects with diabetes, 26.7% had albuminuria, and 8.6% had CKD. Diabetes was associated with an approximate 2.5-fold increased risk of albuminuria, with virtually no difference between new-onset and previously diagnosed diabetes. Only systolic blood pressure was significantly associated with albuminuria, and old age, high serum triglyceride levels, and previous cardiovascular disease (CVD) were related with CKD in subjects with diabetes. Conclusion Korean subjects with diabetes had a higher prevalence of albuminuria and CKD than those without diabetes. Blood pressure was associated with albuminuria, and age, triglyceride level, and previous CVD were independent determinants of CKD in subjects with diabetes.

Normal weight obesity in Korean adults

A better way to define obesity is in terms of the percentage of body fat (BF). Subjects with normal weight, but excess BF are vulnerable to cardiovascular diseases.

Underweight is a risk factor for atrial fibrillation: A nationwide population-based study

BACKGROUND Obesity is a well-known risk factor for development of atrial fibrillation (AF). However, the impact of underweight on AF has not been previously recognized. We sought to determine the risk of AF in subjects with underweight in this study. METHODS We analyzed clinical data from a total of 132,063 individuals with the age of 40years or older who received health care checkups arranged by the national insurance program between 2003 and 2004. Newly diagnosed nonvalvular AF was identified using claim data during a median follow-up duration of 9.0years. RESULTS The mean body mass index (BMI) of patients was 23.9kg/m(2), and 3,323 individuals (2.5%) were classified as being underweight (BMI <18.5kg/m(2)). During the study period, 3,237 individuals (2.5%) developed AF. There was a U-shaped relationship between BMI and AF occurrence: Each 1.0kg/m(2) increase of BMI above 20kg/m(2) was associated with a 6% increased risk of AF (p<0.001), while each 1.0kg/m(2) lower BMI below 20kg/m(2) was associated with a 13% increased risk of AF (p<0.001) after multivariable adjustment. Underweight was significantly associated with 23% increased risk of AF, while obesity classes I and II were with 26% and 120% increased risk of AF, respectively. Excess risk of AF in the underweight was independent of thyroid disease, chronic lung disease, or history of malignancy, and was not attributable to cigarette smoking, low socioeconomic status, excessive physical activity, or heavy alcohol consumption. CONCLUSION BMI has a U-shaped relationship with the risk of AF. Underweight was an independent risk factor for AF independent of confounding factors such as chronic lung disease and malignancy. These findings suggest that underweight is associated with biological effects that contribute to the development of AF.

Identifying subgroups of obesity using the product of triglycerides and glucose: the Korea National Health and Nutrition Examination Survey, 2008–2010

To determine whether the TyG index, a product of the levels of triglycerides and glucose, may be a valuable marker for identifying metabolically obese but normal weight (MONW) or metabolically healthy but obese (MHO) individuals.

Data Analytic Process of a Nationwide Population-Based Study Using National Health Information Database Established by National Health Insurance Service.

In 2014, the National Health Insurance Service (NHIS) signed a memorandum of understanding with the Korean Diabetes Association to provide limited open access to its databases for investigating the past and current status of diabetes and its management. NHIS databases include the entire Korean population; therefore, it can be used as a population-based nationwide study for various diseases, including diabetes and its complications. This report presents how we established the analytic system of nation-wide population-based studies using the NHIS database as follows: the selection of database study population and its distribution and operational definition of diabetes and patients of currently ongoing collaboration projects.

Association Between Alcohol Consumption and Periodontal Disease: The 2008 to 2010 Korea National Health and Nutrition Examination Survey

BACKGROUND A positive association has been reported between alcohol and periodontal disease. Therefore, this study is conducted to assess the relationship between alcohol intake and severity of periodontal disease in a large probability sample of the Korean population using the Korea National Health and Nutrition Examination Survey (KNHANES). METHODS Data from KNHANES, conducted between 2008 and 2010 by the Division of Chronic Disease Surveillance under the Korea Centers for Disease Control and Prevention and the Korean Ministry of Health and Welfare, were used for this study. The presence of periodontal treatment needs according to demographic variables and anthropometric and hematologic characteristics of the participants are presented as means with their standard errors. Multivariate logistic regression analyses were used to assess the associations of periodontal treatment needs with the amount of alcohol intake and other variables including smoking and the number of times of toothbrushing per day. RESULTS An association between drinking alcohol and periodontal treatment needs could be seen in men after adjustment for variables. Adjusted odds ratios (ORs) and their 95% confidence intervals (CIs) in males were 1.271 (1.030 to 1.568) for heavy drinkers after controlling for age, smoking, body mass index, exercise, education, income, white blood cell count, diabetes, hypertension, metabolic syndrome, and number of toothbrushing episodes per day (model 3). Adjusted ORs and their 95% CIs in males were 1.569 (1.284 to 1.916) for alcohol use disorders identification test (AUDIT) level ≥20 in model 3. ORs increased with the increase in alcohol consumption levels and AUDIT levels. Statistically significant correlations between drinking and periodontal treatment needs could not be seen in female heavy drinkers or female drinkers with AUDIT levels ≥20. CONCLUSIONS Men with higher alcohol intake were more likely to have a higher prevalence of treatment needs regardless of their age, socioeconomic factors, systemic conditions (including diabetes, hypertension, and metabolic syndrome), and number of times of toothbrushing per day in multivariable adjusted models. By contrast, in women, alcohol intake was not independently associated with periodontal treatment needs. Alcohol consumption was discovered to be a potential risk indicator for periodontal treatment needs in men in this study.

Performance limitation of hybrid WDM systems due to stimulated Raman scattering

We report on the effect of stimulated Raman scattering (SRS) on the hybrid wavelength-division-multiplexing (WDM) system. The stimulated Raman scattering-induced crosstalk was measured by using a two-channel hybrid WDM system and compared with the theoretically calculated values. Using this result, we estimated the maximum number of WDM digital channels that a hybrid WDM system could support.

Inverse Relationship Between High Blood 25-Hydroxyvitamin D and Late Stage of Age-Related Macular Degeneration in a Representative Korean Population

PURPOSE To investigate the association of 25-hydroxyvitamin D with AMD. METHODS A population-based, cross-sectional study using a nationwide, systemic-stratified, multistage-clustered sampling method involved a total of 17,045 subjects older than 40 years who participated in the Korean National Health and Nutrition Examination Survey 2008 to 2012. All participants underwent standardized interviews, evaluation of blood 25-hydroxyvitamin D levels, and comprehensive ophthalmic examinations. A 45° digital fundus photograph of both eyes was taken under physiologic mydriasis. All fundus photographs were graded using the international classification and grading system. RESULTS Blood 25-hydroxyvitamin D levels were 17.5 ng/mL in women and 20.0 ng/mL in men. After adjusting for potential confounders including age, sex, smoking status, hypertension, heart problems, stroke, and sunlight-exposure time, the odds ratio (OR) for late AMD significantly decreased in the highest blood 25-hydroxyvitamin D quintile (OR, 0.32; 95% confidence interval [CI], 0.12-0.81; P for trend = 0.018) compared with the lowest quintile in men, but not in women. Early AMD was not associated with blood 25-hydroxyvitamin D levels in either sex. CONCLUSIONS High level of blood 25-hydroxyvitamin D was inversely associated with late AMD in men but not women. Considering antiangiogenic and antifibrotic action of vitamin D, association between two variables warrants further studies.