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Papers by Chung Nam

Research paper thumbnail of Additional file 1: of The effect of continuity of care on the incidence of end-stage renal disease in patients with newly detected type 2 diabetic nephropathy: a retrospective cohort study

Table S1. Sensitivity analysis of the association between continuity of care and ESRD incidence (... more Table S1. Sensitivity analysis of the association between continuity of care and ESRD incidence (including deaths). (DOC 31 kb)

Research paper thumbnail of Additional file 1: Table S1. of Disparities in socioeconomic status and neighborhood characteristics affect all-cause mortality in patients with newly diagnosed hypertension in Korea: a nationwide cohort study, 2002â 2013

The hypertensive status of subject according to individual household income. (DOCX 15 kb)

Research paper thumbnail of Incident Hepatocellular Carcinoma Risk in Patients Treated with a Sulfonylurea: A Nationwide, Nested, Case-Control Study

Scientific Reports, 2019

Several studies have shown that the use of sulfonylureas in patients with type 2 diabetes mellitu... more Several studies have shown that the use of sulfonylureas in patients with type 2 diabetes mellitus (T2DM) is associated with a higher risk of hepatocellular carcinoma (HCC). In this study, we investigated the effects of individual sulfonylureas on HCC development using the National Health Insurance Service-National Sample Cohort in South Korea. Among 47,738 subjects aged 40 years or older who had newly diagnosed with diabetes, 241 incident HCC cases and 1205 matched controls were identified. Adjusted odds ratios (ORs) as estimates of the relative risk of HCC were calculated using logistic regression analysis. Compared to patients never treated with a sulfonylurea, those treated with a sulfonylurea had a 1.7-fold increased risk of HCC development. Of the different types of sulfonylureas, the exclusive use of glimepiride was associated with a significantly elevated risk of HCC (OR = 1.89, 95% CI = 1.02–3.47) compared to those who were never treated with sulfonylureas. No significant a...

Research paper thumbnail of The effect of continuity of care on the incidence of end-stage renal disease in patients with newly detected type 2 diabetic nephropathy: a retrospective cohort study

BMC Nephrology, 2018

Background: Diabetic nephropathy requires periodic monitoring, dietary modification, and early in... more Background: Diabetic nephropathy requires periodic monitoring, dietary modification, and early intervention to prevent the disease severity within limited resource settings. To emphasize the importance of continuous care for chronic diseases, various studies have focused on the association between continuity of care (COC) and common adverse outcomes. However, studies aimed at understanding the effect of COC on the incidence of chronic diseases, such as end-stage renal disease (ESRD), are few. The aim of this study was to determine whether there is an association between COC and the incidence of ESRD among patients with diabetic nephropathy. Moreover, we identified individual-and hospital-level factors associated with the incidence of ESRD among diabetic nephropathy patients. Methods: We conducted a retrospective cohort study using the administrative National Health Insurance claims data from 2005 to 2012 in the Republic of Korea. The dependent variable, a binary variable, was the incidence of ESRD due to diabetic renal complication. In addition, using the COC index as a binary variable with a cutoff point of 0.75, we divided patients into a 'Good COC group' (COC index≥0.75) and a 'Bad COC group' (COC index< 0.75). The survival analysis was performed using the Cox proportional hazards models. Results: Among 3565 diabetic renal complication patients, ESRD occurred among 83 diabetes mellitus patients (2.3%). Nephropathy patients with lower COC level (< 0.75) had 1.99 times higher risk of ESRD incidence (95% confidence interval [CI]:1.27-3.12). In addition, the lowest income level patients had higher hazard ratio (HR) of ESRD than the highest income level patients (HR: 1.69 95% CI: 0.95-2.98), while patients with disabilities had 2.70 higher HR of ESRD than patients without disabilities (95% CI: 0.64-43). Conclusions: Among patients with diabetic renal complication, higher continuity of care was associated with lower risk of ESRD. It is therefore recommended that continuous follow-up be encouraged to prevent ESRD among diabetic renal complication patients. Moreover, disparities in health outcomes between socially vulnerable groups including patients with disabilities and those in the lowest income level should be addressed.

Research paper thumbnail of Deep Learning Algorithms with Demographic Information Help to Detect Tuberculosis in Chest Radiographs in Annual Workers’ Health Examination Data

International Journal of Environmental Research and Public Health, 2019

We aimed to use deep learning to detect tuberculosis in chest radiographs in annual workers’ heal... more We aimed to use deep learning to detect tuberculosis in chest radiographs in annual workers’ health examination data and compare the performances of convolutional neural networks (CNNs) based on images only (I-CNN) and CNNs including demographic variables (D-CNN). The I-CNN and D-CNN models were trained on 1000 chest X-ray images, both positive and negative, for tuberculosis. Feature extraction was conducted using VGG19, InceptionV3, ResNet50, DenseNet121, and InceptionResNetV2. Age, weight, height, and gender were recorded as demographic variables. The area under the receiver operating characteristic (ROC) curve (AUC) was calculated for model comparison. The AUC values of the D-CNN models were greater than that of I-CNN. The AUC values for VGG19 increased by 0.0144 (0.957 to 0.9714) in the training set, and by 0.0138 (0.9075 to 0.9213) in the test set (both p < 0.05). The D-CNN models show greater sensitivity than I-CNN models (0.815 vs. 0.775, respectively) at the same cut-off ...

Research paper thumbnail of Disparities in socioeconomic status and neighborhood characteristics affect all-cause mortality in patients with newly diagnosed hypertension in Korea: a nationwide cohort study, 2002-2013

International journal for equity in health, Jan 8, 2016

Previous studies have shown that contextual factors and individual socioeconomic status (SES) wer... more Previous studies have shown that contextual factors and individual socioeconomic status (SES) were associated with mortality in Western developed countries. In Korea, there are few empirical studies that have evaluated the association between SES and health outcomes. We conducted cohort study to investigate the socioeconomic disparity in all-cause mortality for patients newly diagnosed with hypertension in the setting of universal health care coverage. We used stratified random sample of Korean National Health Insurance enrollees (2002-2013). We included patients newly diagnosed with hypertension (n = 28,306) from 2003-2006, who received oral medication to control their hypertension. We generated a frailty model using Cox's proportional hazard regression to assess risk factors for mortality. A total of 7,825 (27.6%) of the 28,306 eligible subjects died during the study period. Compared to high income patients from advantaged neighborhoods, the adjusted hazard ratio (HR) for high...

Research paper thumbnail of Changes in morbidity and medical care utilization after the recent economic crisis in the Republic of Korea

Bulletin of The World Health Organization, 2003

Objective To examine and quantify the impact of the recent economic crisis on morbidity and medic... more Objective To examine and quantify the impact of the recent economic crisis on morbidity and medical care utilization in the Republic of Korea. Methods 22 675 people from 6791 households and 43 682 people from 12 283 households were questioned for two nationwide surveys that took place in 1995 and 1998, respectively. A separate sample pretest-posttest design was used and we conducted χ 2 test and logistic regression analysis after controlling for the maturation effect of the morbidity and medical care utilization. Findings The morbidity rates of chronic disease and acute disease increased significantly by 27.1% and 9.5%, respectively, whereas the utilization rates of outpatient and inpatient services decreased by 15.1% and 5.2%, respectively. In particular, the pace of decline in the utilization rate of outpatient services varied depending on the type of disease: morbidity rates for mental and behavioural disorders were 13.7%; for cardiovascular disease, 7.1%; and for injury, 31.6%. Conclusion After the Republic of Korean economic crisis, the morbidity and medical care utilization rates changed significantly but the degree of change depended on the type of disease or service. The time-dependent relationship between the national economy and the morbidity and medical care utilization rates needs to be further investigated.

Research paper thumbnail of Statistical Analysis of Dependent Current Status Data with Application to Tumorigenicity Experiments

Chapman & Hall/CRC Biostatistics Series, 2012

Research paper thumbnail of Clonal evolution of multi-drug-resistant hepatitis B virus during entecavir rescue therapy

Liver international : official journal of the International Association for the Study of the Liver, Nov 14, 2015

Analyzing the mutation pattern of multi-drug resistance(MDR) is important in the treatment of chr... more Analyzing the mutation pattern of multi-drug resistance(MDR) is important in the treatment of chronic hepatitis B(CHB). In this study, the evolutionary pattern of MDR mutations was investigated in patients receiving entecavir (ETV) rescue therapy. Eight CHB patients with lamivudine(LAM)-and adefovir(ADV)-resistant mutations showing suboptimal response to ETV and to subsequent ETV-plus-ADV therapy were enrolled. The clonal evolution of the mutation pattern was investigated through direct sequencing, multiplex restriction fragment mass polymorphism(RFMP), and clonal analysis, and the utility of these methods was compared. Among 160 clones at baseline, wild-type hepatitis B virus(HBV) was present in 62(38.8%), LAM-resistant mutations in 92(57.6%), and ADV-resistant mutations in 55(34.4%). LAM-resistant mutations increased to 70.6% at the end of ETV therapy and increased to 74.4% at the 12(th) month of ETV-plus-ADV therapy. During the same time periods, ETV-resistant mutations were pres...

Research paper thumbnail of The methodology for developing the 2007 Korean growth charts and blood pressure nomogram in Korean children and adolescents

Korean Journal of Pediatrics, 2008

Research paper thumbnail of Glutathione S-transferase M1 status and breast cancer risk: a meta-analysis

Yonsei medical journal, Jan 31, 2004

It is not yet clear whether Glutathione S-transferase M1 (GSTM1) polymorphisms affect the risk of... more It is not yet clear whether Glutathione S-transferase M1 (GSTM1) polymorphisms affect the risk of breast cancer. The aim of this study is to provide a comprehensive meta-analysis of all the available, published case-control studies on the extent of the possible association between GSTM1 polymorphisms and susceptibility to breast cancer. Twenty case-control studies on GSTM1 and breast cancer were identified using both PUBMED and a manual search. Meta-analysis was conducted by the Peto method. Subgroup analyses were undertaken, in order to explore the relationship between effect sizes and the study characteristics. The overall odds ratio (OR) was found to be 1.06 (95% CI, 0.99-1.14). The OR for post-menopausal women with GSTM1 deficiency was determined to be 1.19 (95% CI, 1.05-1.34). In populations with a low frequency of GSTM1 deficiency, a greater increase was observed (OR, 1.20; 95% CI, 1.08-1.34). Furthermore, the highest associations were found in post-menopausal women with a low...

Research paper thumbnail of Dipstick urine protein, as a predictor of cardiovascular mortality in Korean men: Korea Medical Insurance Corporation study

Journal of preventive medicine and public health = Yebang Ŭihakhoe chi, 2006

This study was to investigate if the dipstick proteinuria can predict cardiovascular mortality in... more This study was to investigate if the dipstick proteinuria can predict cardiovascular mortality in a population of Korean men. We measured urine protein and other cardiovascular risk factors in 100,059 Korean men, aged between 35-59 years in 1990 and 1992. Levels of proteinuria measured by dipstick method were trace or less, 1+, 2+, and 3+ or greater. The primary outcomes were deaths from all causes, cardiovascular disease, cancer, and others in a 12 year follow-up from 1993 to 2004. The multivariate-adjusted relative risks (95% CI) for cardiovascular death according to the level of proteinuria (1+, 2+, 3+ and more) in 1990 examination were 2.18 (1.36-3.48), 2.55 (1.37-4.78), and 4.57 (2.16-9.66) respectively. The corresponding relative risks according to the level of proteinuria in 1992 examination were 2.49 (1.71-3.64), 2.64 (1.53-4.58), and 2.78 (1.15-6.73). The relative risks for cardiovascular death of men with proteinuria (1+ or greater) once and twice among the examinations we...

Research paper thumbnail of Scheduling mammography screening for the early detection of breast cancer in Korean women

Journal of medical screening, 2007

To propose an efficient screening schedule for breast cancer among Korean women using the stochas... more To propose an efficient screening schedule for breast cancer among Korean women using the stochastic model in which the age-specific incidence rate was considered. Female breast cancer data in the Korea Central Cancer Registry 2002. The stochastic model was based on the threshold method, in which the schedule is determined by a pre-specified threshold value. The threshold value was defined as the probability of being in a preclinical state of breast cancer at age 40 years. The sensitivity of the mammography was specified as 0.7. Two models for mean sojourn time (MST) in the preclinical state were considered; MSTs for Model I were 2 (ages < 50 years), 3 (ages 50-59 years), and 4 years (ages > or = 60 years), and MSTs for Model II were 3, 4, and 5 years for the corresponding age groups. The threshold method for Model I generated 19 examinations within the screening ages of 40-69 years. Each screening time was determined at ages 40.0, 41.6, 43.2, 44.8, 46.0, 47.2, 48.4, 49.6, 50....

Research paper thumbnail of Age-Specific Prostate-Specific Antigen Reference Ranges in Korean Men

Urology, 2007

The serum prostate-specific antigen (PSA) level varies widely among different races and increases... more The serum prostate-specific antigen (PSA) level varies widely among different races and increases with age. In this study, we evaluated the variation in serum PSA levels in a multicenter study population to determine a standard age-specific PSA reference range for Korean men without clinically evident prostate cancer. METHODS We retrospectively analyzed 120,439 Korean men, ranging in age from 30 to 79 years, whose serum PSA levels were measured at one of eight referral hospitals from November 1998 to July 2005. RESULTS Our recommended age-specific reference ranges (95th percentile) of serum PSA levels for Korean men were 0.32 to 1.88 ng/mL for men 30 to 39 years, 0.30 to 1.92 ng/mL for men 40 to 49 years, 0.30 to 2.37 ng/mL for men 50 to 59 years, 0.31 to 3.56 ng/mL for men 60 to 69 years, and 0.30 to 5.19 ng/mL for men 70 to 79 years old. The serum PSA level increased annually, corresponding to an increase of 0.0023 ng/mL for men in their 40s, 0.0175 ng/mL for men in their 50s, 0.0499 ng/mL for men in their 60s, and 0.0398 ng/mL for men in their 70s, with a steep increase for men in their 50s and the largest increase in men older than 60 years. CONCLUSIONS The results of our study have shown that the age-specific reference ranges (95th percentile) for serum PSA levels in Korean men are lower than those for white men. Our newly proposed age-specific reference ranges from this multicenter study will be more valuable in the interpretation of PSA data for Korean men.

Research paper thumbnail of Prediction of thrombus resolution after intravenous thrombolysis assessed by CT-based thrombus imaging

Thrombosis and Haemostasis, 2012

SummaryThe degree of thrombus resolution directly indicates the effectiveness of a thrombolytic d... more SummaryThe degree of thrombus resolution directly indicates the effectiveness of a thrombolytic drug. We investigated the degree of thrombus resolution and factors associated with thrombus resolution after intravenous (IV) recombinant tissue plasminogen activator (rt-PA) using thin-section noncontrast computed tomography (NCT). Thin-section NCTs were performed before and immediately after IV rt-PA infusion in acute stroke patients. The thrombus volume and Hounsfield unit were measured using three-dimensional imaging software. Immediate recanalisation was assessed immediately after IV rt-PA infusion using CT angiography. During a three-year study period, 130 patients were prospectively enrolled. On baseline thin-section NCT, no thrombi were found in 30 patients (23%). Among the 100 patients with confirmed thrombus, the median volume decreased by 20% on the follow-up NCT. The thrombus was completely resolved in 8%. Of note, an increase in thrombus volume was observed in 20 patients. I...

Research paper thumbnail of Clinicopathologic characteristics related to the high variability of coding mononucleotide repeat sequences in tumors with high-microsatellite instability

Oncology Reports, 2003

Frameshift mutation at coding mononucleotide repeat sequences are common in tumors with microsate... more Frameshift mutation at coding mononucleotide repeat sequences are common in tumors with microsatellite instability (MSI-H), but the incidences are different among the target genes. We analyzed the mutational profiles of 12 known target genes containing polydeoxyadenosine repeats in their coding sequences in 39 MSI-H colorectal carcinomas and 40 MSI-H gastric carcinomas by using polymerase chain reaction and sequencing, and compared the results with the clinicopathologic characteristics. Frameshift mutations of target genes in the MSI-H colorectal and gastric carcinomas are increased according to the length of the polydeoxyadenosine repeats in the target genes. The mean mutational rates of MSI-H colorectal carcinomas and MSI-H gastric carcinomas were 2.03 and 1.95 in the 4 genes containing (A)10 repeats, 1.23 and 0.73 in the 4 genes with (A)9 repeats and 0.61 and 0.48 in the 4 genes containing (A)8 repeats, respectively (p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001). Among the evaluated clinicopathologic findings, intestinal type gastric carcinomas had more frameshift mutations than the diffuse type carcinomas (3.5 vs. 1.9, p=0.01). These findings suggest that mutational rates of the target genes in MSI-H tumors are diverse, and higher mutational rates are related to the length of mononucleotide repeat sequences of the target genes and histologic type of tumors.

Research paper thumbnail of Effect of Smoking on the Paradox of High Waist-to-Hip Ratio and Low Body Mass Index

Obesity Research, 2002

JEE, SUN HA, SOON YOUNG LEE, CHUNG MO NAM, SANG YON KIM, AND MIYONG T. KIM. Effect of smoking on ... more JEE, SUN HA, SOON YOUNG LEE, CHUNG MO NAM, SANG YON KIM, AND MIYONG T. KIM. Effect of smoking on the paradox of high waist-to-hip ratio and low body mass index. Obes Res. 2002;10:891-895. Objective: Research on diabetes mellitus (DM) indicates that people with a low body mass index (BMI) but a high waistto-hip ratio (WHR) are in a particularly high-risk group. The purpose of this study was to investigate the prevalence of and the effect of smoking on this paradoxical relationship. Research Methods and Procedures: Our study sample consisted of 3450 men and 4250 women who had participated in the Korean Nationwide Health Examination Survey. We divided the study sample into tertiles (low, medium, and high), according to the level of WHR and of BMI, which yielded nine different combinations. Individuals exhibiting so-called paradox A had the highest WHR and the lowest BMI. Results: The prevalence of paradox A was 4.7% for men and 3.8% for women. The overall agreement of WHR and BMI groups was poor [for men: ϭ 0.31 and 95% confidence interval (CI) ϭ 0.29 to 0.34; for women: ϭ 0.39 and 95% CI ϭ 0.37 to 0.42 for women]. The odds ratios for subjects having paradox A were estimated using a logistic regression model after adjusting for age, age 2 , height, education, smoking, use of alcohol, and exercise. The risk for paradox A among current smokers was 2.1-fold (95% CI, 1.5 to 3.0) higher for men and 2.5-fold (95% CI, 1.6 to 3.9) higher for women than for nonsmokers, after adjusting for age and covariates. Discussion: Cigarette smoking may increase the risk of paradox A. The findings of this study should be crossvalidated to different populations.

Research paper thumbnail of Controlling the healthy worker effect in the presence of an intermediate variable

Environmetrics, 2004

The healthy worker effect is an important issue in occupational epidemiology. We propose a new st... more The healthy worker effect is an important issue in occupational epidemiology. We propose a new statistical method to test the relationship between exposure and time to death in the presence of the healthy worker effect. The basic idea of the proposed method reflects length bias sampling caused by job changes. According to simulation studies, both the proposed test and a test based on the Cox model including job changes as a time-dependent covariate seem to be satisfactory at the upper 5% significance level. However, the Cox models involving job changes as a timeindependent covariate are unsatisfactory. The proposed test is superior in power to the test based on the Cox model with time-dependent employment status.

Research paper thumbnail of Effects of constraint-induced movement therapy on neurogenesis and functional recovery after early hypoxic-ischemic injury in mice

Developmental Medicine & Child Neurology, 2011

BrdU 5-bromo-2-deoxyuridine CIMT Constraint-induced movement therapy CIMT-EE Constraint-induced m... more BrdU 5-bromo-2-deoxyuridine CIMT Constraint-induced movement therapy CIMT-EE Constraint-induced movement therapy with an enriched-environment ICH Intracerebral hemorrhage AIM Constraint-induced movement therapy (CIMT) has emerged as a promising therapeutic strategy for improving affected upper limb function in children with hemiplegic cerebral palsy (CP). However, little is known about the changes in the brain that are induced by CIMT. This study was designed to investigate these changes and behavioural performance after CIMT intervention in mice with neonatal hypoxic-ischemic brain injury. METHOD We utilized the neonatal hypoxic-ischemic brain injury model established in mice pups. Three weeks after the injury, the mice were randomly assigned to the following three groups: the control group (n=15), the enriched-environment group (n=17), and the CIMT with an enriched-environment group (CIMT-EE, n=15). 5-bromo-2-deoxyuridine (BrdU) was injected daily to label proliferating cells during the 2 weeks of intervention. RESULTS The CIMT-EE group showed better fall rate in the horizontal ladder rung walking test (mean 5.4%, SD 3.6%) than either the control (mean 14.3%, SD 7.3%; p=0.001) or enriched-environment (mean 12.4%, SD 7.7%; p=0.010) groups 2 weeks after the end of intervention. The CIMT-EE group also showed more neurogenesis (mean 7069 cells ⁄ mm 3 , SD 4017 cells ⁄ mm 3) than either the control group (mean 1555 cells ⁄ mm 3 , SD 1422 cells ⁄ mm 3 ; p<0.001) or enriched-environment group (mean 2994 cells ⁄ mm 3 , SD 3498 cells ⁄ mm 3 ; p=0.001) in the subventricular zone. In the striatum, neurogenesis in the CIMT-EE group (mean 534 cells ⁄ mm 3 , SD 441 cells ⁄ mm 3) was greater than in the control group (mean 95 cells ⁄ mm 3 , SD 133 cells ⁄ mm 3 ; p=0.001).

Research paper thumbnail of P-366 Prehypertension and Mortality from Coronary Heart Disease and Stroke: 12 years of Follow-Up in Korean Men

CVD Prevention and Control, 2009

Research paper thumbnail of Additional file 1: of The effect of continuity of care on the incidence of end-stage renal disease in patients with newly detected type 2 diabetic nephropathy: a retrospective cohort study

Table S1. Sensitivity analysis of the association between continuity of care and ESRD incidence (... more Table S1. Sensitivity analysis of the association between continuity of care and ESRD incidence (including deaths). (DOC 31 kb)

Research paper thumbnail of Additional file 1: Table S1. of Disparities in socioeconomic status and neighborhood characteristics affect all-cause mortality in patients with newly diagnosed hypertension in Korea: a nationwide cohort study, 2002â 2013

The hypertensive status of subject according to individual household income. (DOCX 15 kb)

Research paper thumbnail of Incident Hepatocellular Carcinoma Risk in Patients Treated with a Sulfonylurea: A Nationwide, Nested, Case-Control Study

Scientific Reports, 2019

Several studies have shown that the use of sulfonylureas in patients with type 2 diabetes mellitu... more Several studies have shown that the use of sulfonylureas in patients with type 2 diabetes mellitus (T2DM) is associated with a higher risk of hepatocellular carcinoma (HCC). In this study, we investigated the effects of individual sulfonylureas on HCC development using the National Health Insurance Service-National Sample Cohort in South Korea. Among 47,738 subjects aged 40 years or older who had newly diagnosed with diabetes, 241 incident HCC cases and 1205 matched controls were identified. Adjusted odds ratios (ORs) as estimates of the relative risk of HCC were calculated using logistic regression analysis. Compared to patients never treated with a sulfonylurea, those treated with a sulfonylurea had a 1.7-fold increased risk of HCC development. Of the different types of sulfonylureas, the exclusive use of glimepiride was associated with a significantly elevated risk of HCC (OR = 1.89, 95% CI = 1.02–3.47) compared to those who were never treated with sulfonylureas. No significant a...

Research paper thumbnail of The effect of continuity of care on the incidence of end-stage renal disease in patients with newly detected type 2 diabetic nephropathy: a retrospective cohort study

BMC Nephrology, 2018

Background: Diabetic nephropathy requires periodic monitoring, dietary modification, and early in... more Background: Diabetic nephropathy requires periodic monitoring, dietary modification, and early intervention to prevent the disease severity within limited resource settings. To emphasize the importance of continuous care for chronic diseases, various studies have focused on the association between continuity of care (COC) and common adverse outcomes. However, studies aimed at understanding the effect of COC on the incidence of chronic diseases, such as end-stage renal disease (ESRD), are few. The aim of this study was to determine whether there is an association between COC and the incidence of ESRD among patients with diabetic nephropathy. Moreover, we identified individual-and hospital-level factors associated with the incidence of ESRD among diabetic nephropathy patients. Methods: We conducted a retrospective cohort study using the administrative National Health Insurance claims data from 2005 to 2012 in the Republic of Korea. The dependent variable, a binary variable, was the incidence of ESRD due to diabetic renal complication. In addition, using the COC index as a binary variable with a cutoff point of 0.75, we divided patients into a 'Good COC group' (COC index≥0.75) and a 'Bad COC group' (COC index< 0.75). The survival analysis was performed using the Cox proportional hazards models. Results: Among 3565 diabetic renal complication patients, ESRD occurred among 83 diabetes mellitus patients (2.3%). Nephropathy patients with lower COC level (< 0.75) had 1.99 times higher risk of ESRD incidence (95% confidence interval [CI]:1.27-3.12). In addition, the lowest income level patients had higher hazard ratio (HR) of ESRD than the highest income level patients (HR: 1.69 95% CI: 0.95-2.98), while patients with disabilities had 2.70 higher HR of ESRD than patients without disabilities (95% CI: 0.64-43). Conclusions: Among patients with diabetic renal complication, higher continuity of care was associated with lower risk of ESRD. It is therefore recommended that continuous follow-up be encouraged to prevent ESRD among diabetic renal complication patients. Moreover, disparities in health outcomes between socially vulnerable groups including patients with disabilities and those in the lowest income level should be addressed.

Research paper thumbnail of Deep Learning Algorithms with Demographic Information Help to Detect Tuberculosis in Chest Radiographs in Annual Workers’ Health Examination Data

International Journal of Environmental Research and Public Health, 2019

We aimed to use deep learning to detect tuberculosis in chest radiographs in annual workers’ heal... more We aimed to use deep learning to detect tuberculosis in chest radiographs in annual workers’ health examination data and compare the performances of convolutional neural networks (CNNs) based on images only (I-CNN) and CNNs including demographic variables (D-CNN). The I-CNN and D-CNN models were trained on 1000 chest X-ray images, both positive and negative, for tuberculosis. Feature extraction was conducted using VGG19, InceptionV3, ResNet50, DenseNet121, and InceptionResNetV2. Age, weight, height, and gender were recorded as demographic variables. The area under the receiver operating characteristic (ROC) curve (AUC) was calculated for model comparison. The AUC values of the D-CNN models were greater than that of I-CNN. The AUC values for VGG19 increased by 0.0144 (0.957 to 0.9714) in the training set, and by 0.0138 (0.9075 to 0.9213) in the test set (both p < 0.05). The D-CNN models show greater sensitivity than I-CNN models (0.815 vs. 0.775, respectively) at the same cut-off ...

Research paper thumbnail of Disparities in socioeconomic status and neighborhood characteristics affect all-cause mortality in patients with newly diagnosed hypertension in Korea: a nationwide cohort study, 2002-2013

International journal for equity in health, Jan 8, 2016

Previous studies have shown that contextual factors and individual socioeconomic status (SES) wer... more Previous studies have shown that contextual factors and individual socioeconomic status (SES) were associated with mortality in Western developed countries. In Korea, there are few empirical studies that have evaluated the association between SES and health outcomes. We conducted cohort study to investigate the socioeconomic disparity in all-cause mortality for patients newly diagnosed with hypertension in the setting of universal health care coverage. We used stratified random sample of Korean National Health Insurance enrollees (2002-2013). We included patients newly diagnosed with hypertension (n = 28,306) from 2003-2006, who received oral medication to control their hypertension. We generated a frailty model using Cox's proportional hazard regression to assess risk factors for mortality. A total of 7,825 (27.6%) of the 28,306 eligible subjects died during the study period. Compared to high income patients from advantaged neighborhoods, the adjusted hazard ratio (HR) for high...

Research paper thumbnail of Changes in morbidity and medical care utilization after the recent economic crisis in the Republic of Korea

Bulletin of The World Health Organization, 2003

Objective To examine and quantify the impact of the recent economic crisis on morbidity and medic... more Objective To examine and quantify the impact of the recent economic crisis on morbidity and medical care utilization in the Republic of Korea. Methods 22 675 people from 6791 households and 43 682 people from 12 283 households were questioned for two nationwide surveys that took place in 1995 and 1998, respectively. A separate sample pretest-posttest design was used and we conducted χ 2 test and logistic regression analysis after controlling for the maturation effect of the morbidity and medical care utilization. Findings The morbidity rates of chronic disease and acute disease increased significantly by 27.1% and 9.5%, respectively, whereas the utilization rates of outpatient and inpatient services decreased by 15.1% and 5.2%, respectively. In particular, the pace of decline in the utilization rate of outpatient services varied depending on the type of disease: morbidity rates for mental and behavioural disorders were 13.7%; for cardiovascular disease, 7.1%; and for injury, 31.6%. Conclusion After the Republic of Korean economic crisis, the morbidity and medical care utilization rates changed significantly but the degree of change depended on the type of disease or service. The time-dependent relationship between the national economy and the morbidity and medical care utilization rates needs to be further investigated.

Research paper thumbnail of Statistical Analysis of Dependent Current Status Data with Application to Tumorigenicity Experiments

Chapman & Hall/CRC Biostatistics Series, 2012

Research paper thumbnail of Clonal evolution of multi-drug-resistant hepatitis B virus during entecavir rescue therapy

Liver international : official journal of the International Association for the Study of the Liver, Nov 14, 2015

Analyzing the mutation pattern of multi-drug resistance(MDR) is important in the treatment of chr... more Analyzing the mutation pattern of multi-drug resistance(MDR) is important in the treatment of chronic hepatitis B(CHB). In this study, the evolutionary pattern of MDR mutations was investigated in patients receiving entecavir (ETV) rescue therapy. Eight CHB patients with lamivudine(LAM)-and adefovir(ADV)-resistant mutations showing suboptimal response to ETV and to subsequent ETV-plus-ADV therapy were enrolled. The clonal evolution of the mutation pattern was investigated through direct sequencing, multiplex restriction fragment mass polymorphism(RFMP), and clonal analysis, and the utility of these methods was compared. Among 160 clones at baseline, wild-type hepatitis B virus(HBV) was present in 62(38.8%), LAM-resistant mutations in 92(57.6%), and ADV-resistant mutations in 55(34.4%). LAM-resistant mutations increased to 70.6% at the end of ETV therapy and increased to 74.4% at the 12(th) month of ETV-plus-ADV therapy. During the same time periods, ETV-resistant mutations were pres...

Research paper thumbnail of The methodology for developing the 2007 Korean growth charts and blood pressure nomogram in Korean children and adolescents

Korean Journal of Pediatrics, 2008

Research paper thumbnail of Glutathione S-transferase M1 status and breast cancer risk: a meta-analysis

Yonsei medical journal, Jan 31, 2004

It is not yet clear whether Glutathione S-transferase M1 (GSTM1) polymorphisms affect the risk of... more It is not yet clear whether Glutathione S-transferase M1 (GSTM1) polymorphisms affect the risk of breast cancer. The aim of this study is to provide a comprehensive meta-analysis of all the available, published case-control studies on the extent of the possible association between GSTM1 polymorphisms and susceptibility to breast cancer. Twenty case-control studies on GSTM1 and breast cancer were identified using both PUBMED and a manual search. Meta-analysis was conducted by the Peto method. Subgroup analyses were undertaken, in order to explore the relationship between effect sizes and the study characteristics. The overall odds ratio (OR) was found to be 1.06 (95% CI, 0.99-1.14). The OR for post-menopausal women with GSTM1 deficiency was determined to be 1.19 (95% CI, 1.05-1.34). In populations with a low frequency of GSTM1 deficiency, a greater increase was observed (OR, 1.20; 95% CI, 1.08-1.34). Furthermore, the highest associations were found in post-menopausal women with a low...

Research paper thumbnail of Dipstick urine protein, as a predictor of cardiovascular mortality in Korean men: Korea Medical Insurance Corporation study

Journal of preventive medicine and public health = Yebang Ŭihakhoe chi, 2006

This study was to investigate if the dipstick proteinuria can predict cardiovascular mortality in... more This study was to investigate if the dipstick proteinuria can predict cardiovascular mortality in a population of Korean men. We measured urine protein and other cardiovascular risk factors in 100,059 Korean men, aged between 35-59 years in 1990 and 1992. Levels of proteinuria measured by dipstick method were trace or less, 1+, 2+, and 3+ or greater. The primary outcomes were deaths from all causes, cardiovascular disease, cancer, and others in a 12 year follow-up from 1993 to 2004. The multivariate-adjusted relative risks (95% CI) for cardiovascular death according to the level of proteinuria (1+, 2+, 3+ and more) in 1990 examination were 2.18 (1.36-3.48), 2.55 (1.37-4.78), and 4.57 (2.16-9.66) respectively. The corresponding relative risks according to the level of proteinuria in 1992 examination were 2.49 (1.71-3.64), 2.64 (1.53-4.58), and 2.78 (1.15-6.73). The relative risks for cardiovascular death of men with proteinuria (1+ or greater) once and twice among the examinations we...

Research paper thumbnail of Scheduling mammography screening for the early detection of breast cancer in Korean women

Journal of medical screening, 2007

To propose an efficient screening schedule for breast cancer among Korean women using the stochas... more To propose an efficient screening schedule for breast cancer among Korean women using the stochastic model in which the age-specific incidence rate was considered. Female breast cancer data in the Korea Central Cancer Registry 2002. The stochastic model was based on the threshold method, in which the schedule is determined by a pre-specified threshold value. The threshold value was defined as the probability of being in a preclinical state of breast cancer at age 40 years. The sensitivity of the mammography was specified as 0.7. Two models for mean sojourn time (MST) in the preclinical state were considered; MSTs for Model I were 2 (ages < 50 years), 3 (ages 50-59 years), and 4 years (ages > or = 60 years), and MSTs for Model II were 3, 4, and 5 years for the corresponding age groups. The threshold method for Model I generated 19 examinations within the screening ages of 40-69 years. Each screening time was determined at ages 40.0, 41.6, 43.2, 44.8, 46.0, 47.2, 48.4, 49.6, 50....

Research paper thumbnail of Age-Specific Prostate-Specific Antigen Reference Ranges in Korean Men

Urology, 2007

The serum prostate-specific antigen (PSA) level varies widely among different races and increases... more The serum prostate-specific antigen (PSA) level varies widely among different races and increases with age. In this study, we evaluated the variation in serum PSA levels in a multicenter study population to determine a standard age-specific PSA reference range for Korean men without clinically evident prostate cancer. METHODS We retrospectively analyzed 120,439 Korean men, ranging in age from 30 to 79 years, whose serum PSA levels were measured at one of eight referral hospitals from November 1998 to July 2005. RESULTS Our recommended age-specific reference ranges (95th percentile) of serum PSA levels for Korean men were 0.32 to 1.88 ng/mL for men 30 to 39 years, 0.30 to 1.92 ng/mL for men 40 to 49 years, 0.30 to 2.37 ng/mL for men 50 to 59 years, 0.31 to 3.56 ng/mL for men 60 to 69 years, and 0.30 to 5.19 ng/mL for men 70 to 79 years old. The serum PSA level increased annually, corresponding to an increase of 0.0023 ng/mL for men in their 40s, 0.0175 ng/mL for men in their 50s, 0.0499 ng/mL for men in their 60s, and 0.0398 ng/mL for men in their 70s, with a steep increase for men in their 50s and the largest increase in men older than 60 years. CONCLUSIONS The results of our study have shown that the age-specific reference ranges (95th percentile) for serum PSA levels in Korean men are lower than those for white men. Our newly proposed age-specific reference ranges from this multicenter study will be more valuable in the interpretation of PSA data for Korean men.

Research paper thumbnail of Prediction of thrombus resolution after intravenous thrombolysis assessed by CT-based thrombus imaging

Thrombosis and Haemostasis, 2012

SummaryThe degree of thrombus resolution directly indicates the effectiveness of a thrombolytic d... more SummaryThe degree of thrombus resolution directly indicates the effectiveness of a thrombolytic drug. We investigated the degree of thrombus resolution and factors associated with thrombus resolution after intravenous (IV) recombinant tissue plasminogen activator (rt-PA) using thin-section noncontrast computed tomography (NCT). Thin-section NCTs were performed before and immediately after IV rt-PA infusion in acute stroke patients. The thrombus volume and Hounsfield unit were measured using three-dimensional imaging software. Immediate recanalisation was assessed immediately after IV rt-PA infusion using CT angiography. During a three-year study period, 130 patients were prospectively enrolled. On baseline thin-section NCT, no thrombi were found in 30 patients (23%). Among the 100 patients with confirmed thrombus, the median volume decreased by 20% on the follow-up NCT. The thrombus was completely resolved in 8%. Of note, an increase in thrombus volume was observed in 20 patients. I...

Research paper thumbnail of Clinicopathologic characteristics related to the high variability of coding mononucleotide repeat sequences in tumors with high-microsatellite instability

Oncology Reports, 2003

Frameshift mutation at coding mononucleotide repeat sequences are common in tumors with microsate... more Frameshift mutation at coding mononucleotide repeat sequences are common in tumors with microsatellite instability (MSI-H), but the incidences are different among the target genes. We analyzed the mutational profiles of 12 known target genes containing polydeoxyadenosine repeats in their coding sequences in 39 MSI-H colorectal carcinomas and 40 MSI-H gastric carcinomas by using polymerase chain reaction and sequencing, and compared the results with the clinicopathologic characteristics. Frameshift mutations of target genes in the MSI-H colorectal and gastric carcinomas are increased according to the length of the polydeoxyadenosine repeats in the target genes. The mean mutational rates of MSI-H colorectal carcinomas and MSI-H gastric carcinomas were 2.03 and 1.95 in the 4 genes containing (A)10 repeats, 1.23 and 0.73 in the 4 genes with (A)9 repeats and 0.61 and 0.48 in the 4 genes containing (A)8 repeats, respectively (p&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt;0.001). Among the evaluated clinicopathologic findings, intestinal type gastric carcinomas had more frameshift mutations than the diffuse type carcinomas (3.5 vs. 1.9, p=0.01). These findings suggest that mutational rates of the target genes in MSI-H tumors are diverse, and higher mutational rates are related to the length of mononucleotide repeat sequences of the target genes and histologic type of tumors.

Research paper thumbnail of Effect of Smoking on the Paradox of High Waist-to-Hip Ratio and Low Body Mass Index

Obesity Research, 2002

JEE, SUN HA, SOON YOUNG LEE, CHUNG MO NAM, SANG YON KIM, AND MIYONG T. KIM. Effect of smoking on ... more JEE, SUN HA, SOON YOUNG LEE, CHUNG MO NAM, SANG YON KIM, AND MIYONG T. KIM. Effect of smoking on the paradox of high waist-to-hip ratio and low body mass index. Obes Res. 2002;10:891-895. Objective: Research on diabetes mellitus (DM) indicates that people with a low body mass index (BMI) but a high waistto-hip ratio (WHR) are in a particularly high-risk group. The purpose of this study was to investigate the prevalence of and the effect of smoking on this paradoxical relationship. Research Methods and Procedures: Our study sample consisted of 3450 men and 4250 women who had participated in the Korean Nationwide Health Examination Survey. We divided the study sample into tertiles (low, medium, and high), according to the level of WHR and of BMI, which yielded nine different combinations. Individuals exhibiting so-called paradox A had the highest WHR and the lowest BMI. Results: The prevalence of paradox A was 4.7% for men and 3.8% for women. The overall agreement of WHR and BMI groups was poor [for men: ϭ 0.31 and 95% confidence interval (CI) ϭ 0.29 to 0.34; for women: ϭ 0.39 and 95% CI ϭ 0.37 to 0.42 for women]. The odds ratios for subjects having paradox A were estimated using a logistic regression model after adjusting for age, age 2 , height, education, smoking, use of alcohol, and exercise. The risk for paradox A among current smokers was 2.1-fold (95% CI, 1.5 to 3.0) higher for men and 2.5-fold (95% CI, 1.6 to 3.9) higher for women than for nonsmokers, after adjusting for age and covariates. Discussion: Cigarette smoking may increase the risk of paradox A. The findings of this study should be crossvalidated to different populations.

Research paper thumbnail of Controlling the healthy worker effect in the presence of an intermediate variable

Environmetrics, 2004

The healthy worker effect is an important issue in occupational epidemiology. We propose a new st... more The healthy worker effect is an important issue in occupational epidemiology. We propose a new statistical method to test the relationship between exposure and time to death in the presence of the healthy worker effect. The basic idea of the proposed method reflects length bias sampling caused by job changes. According to simulation studies, both the proposed test and a test based on the Cox model including job changes as a time-dependent covariate seem to be satisfactory at the upper 5% significance level. However, the Cox models involving job changes as a timeindependent covariate are unsatisfactory. The proposed test is superior in power to the test based on the Cox model with time-dependent employment status.

Research paper thumbnail of Effects of constraint-induced movement therapy on neurogenesis and functional recovery after early hypoxic-ischemic injury in mice

Developmental Medicine & Child Neurology, 2011

BrdU 5-bromo-2-deoxyuridine CIMT Constraint-induced movement therapy CIMT-EE Constraint-induced m... more BrdU 5-bromo-2-deoxyuridine CIMT Constraint-induced movement therapy CIMT-EE Constraint-induced movement therapy with an enriched-environment ICH Intracerebral hemorrhage AIM Constraint-induced movement therapy (CIMT) has emerged as a promising therapeutic strategy for improving affected upper limb function in children with hemiplegic cerebral palsy (CP). However, little is known about the changes in the brain that are induced by CIMT. This study was designed to investigate these changes and behavioural performance after CIMT intervention in mice with neonatal hypoxic-ischemic brain injury. METHOD We utilized the neonatal hypoxic-ischemic brain injury model established in mice pups. Three weeks after the injury, the mice were randomly assigned to the following three groups: the control group (n=15), the enriched-environment group (n=17), and the CIMT with an enriched-environment group (CIMT-EE, n=15). 5-bromo-2-deoxyuridine (BrdU) was injected daily to label proliferating cells during the 2 weeks of intervention. RESULTS The CIMT-EE group showed better fall rate in the horizontal ladder rung walking test (mean 5.4%, SD 3.6%) than either the control (mean 14.3%, SD 7.3%; p=0.001) or enriched-environment (mean 12.4%, SD 7.7%; p=0.010) groups 2 weeks after the end of intervention. The CIMT-EE group also showed more neurogenesis (mean 7069 cells ⁄ mm 3 , SD 4017 cells ⁄ mm 3) than either the control group (mean 1555 cells ⁄ mm 3 , SD 1422 cells ⁄ mm 3 ; p<0.001) or enriched-environment group (mean 2994 cells ⁄ mm 3 , SD 3498 cells ⁄ mm 3 ; p=0.001) in the subventricular zone. In the striatum, neurogenesis in the CIMT-EE group (mean 534 cells ⁄ mm 3 , SD 441 cells ⁄ mm 3) was greater than in the control group (mean 95 cells ⁄ mm 3 , SD 133 cells ⁄ mm 3 ; p=0.001).

Research paper thumbnail of P-366 Prehypertension and Mortality from Coronary Heart Disease and Stroke: 12 years of Follow-Up in Korean Men

CVD Prevention and Control, 2009