Background: The Korean Endocrine Hormone Reference Standard Data Center (KEHRS DC) has created reference standards (RSs) for endocrine hormones since 2020. This study is the first of its kind, wherein the KEHRS DC established RSs for serum Cpeptide levels in a healthy Korean population. Methods: Healthy Korean adults were recruited from May 2021 to September 2023. After excluding participants according to our criteria, serum samples were collected; each participant could then choose between fasting glucose only or fasting glucose plus an oral glucose tolerance test (OGTT). If their sample showed high glucose (≥100 mg/dL) or hemoglobin A1c (HbA1c) (≥5.70%), their C-peptide levels were excluded from analyzing the RSs. Results: A total of 1,532 participants were recruited; however, only the data of 1,050 participants were analyzed after excluding those whose samples showed hyperglycemia or high HbA1c. Post-30-minute OGTT data from 342 subjects and post-120-minute OGTT data from 351 subjects were used. The means±2 standard deviations and expanded uncertainties of fasting, post-30-minute and 120-minute OGTT C-peptide levels were 1.26±0.82 and 0.34–3.18, 4.74±3.57 and 1.14–8.33, and 4.85±3.58 and 1.25–8.34 ng/mL, respectively. Serum C-peptide levels correlated with obesity, serum glucose levels, and HbA1c levels. Conclusion The RSs for serum C-peptide levels established in this study are expected to be useful in both clinical and related fields.

Purpose: An inverse relationship between cancer and neurodegenerative disease, which presents the possibility of a reduced risk of dementia in cancer patients, has been suggested previously. However, a nationwide longitudinal population-based study of specific types of cancer with due consideration of treatment effects has not been conducted. Materials and Methods: This nationwide population-based cohort study used data obtained in a 12-year period (January 2007- December 2018) in the Korean National Health Insurance claims database. All female breast cancer patients (age ≥ 50 years) diagnosed between 2009 and 2010 were included after excluding those with physician visits for any cancer during a 2-year period (2007-2008). Patients with senile cataract constituted the control group. The main study outcome was the risk of developing dementia. Results: From a total of 90,396 and 85,906 patients with breast cancer and cataract, respectively, patients without behavior codes were excluded. Data for 15,407 breast cancer patients and 7,020 controls were analyzed before matching. After matching for comorbidities and age, either group comprised 2,252 patients. The median follow-up time was 104.1±24.0 months after matching. After matching, breast cancer was a predictor of a lower risk of for dementia (hazard ratio, 0.091; 95% confidence interval, 0.075 to 0.111; p < 0.001). In breast cancer patients, receiving chemotherapy and endocrine therapy did not significantly affect the incidence of dementia. Conclusion Breast cancer was associated with a remarkably decreased risk of dementia. The findings strongly suggest an inverse relationship between cancer and neurodegeneration, regardless of the adverse effects of cancer treatment on cognitive function.

Background/Aims: Smoking is considered a risk factor for the development of nonalcoholic fatty liver disease (NAFLD). However, the association of a weight change after a change in smoking status and the risk of NAFLD remains undetermined. Methods: This study used the Korean National Health Insurance Service-National Sample Cohort. Based on the first (2009 to 2010) and second (2011 to 2012) health examination periods, 139,180 adults aged at least 40 years were divided into nonsmoking, smoking cessation, smoking relapse, and sustained smoking groups. NAFLD was operationally defined using the fatty liver index. The adjusted odds ratio (aOR) and 95% confidence interval (CI) were calculated using multivariable-adjusted logistic regression. Results: Compared to nonsmoking with no body mass index (BMI) change, the risk of NAFLD was significantly increased among subjects with BMI gain and nonsmoking (aOR, 4.07; 95% CI, 3.77 to 4.39), smoking cessation (aOR, 5.52; 95% CI, 4.12 to 7.40), smoking relapse (aOR, 7.51; 95% CI, 4.81 to 11.72), and sustained smoking (aOR, 6.65; 95% CI, 5.33 to 8.29), whereas the risk of NAFLD was reduced among participants with BMI loss in all smoking status groups. In addition, smoking cessation (aOR, 1.76; 95% CI, 1.35 to 2.29) and sustained smoking (aOR, 1.64; 95% CI, 1.39 to 1.94) were associated with higher risk of NAFLD among participants with no BMI change.The liver enzyme levels were higher among participants with smoking cessation and BMI gain. Conclusions Monitoring and management of weight change after a change in smoking status may be a promising approach to reducing NAFLD.

Background: Depression is a global mental health concern that negatively affects individuals’ health and increases medical costs. This study aimed to assess whether early depression management is cost-beneficial and effective from the perspective of quality indicators. Methods: Data of patients newly diagnosed with depressive disorder between 2012 and 2014 as well as follow-up data until 2020 were extracted from the National Health Insurance Service database. Hospitalization, emergency room visits, and annual medical expenses were set as dependent variables to estimate the effect of depression and information on medical expenditures. Six quality indicators developed by the Health Insurance Review and Assessment Service comprised independent variables. Results: In total, 465,766 patients were included in this study. Patients who met the quality indicators were more likely to be hospitalized with a psychiatric diagnosis. Furthermore, patients who met the quality indicator of revisiting within 3 weeks of their first visit had greater psychiatric and overall expenses during the early treatment phase; however, the overall expenses gradually decreased over time. Conclusion High-quality initial treatment for depression can be cost-effective in the long term; however, further studies are needed to discern its immediate clinical effects.

Background/Aims: Accumulating evidence suggests a link between non-alcoholic fatty liver disease (NAFLD) and brain health. However, population-based evidence on the association between NAFLD and dementia remains unclear. This study was conducted to determine the association between NAFLD and incident dementia. Methods: The study population included 608,994 adults aged ≥60 years who underwent health examinations between 2009 and 2010. Data were collected from the Korean National Health Insurance Service database. NAFLD was assessed using the fatty liver index (FLI). A Cox proportional hazards regression model was used to determine the association between NAFLD and dementia. Results: During the 6,495,352 person-years of follow-up, 48,538 participants (8.0%) developed incident dementia. The participants were classified into low (FLI <30), intermediate (FLI ≥30 and <60), and high (FLI ≥60) groups. In the overall study population, the FLI groups were associated with a risk of dementia (P for trend <0.001). After propensity score matching, a low FLI was associated with a reduced risk of dementia (adjusted hazard ration [aHR], 0.96; 95% confidence interval [CI], 0.93–0.98; P=0.002), whereas a high FLI (NAFLD) was associated with an increased risk of dementia (aHR, 1.05; 95% CI, 1.02–1.08; P=0.001). A higher risk of dementia in the high FLI group than in the intermediate FLI group was attributed to Alzheimer’s disease (aHR, 1.04; 95% CI, 1.01–1.07; P=0.004) rather than vascular dementia (aHR, 0.94; 95% CI, 0.75–1.18; P=0.602). Conclusions NAFLD was associated with an increased risk of dementia, which was attributed to an increased risk of Alzheimer’s disease.

Background/Aims: Metabolic dysfunction (MD)-associated fatty liver disease is a new positive diagnostic criterion based on hepatic steatosis and MD. However, a comprehensive evaluation on the association of MD and hepatic steatosis with incident cardiovascular disease (CVD) has yet to be performed. Methods: This retrospective cohort study included 333,389 participants from the Korean National Health Insurance Service database who received a health examination between 2009 and 2010. Hepatic steatosis was defined using the Korean National Health and Nutrition Examination Survey-derived nonalcoholic fatty liver disease scoring system. Cox proportional hazards regression was adopted to determine the adjusted hazard ratio (aHR) with 95% confidence interval (CI) for CVD according to the presence of hepatic steatosis and MD, as well as the composite term. Results: This study included 179,437 men and 153,952 women with a median age of 57 years.Hepatic steatosis with MD (aHR, 2.00; 95% CI, 1.89 to 2.13) and without MD (aHR, 1.30; 95% CI, 1.10 to 1.54) significantly increased the risk of CVD compared to no steatosis without MD (reference). However, steatosis revealed no significant difference in the risk of CVD compared to no steatosis among participants with one MD (aHR, 1.09; 95% CI, 0.91 to 1.30). In participants with steatosis, the presence of one and ≥2 MDs had aHR values of 1.25 (95% CI, 0.87 to 1.79) and 1.71 (95% CI, 1.22 to 2.41), respectively, compared to no MD. Conclusions Combined consideration of hepatic steatosis and MD was significantly associated with increased CVD risk and showed better predictive performance for CVD than hepatic steatosis or MD alone.

BACKGROUND/OBJECTIVES: The measurement of body composition, including muscle and fat mass, remains challenging in large epidemiological studies due to time constraint and cost when using accurate modalities. Therefore, this study aimed to develop and validate prediction equations according to sex to measure lean body mass (LBM), appendicular skeletal muscle mass (ASM), and body fat mass (BFM) using anthropometric measurement, serum creatinine level, and lifestyle factors as independent variables and dual-energy X-ray absorptiometry as the reference method. SUBJECTS/METHODS: A sample of the Korean general adult population (men:7,599; women:10,009) from the Korean National Health and Nutrition Examination Survey 2008–2011 was included in this study. The participants were divided into the derivation and validation groups via a random number generator (with a ratio of 70:30). The prediction equations were developed using a series of multivariable linear regressions and validated using the Bland– Altman plot and intraclass correlation coefficient (ICC). RESULTS: The initial and practical equations that included age, height, weight, and waist circumference had a different predictive ability for LBM (men: R2 = 0.85, standard error of estimate [SEE] = 2.7 kg; women: R2 = 0.78, SEE = 2.2 kg), ASM (men: R2= 0.81, SEE = 1.6 kg; women: R2 = 0.71, SEE = 1.2 kg), and BFM (men: R2 = 0.74, SEE = 2.7 kg; women: R2 = 0.83, SEE = 2.2 kg) according to sex. Compared with the first prediction equation, the addition of other factors, including serum creatinine level, physical activity, smoking status, and alcohol use, resulted in an R2 that is higher by 0.01 and SEE that is lower by 0.1. CONCLUSIONS All equations had low bias, moderate agreement based on the Bland–Altman plot, and high ICC, and this result showed that these equations can be further applied to other epidemiologic studies.

Purpose: Although smoking has a significant impact on mortality and morbidity of cancer patients, many patients continue to smoke post-diagnosis. The purpose of this study was to investigate prevalence and predictors of sustained smoking among male cancer survivors. Materials and Methods: The Korean National Health Insurance Service-National Health Screening Cohort database was used for this population-based, retrospective study. Study subjects were 15,141 men who were diagnosed with their first incident cancer between 2004 and 2011. Changes in smoking status before and after a cancer diagnosis were investigated. For patients who were current smokers pre-diagnosis, association between post-diagnosis sustained smoking and demographic, socioeconomic, and clinical variables were examined. Results: Of the 4,657 pre-diagnosis smokers, 2,255 (48%) had quit after cancer diagnosis, while 2,402 (51.6%) continued to smoke. In a multivariate logistic regression analysis, younger age at cancer diagnosis (adjusted odds ratio [aOR], 1.37; 95% confidence interval [CI], 1.21 to 1.55; p < 0.001), low socioeconomic status (aOR, 1.29; 95% CI, 1.15 to 1.45; p ≤ 0.001), pre-diagnosis heavy smoking (aOR, 1.24; 95% CI, 1.09 to 1.41; p=0.001), diagnosis of non-smoking– related cancer (aOR, 1.67; 95% CI, 1.42 to 1.96; p < 0.001), and high serum glucose level (aOR, 1.23; 95% CI, 1.03 to 1.46; p=0.019) were associated with sustained smoking after a cancer diagnosis. Conclusion Almost half of the male smokers continue to smoke after a cancer diagnosis. Targeted interventions for smoking cessation should be considered for patients with younger age, low socioeconomic status, heavy smoking history, non-smoking–related cancer, and high blood glucose levels.

PURPOSE: The purpose of this study was to investigate the effect of smoking habit change on the risk of cancer. MATERIALS AND METHODS: From the Korean National Health Insurance Service database, we determined the change in smoking habit between the first (2002 and 2003) and second (2004 and 2005) health examination periods. A total of 143,071 men were categorized into baseline heavy (≥ 20 cigarettes per day), moderate (10-19 cigarettes per day), light (< 10 cigarettes per day) smokers, quitters, and never smokers, after which the change in smoking status was determined during the second health examination. The participants were then followed up from 2006 to 2013 for all cancer, smoking related cancer, and lung cancer. RESULTS: Compared to heavy continual smokers, heavy smokers who quit had reduced risk of smoking related cancer (hazard ratio [HR], 0.74; 95% confidence interval [CI], 0.56 to 0.97) and tended to have reduced risk of all cancer (HR, 0.87; 95% CI, 0.75 to 1.00). Moderate smokers who reduced the amount of smoking to light levels had decreased risk of all cancer (HR, 0.82; 95% CI, 0.72 to 0.94), smoking related cancer (HR, 0.74; 95% CI, 0.59 to 0.93), and lung cancer (HR, 0.55; 95% CI, 0.38 to 0.79) compared to heavy continual smokers. CONCLUSION: Smoking reduction decreases the risk of all cancer, smoking related cancer, and lung cancer. While smoking cessation should be the treatment of choice for smokers, smoking reduction may serve as an alternative strategy for those who cannot quit.
Humans ; Lung Neoplasms ; Male ; National Health Programs ; Smoke* ; Smoking Cessation* ; Smoking* ; Tobacco Products

We investigated the adenoviral etiology and seasonal epidemic trends in intussusception and each adenoviral subgroup. Also we confirmed whether we can use the adenovirus data of Acute Infectious Agents Laboratory Surveillance Report (AIALSR) as an epidemic predictor of intussusception. Patients with intussusception (n = 126), < 5 years old, were enrolled and matched by age and sex with controls suffering acute gastroenteritis without intussusception (n = 106), all recruited at 8 centers. All fecal specimens were assayed for adenovirus, including subgroups A, B, C, E, and F, with reverse transcriptase-polymerase chain reaction (RT-PCR). Adenovirus was detected in 53 cases and 13 controls (P < 0.001). Nonenteric adenoviruses (NEAds) were detected in 51 cases and four controls (P < 0.001). We used Spearman's correlation analysis to analyze the incidence of intussusception and adenoviral epidemic trends, and compared them with fecal and respiratory adenoviral epidemic trends in the AIALSR. The trend of intussusception correlated with total NEAds (r = 0.635; P = 0.011), as did the fecal AIALSR adenovirus trends (r = 0.572; P = 0.026). Among the NEAd subgroups, subgroup C was dominant (P < 0.001), but subgroups B (P = 0.007) and E (P = 0.013) were also significant to intussusception. However, only subgroup C showed a significant epidemic correlation (r = 0.776; P = 0.001) with intussusception. Not respiratory but fecal AIALSR adenovirus trends correlated with the incidence of NEAds and intussusception. We suggest the possibility of using fecal AIALSR adenovirus data as an approximate epidemic predictor of intussusception.
Adenoviridae* ; Child ; Gastroenteritis ; Humans ; Incidence ; Intussusception* ; Korea* ; Seasons