BackgroundThe National Health Insurance Service (NHIS) recently signed an agreement to provide limited open access to the databases within the Korean Diabetes Association for the benefit of Korean subjects with diabetes. Here, we present the history, structure, contents, and way to use data procurement in the Korean National Health Insurance (NHI) system for the benefit of Korean researchers.MethodsThe NHIS in Korea is a single-payer program and is mandatory for all residents in Korea. The three main healthcare programs of the NHI, Medical Aid, and long-term care insurance (LTCI) provide 100% coverage for the Korean population. The NHIS in Korea has adopted a fee-for-service system to pay health providers. Researchers can obtain health information from the four databases of the insured that contain data on health insurance claims, health check-ups and LTCI.ResultsMetabolic disease as chronic disease is increasing with aging society. NHIS data is based on mandatory, serial population data, so, this might show the time course of disease and predict some disease progress, and also be used in primary and secondary prevention of disease after data mining.ConclusionThe NHIS database represents the entire Korean population and can be used as a population-based database. The integrated information technology of the NHIS database makes it a world-leading population-based epidemiology and disease research platform.

Obesity is associated with a reduced life expectancy, largely because obese individuals are at an increased risk of type 2 diabetes, cardiovascular disease, and several types of cancer. Much interest has recently focused on the concept of “all obesity is not created equally.” Obese individuals without the metabolic abnormalities that commonly accompany excess adiposity, a condition known as metabolically healthy obesity (MHO), account for a substantial proportion of the obese adult population. Numerous possible mechanisms underlying MHO have been suggested, including adipose tissue distribution and inflammation. However, the prognostic value of MHO is controversial and considerably challenging. The lack of a standard definition for metabolic health and obesity as well as the dynamic properties of MHO may have contributed to these inconsistent results. This review aimed to present several current issues regarding MHO including its definition, epidemiology, natural course, suggested mechanisms, and clinical implications in the context of patient prognosis.

Obesity has become an important risk factor for chronic kidney disease (CKD). The metabolically healthy obese (MHO) phenotype refers to obese individuals with a favorable metabolic profile. However, its prognostic value remains controversial and may depend on the health outcome being investigated. To assess this, we examined the risk of MHO phenotype with incident CKD in a Korean population of 41,194 people without CKD. Individuals were stratified by body mass index (cutoff value, 25.0 kg/m(2)) and metabolic health state (assessed using Adult Treatment Panel-III criteria). Incident CKD was defined as a glomerular filtration rate of <60 ml/min per 1.73 m(2) calculated using the Chronic Kidney Disease Epidemiology Collaboration equation. Over the median follow-up period of 38.7 months, 356 of the individuals developed incident CKD. Compared with the metabolically healthy nonobese (MHNO) group, the MHO group showed increased risk of incident CKD with a multivariate-adjusted hazard ratio of 1.38 (95% CI, 1.01-1.87). Nonobese but metabolically unhealthy individuals were at an increased risk of incident CKD (multivariate-adjusted hazard ratio, 1.37 (95% CI, 1.02-1.93)) than the MHNO group. Metabolically unhealthy obese individuals were at the highest risk of incident CKD. Thus, a healthy metabolic profile does not protect obese adults from incident CKD. Hence, it is important to consider metabolic health along with obesity when evaluating CKD risk.

BackgroundRepresentative data on the secular trends in cardiovascular disease (CVD) are limited in Asian populations with diabetes. We aimed to estimate the temporal trends in cardiovascular complications using Korean nationwide whole population-based claims data in subjects with and without diabetes.MethodsType 2 diabetes was defined as a current medication history of anti-diabetic drugs and the presence of International Classification of Diseases (ICD)-10 codes (E11–E14) as diagnosis. We compared the 8-year rates of six cardiovascular complications [i.e., ischemic heart disease, acute myocardial infarction (AMI), ischemic stroke, hemorrhagic stroke, percutaneous coronary intervention (PCI), and coronary artery bypass graft (CABG)] in Korean adults aged 30 years and older using data from four consecutive nationwide databases (2006–2007, 2008–2009, 2010–2011, and 2012–2013) of Korean national health insurance service.ResultsA total of 1,645,348, 1,971,559, 2,291,247, and 2,562,612 subjects with type 2 diabetes were found in the year of 2006–2007, 2008–2009, 2010–2011, and 2012–2013, respectively. Age and gender standardized rates of the six predefined cardiovascular complications decreased in Korean adults with type 2 diabetes during the study period. The greatest relative reductions were observed for hospitalization due to AMI (−37.28%), followed by hospitalizations due to ischemic stroke (−36.98%). In the overall population without type 2 diabetes, the greatest relative reductions were observed for hospitalization for hemorrhagic stroke (−29.47%), followed by hospitalization due to ischemic stroke (−28.92%). Relative decreases in all six predefined cardiovascular complications were generally more profound in adults with diabetes than in those without diabetes, which led to significant decrease in the relative risks of all six cardiovascular complications in subjects with diabetes over the past 8 years. However, people with diabetes still had a two- to sixfold higher risk of hospitalization for major CVD events and interventions than people without diabetes.ConclusionsOur findings suggest a significant reduction in the rate of people affected by CVD within the diabetic population. However, as the number of people with diabetes rises, the absolute burden of CVD will still be high in Korea.Electronic supplementary materialThe online version of this article (doi:10.1186/s12933-016-0482-6) contains supplementary material, which is available to authorized users.

MHO subjects show a substantially higher risk of incident type 2 diabetes than MHNO subjects. The level of systemic inflammation partially explains this increased risk.

The rapidly increasing prevalence of obesity confers a huge health burden globally. The hypothalamus plays a central role in the regulation of energy homeostasis by integrating multiple metabolic signals from peripheral organs and modulating feeding behavior and energy metabolism. Leptin, a key appetite-regulating hormone derived from the white adipose tissue, primarily acts on hypothalamic neurons to activate catabolic pathway and inhibit anabolic pathway, which can result in anorexia and weight reduction. Despite striking obesity resulting from leptin deficiency, treatment with this hormone in human obesity has been unsuccessful due to leptin resistance. In this review, we describe recent researches extending our understanding of obesity-associated hypothalamic leptin resistance.

Korea's National Healthcare Program, the National Health Insurance Service (NHIS), a government-affiliated agency under the Korean Ministry of Health and Welfare, covers the entire Korean population. The NHIS supervises all medical services in Korea and establishes a systematic National Health Information database (DB). A health information DB system including all of the claims, medications, death information, and health check-ups, both in the general population and in patients with various diseases, is not common worldwide. On June 9, 2014, the NHIS signed a memorandum of understanding with the Korean Diabetes Association (KDA) to provide limited open access to its DB. By October 31, 2017, seven papers had been published through this collaborative research project. These studies were conducted to investigate the past and current status of type 2 diabetes mellitus and its complications and management in Korea. This review is a brief summary of the collaborative projects between the KDA and the NHIS over the last 3 years. According to the analysis, the national health check-up DB or claim DB were used, and the age category or study period were differentially applied.

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