Purpose: Previous studies from mostly Western populations have suggested possible associations between obesity and melanoma risk. This study aimed to investigate associations between obesity status and melanoma using a nationwide cohort of Koreans. Materials and Methods: A total of 4,441,403 adults who received a national health examination in 2012 were included from the Korean National Health Insurance Service database, and followed until December 31, 2022. Obesity status was defined based on the body mass index at the baseline health examination. Cox proportional hazards analyses were performed to evaluate associations between obesity status and incident melanoma, with adjustment for confounders. Stratified analyses were performed by sex and menopausal status (in women). Results: Overall, melanoma risk increased according to obesity status (p for trend=0.024); adjusted hazard ratios (95% confidence intervals) for melanoma risk were 0.766 (0.438–1.340) in underweight; 1.292 (1.072–1.557) in overweight; 1.202 (1.002–1.442) in obesity; and 1.191 (0.798–1.778) in severe obesity compared to normal weight (reference). In stratified analyses, similar trends to those of the overall study population were observed among men and premenopausal women (p for trend=0.052 in men and 0.036 in premenopausal women). Among premenopausal women, the risk of melanoma increased linearly with obesity status. Meanwhile, among postmenopausal women, melanoma risk showed no significant difference or trend according to obesity status. Conclusion Overweight and obesity were associated with increased risk of melanoma in a population-based cohort of Koreans. Obese individuals, especially men and premenopausal women, may require more thorough prevention and screening strategies for melanoma.

Background/Aims: We examined the association between diabetes duration and hyperuricemia in Korean subjects based on data from the Korea National Health and Nutrition Examination Survey (KNHANES). Methods: This cross-sectional study included 4,575 subjects aged 30 years and older with type 2 diabetes mellitus based on data from the KNHANES from 2016 to 2021. Hyperuricemia was defined as a serum uric acid level ≥ 7.0 mg/dL. Univariable and multivariable logistic regression models were used calculate adjusted odds ratios (ORs) and their 95% confidence intervals (CIs). Results: The mean age of subjects was 61.0 years, 56.5% were male, and the mean body mass index (BMI) was 25.6 kg/m2. Compared to those with diabetes duration 5 to < 10 years, those with shorter or longer diabetes duration had higher serum uric acid levels and higher prevalence of hyperuricemia. In multivariable logistic regression models, a U-shaped association between diabetes duration and hyperuricemia was observed after adjusting for age, sex, income, smoking status, alcohol consumption, regular exercise, and presence of hypertension, dyslipidemia, or chronic kidney disease. Compared to those with new-onset diabetes mellitus, the adjusted OR (95% CI) for hyperuricemia was 0.55 (0.38–0.82) in those with diabetes duration 5 to < 10 years. The results were consistent in subgroup analysis according to age, sex, BMI, and chronic kidney disease. Conclusions The U-shaped association between diabetes duration and hyperuricemia was observed in a representative sample of Korean adults.

Background: Psoriasis is acknowledged for its association with diabetes and obesity. However, the comprehension of the correlation between obesity and psoriasis risk in individuals with diabetes remains limited. Objective: We aimed to examine the association of body mass index and waist circumference (WC) with the risk of developing psoriasis in individuals with type 2 diabetes mellitus (T2DM). Methods: This retrospective cohort study utilized nationwide data for exploratory analysis.A total of 2,480,489 participants, all diagnosed with T2DM, were included. Results: Over a 6.77±1.69-year follow-up, 71,514 patients (2.88%) were diagnosed with psoriasis. Adjusting for multiple variables, the study revealed a J-shaped pattern association between BMI levels and the hazard ratio (HR) for psoriasis in patients with T2DM. A linear pattern relationship was observed regarding WC, with the highest WC group showing the most elevated HR (HR, 1.123; 95% confidence interval, 1.091–1.156). Conclusion Understanding the relationship between psoriasis risk and obesity in diabetic individuals holds the potential to enhance the management of patients with T2DM.

Objective: This study aimed to assess the association between exposure to gadolinium-based contrast agents (GBCAs) and the risk of parkinsonism according to the GBCA type. Materials and Methods: Individuals aged ≥40 years who underwent first-ever magnetic resonance imaging (MRI) examinations between 2011 and 2014 were identified from the Korean nationwide population-based health insurance claims database and followed up until 2022. Individuals were divided into those who underwent at least one GBCA-enhanced MRI, and those who underwent only non-enhanced MRI. GBCA-exposed individuals were further categorized into those exposed only to linear or macrocyclic GBCAs, after excluding those exposed to both types. The primary event of interest was allcause parkinsonism. Secondary events included all-cause parkinsonism requiring medication, Parkinson’s disease (PD), atypical parkinsonism, and secondary parkinsonism. Hazard ratios (HRs) were estimated using multivariable Cox proportional hazard regression models for exposure to linear and macrocyclic GBCAs, with the non-enhanced MRI group serving as a reference. The models were adjusted for age, sex, smoking status, alcohol consumption, regular exercise, body mass index, estimated glomerular filtration rate, and comorbidities. Subgroup analyses were performed according to age, sex, renal function, and history of cancer. Results: A total of 222,977 individuals were included in this study. Among them, 92,230, 48,335, and 82,412 individuals underwent non-enhanced, linear GBCA-enhanced, and macrocyclic GBCA-enhanced MRI, respectively. Exposure to linear GBCAs slightly increased the risk of all-cause parkinsonism (adjusted HR, 1.13 [97.5% confidence interval, 1.08–1.19]), while exposure to macrocyclic GBCAs did not increase the risk (adjusted HR, 1.00 [97.5% confidence interval, 0.95–1.05]).The results were similar for all-cause parkinsonism requiring medication, PD, and secondary parkinsonism, whereas no significant association was observed for atypical parkinsonism. Conclusion Exposure to linear GBCAs may slightly increase the risk of parkinsonism in adults, whereas exposure to macrocyclic GBCAs may not. Caution should be exercised when using linear GBCAs until further evidence emerges.

Background/Aims: This study aimed to evaluate the impact of steatotic liver disease severity on the cumulative incidence of lung cancer utilizing data from the Korea National Health Insurance Service (NHIS). Methods: This study examined the risk of lung cancer in the general population in conjunction with the incidence of steatotic liver disease. The study population consisted of 3,261,438 individuals aged 20 years or older who underwent a general health examination in 2009. Results: Individuals with fatty liver index (FLI) of 30–59 exhibited a 1.08-fold increased risk of lung cancer (95% CI: 1.04–1.11), while FLI ≥ 60 was associated with a 1.22-fold elevated risk of lung cancer (95% CI: 1.17–1.28) compared to those with FLI < 30. The risk varied with smoking status; in current smokers, the adjusted HR for the FLI 30–59 group was 1.05 (95% CI: 1.00–1.10), while that in the FLI ≥ 60 group was 1.11 (95% CI: 1.04–1.18). In never- or past-smokers, the adjusted HR for the FLI 30–59 group was 1.10, and that for the FLI ≥ 60 group was 1.31. Subgroup analysis revealed an incidence rate of 1.06 per 1,000 person-years in the consistently high FLI group compared to 1.15 in those with improved FLI. Improving FLI over time was associated with a 0.93-fold decrease in lung cancer risk. Conclusions Our study demonstrated a correlational relationship between lung cancer incidence and the severity of steatotic liver disease as measured by FLI.

Purpose: Smoking may have a protective role in developing ulcerative colitis (UC) but have the opposite effect on Crohn’s disease (CD). This study aimed to determine the risk of developing inflammatory bowel disease (IBD) according to smoking status and onset age of smoking. Materials and Methods: We collected data on the smoking experiences of participants aged 20–39 years who underwent biannual examinations provided by the Korean National Health Screening Program from 2009 to 2012. IBD diagnosis was identified using the National Health Insurance Service. The risk of IBD according to smoking status and onset age of smoking was analyzed after adjusting for major clinical variables. Results: During a median 10.59-year follow-up, the risk of UC in ex-smokers was significantly higher than that in non-smokers, and the earlier ex-smokers started smoking, the higher risk of UC [ex-smokers whose onset age of smoking was <20 years, adjusted hazard ratio (aHR) 1.928, 95% confidence interval (CI)=1.649–2.255; 20–24 years, aHR 1.728, 95% CI=1.541–1.939; 25–29 years, aHR 1.676, 95% CI=1.489–1.887; ≥30 years, aHR 1.226, 95% CI=1.010–1.486]. The risk of UC was significantly lower in current smokers whose onset age of smoking was 25–29 years than in non-smokers (aHR 0.825, 95% CI=0.709–0.959). The risk of CD did not differ according to smoking status and onset age of smoking. Conclusion Ex-smokers who started smoking at a young age have a high risk of UC, even after adjusting for the smoking amount.

The Korean National Health Information Database (NHID), which contains nationwide real-world claims data including sociodemographic data, health care utilization data, health screening data, and healthcare provider information, is a powerful resource to test various hypotheses. It is also longitudinal in nature due to the recommended health checkup every 2 years and is appropriate for long-term follow-up study as well as evaluating the relationships between health outcomes and changes in parameters such as lifestyle factors, anthropometric measurements, and laboratory results. However, because these data are not collected for research purposes, precise operational definitions of diseases are required to facilitate big data analysis using the Korean NHID. In this review, we describe the characteristics of the Korean NHID, operational definitions of diseases used for research related to diabetes, and introduce representative research for diabetes-related diseases using the Korean NHID.

Background: The relationship between circulating lipid levels and the risk for heart failure (HF) is controversial. We aimed to examine this association, and whether it is modified by the duration of diabetes or treatment regimens in people with type 2 diabetes mellitus. Methods: Individuals (n=2,439,978) who underwent health examinations in 2015 to 2016 were identified from the Korean National Health Information Database. Subjects were categorized according to the duration of diabetes (new-onset, <5, 5–10, or ≥10 years) and number of antidiabetic medications. Incident HF was defined according to the International Classification of Diseases, 10th Revision (ICD-10) code I50 as the primary diagnosis during hospitalization. The risk for HF was estimated using multivariate Cox proportional hazard analysis. Results: During a median follow-up of 4.0 years, 151,624 cases of HF occurred. An inverse association between low-density lipoprotein cholesterol (LDL-C) levels and incident HF was observed in the new-onset diabetes group, with an approximately 25% lower risk in those with LDL-C levels of 100–129, 130–159, and ≥160 mg/dL, compared to those with levels <70 mg/dL. However, J-shaped associations were noted in the long-standing diabetes group, with a 16% higher risk in those with LDL-C level ≥160 mg/dL, compared to those with levels <70 mg/dL. Similar patterns were observed in the relationship between total cholesterol or non-high-density lipoprotein cholesterol and the risk for HF, and when subjects were grouped according to the number of antidiabetic medications instead of diabetes duration. Conclusion Different associations between lipid levels and the risk for HF were noted according to disease progression status among individuals with diabetes.

Background: Limited data are available on the adverse effects of new-onset diabetes after transplantation (NODAT) in solid organ transplantation (TPL) other than kidney. This study aimed to identify the risk of complications associated with NODAT in recipients of kidney, liver, or heart TPL. Methods: Using the Korean National Health Insurance Service database, recipients of kidney, liver, or heart TPL between 2009 and 2015 were identified. The incidence of coronary artery disease (CAD), cerebrovascular accident (CVA), and malignancy was compared across groups with NODAT, pretransplant diabetes mellitus (DM), and without DM using Cox regression analysis. Results: A total of 9,632 kidney, liver, or heart TPL recipients were included. During the median follow-up of 5.9 years, NODAT independently increased the incidence of CAD (hazard ratio [HR], 2.46; 95% confidence interval [CI], 1.39 to 4.30) and overall mortality (HR, 1.48; 95% CI, 1.14 to 1.95) compared to the reference group even after adjustment for confounders; this was more prominent in kidney TPL than in liver TPL. The risk of CVA was significantly increased by pretransplant DM but not by NODAT in both kidney and liver TPL (HR, 2.47; 95% CI, 1.68 to 3.65; and HR, 3.18; 95% CI, 1.07 to 9.48, respectively). NODAT increased the risk of malignancy in the crude model, which lost its statistical significance after confounder adjustment. Conclusion NODAT independently increases the risk of CAD and mortality after TPL, which is more evident in kidney recipients. There was no additional increased risk of CVA or malignancy with NODAT in solid organ TPL.

Background: Diabetes in older adults is becoming a significant public burden to South Korea. However, a comprehensive understanding of epidemiologic trends and the detailed clinical characteristics of older adults with diabetes is lacking. Therefore, we evaluated epidemiologic trends and the metabolic and lifestyle characteristics of diabetes in Korean older adults. Methods: We analyzed data from the Korea National Health and Nutrition Examination Survey to assess diabetes prevalence according to diabetes duration and lifestyle behaviors. In addition, we drew upon the National Health Information Database of the National Health Insurance System to assess physical activity levels, antidiabetic medication use, polypharmacy, medication adherence, and major comorbidities. Results: The absolute number of newly diagnosed cases of diabetes among older adults doubled over the past decade. Management rates of metabolic indicators were higher in older adults with diabetes compared to those without diabetes. The proportion of older adults with diabetes meeting the minimum recommended physical activity increased over the years. Compared to 10 years before, the use of dipeptidyl peptidase-4 inhibitor or sodium-glucose cotransporter-2 inhibitor had increased, as had comorbidities such as dyslipidemia, dementia, cancer, heart failure, atrial fibrillation, and chronic kidney disease. Initial medication adherence was significantly lower in those with end-stage kidney disease or dementia, insulin use, high-risk alcohol use, and living alone. Continuing insulin use 1 year after diagnosis of diabetes was significantly higher in those who initiated insulin therapy at diagnosis, had retinopathy, were on triple antidiabetic medications, and had a history of cancer. Conclusion Comprehensive management of metabolic indicators and physical activity is essential for older adults with diabetes. Improvements in prescribing guidelines, personalized management of age-related comorbidities, and individualized approaches that consider the heterogeneous nature of older adults with diabetes are desirable. Further research, such as high-quality cohort and intervention studies specific to older adults, is needed to establish evidence-based management for older adults with diabetes.