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.

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.

Background: Lifestyle-related factors have been studied as a fundamental aspect in the onset and progression of type 2 diabetes mellitus. However, behavioral factors are easily overlooked in clinical practice. This study investigated whether lifestyle changes were associated with diabetes remission in newly diagnosed type 2 diabetes patients. Methods: We enrolled patients with new-onset type 2 diabetes from 2009 to 2012 using a health examination cohort from the Korean National Health Insurance Service (KNHIS).Remission was defined as a fasting glucose level less than 126 mg/dL at least once during a health examination after stopping medication. A self-administered questionnaire was used to investigate patients’ lifestyles. We investigated smoking, alcohol consumption, and regular exercise before and after starting diabetes medication and the odds ratios (ORs) of logistic regression on remission to evaluate the associations. Results: A total of 138,211 patients diagnosed with type 2 diabetes from 2009 to 2012 were analyzed, and 8,192 (6.3%) reported remission during the follow-up period to 2017. Baseline fasting blood glucose level measured before starting diabetes medication was significantly higher in the non-remission group (180 mg/dL vs. 159 mg/dL, P < 0.001). In addition, the use rate of combined oral hypoglycemic agent treatment was higher in the non-remission group (15% vs. 8%, P < 0.001). Consistent smoking and drinking showed negative associations with remission (OR, 0.72; 95% confidence interval [CI], 0.67–0.77 and OR, 0.90; 95% CI, 0.84– 0.95, respectively), and initiation of regular exercise presented a positive association with remission (OR, 1.54; 95% CI, 0.46–1.63). Abstinence from alcohol increased the likelihood of remission in the male population (OR, 1.20; 95% CI, 1.10–1.32). The association with smoking history or smoking cessation was not clear, but new smoking behavior interfered with remission in women (OR, 0.48; 95% CI, 0.28–0.81). Conclusion We confirmed associations between a healthy lifestyle and diabetic remission in new-onset type 2 diabetes patients. The results of this study suggest that improving lifestyle after diabetes diagnosis may contribute to disease remission.

Objective: The association of lipid parameters with cardiovascular disease (CVD) and the impact of kidney function on this association have not been thoroughly evaluated in patients with type 2 diabetes mellitus (T2DM). Methods: Using the Korean National Health Insurance Service Cohort database, we identified 2,343,882 subjects with T2DM in 2015–2016. Baseline lipid levels and kidney function were evaluated and followed up until December 2020. Subjects were classified into three groups according to their estimated glomerular filtration rate (eGFR): ≥60, 30–59, or <30 mL/min/ 1.73 m2 . We analyzed the diabetes group with eGFR ≥60 and low-density lipoprotein cholesterol (LDL-C) <70 mg/dL as a reference group. Results: The risk of CVD began to increase at LDL-C ≥100 mg/dL in the eGFR ≥60 mL/min/m2group. The risk of CVD in the eGFR 30–59 mL/min/m2 group was increased by 43%, even in the LDL-C <70 mg/dL, and the risk increased progressively with LDL-C category. Among subjects with eGFR 30–59 mL/min/m2 , LDL-C 70–99, 100–129, 130–159, and ≥160 mg/ dL were significantly associated with the risk of CVD, with hazard ratio (95% confidence interval) of 1.48 (1.43–1.53), 1.54 (1.49–1.60), 1.55 (1.48–1.63), and 1.88 (1.77–2.00), respectively. In the eGFR <30 mL/min/m2 group, a 3.3-fold increased risk of CVD was seen, even at LDL-C <70 mg/dL. Conclusion The cutoff levels of LDL-C that increase CVD risk in patients with T2DM depend on kidney function, which influences the relationship between LDL-C and CVD risk in patients with T2DM.

Background: Lifestyle-related factors have been studied as a fundamental aspect in the onset and progression of type 2 diabetes mellitus. However, behavioral factors are easily overlooked in clinical practice. This study investigated whether lifestyle changes were associated with diabetes remission in newly diagnosed type 2 diabetes patients. Methods: We enrolled patients with new-onset type 2 diabetes from 2009 to 2012 using a health examination cohort from the Korean National Health Insurance Service (KNHIS).Remission was defined as a fasting glucose level less than 126 mg/dL at least once during a health examination after stopping medication. A self-administered questionnaire was used to investigate patients’ lifestyles. We investigated smoking, alcohol consumption, and regular exercise before and after starting diabetes medication and the odds ratios (ORs) of logistic regression on remission to evaluate the associations. Results: A total of 138,211 patients diagnosed with type 2 diabetes from 2009 to 2012 were analyzed, and 8,192 (6.3%) reported remission during the follow-up period to 2017. Baseline fasting blood glucose level measured before starting diabetes medication was significantly higher in the non-remission group (180 mg/dL vs. 159 mg/dL, P < 0.001). In addition, the use rate of combined oral hypoglycemic agent treatment was higher in the non-remission group (15% vs. 8%, P < 0.001). Consistent smoking and drinking showed negative associations with remission (OR, 0.72; 95% confidence interval [CI], 0.67–0.77 and OR, 0.90; 95% CI, 0.84– 0.95, respectively), and initiation of regular exercise presented a positive association with remission (OR, 1.54; 95% CI, 0.46–1.63). Abstinence from alcohol increased the likelihood of remission in the male population (OR, 1.20; 95% CI, 1.10–1.32). The association with smoking history or smoking cessation was not clear, but new smoking behavior interfered with remission in women (OR, 0.48; 95% CI, 0.28–0.81). Conclusion We confirmed associations between a healthy lifestyle and diabetic remission in new-onset type 2 diabetes patients. The results of this study suggest that improving lifestyle after diabetes diagnosis may contribute to disease remission.

Objective: The association of lipid parameters with cardiovascular disease (CVD) and the impact of kidney function on this association have not been thoroughly evaluated in patients with type 2 diabetes mellitus (T2DM). Methods: Using the Korean National Health Insurance Service Cohort database, we identified 2,343,882 subjects with T2DM in 2015–2016. Baseline lipid levels and kidney function were evaluated and followed up until December 2020. Subjects were classified into three groups according to their estimated glomerular filtration rate (eGFR): ≥60, 30–59, or <30 mL/min/ 1.73 m2 . We analyzed the diabetes group with eGFR ≥60 and low-density lipoprotein cholesterol (LDL-C) <70 mg/dL as a reference group. Results: The risk of CVD began to increase at LDL-C ≥100 mg/dL in the eGFR ≥60 mL/min/m2group. The risk of CVD in the eGFR 30–59 mL/min/m2 group was increased by 43%, even in the LDL-C <70 mg/dL, and the risk increased progressively with LDL-C category. Among subjects with eGFR 30–59 mL/min/m2 , LDL-C 70–99, 100–129, 130–159, and ≥160 mg/ dL were significantly associated with the risk of CVD, with hazard ratio (95% confidence interval) of 1.48 (1.43–1.53), 1.54 (1.49–1.60), 1.55 (1.48–1.63), and 1.88 (1.77–2.00), respectively. In the eGFR <30 mL/min/m2 group, a 3.3-fold increased risk of CVD was seen, even at LDL-C <70 mg/dL. Conclusion The cutoff levels of LDL-C that increase CVD risk in patients with T2DM depend on kidney function, which influences the relationship between LDL-C and CVD risk in patients with T2DM.

Background: The impact of weight or weight changes on kidney function remains a matter of debate. This study aimed to investigate the association between weight fluctuation and the incidence of end-stage renal disease (ESRD) using data from the Korean National Health Insurance Corporation health checkups (2009–2015). Methods: The study included 2,310,667 participants (1,546,749 men and 763,918 women), aged ≥40 years. Weight fluctuation was assessed using the average real variability (ARV) of weight and categorized into quartiles (Q1–Q4). Hazard ratios (HRs) and 95% confidence intervals for ESRD incidence were calculated using multivariable Cox proportional hazards models. Results: After adjustment for comorbidities, increased body mass index was associated with a decreased HR for ESRD. The highest quartile of weight variability (ARV Q4) demonstrated a higher probability and HR for ESRD compared to the lower variability quartiles (Q1–Q3). Among men, individuals with sustained weight, and those with weight gain, the ARV Q4 group showed significantly increased HRs for ESRD (HR of 1.372, 1.222, and 1.49, respectively). Furthermore, irrespective of changes in creatinine levels, all ARV Q4 groups exhibited increased HRs for ESRD (HR of 1.342, 1.472, and 1.299, respectively). Conclusions High weight fluctuation (ARV Q4) was associated with an increased incidence of ESRD in the general Korean population, with notable significance in men and in groups with sustained or increased weight. Clinically, individuals in the ARV Q4 category should be considered at risk for ESRD, and early interventions should be pursued for this population.

The number of large-scale epidemiological studies using administrative databases has rapidly increased in recent years. However, in observational studies, the outcomes of interest are heavily influenced by concurrent or pre-existing comorbidities, which act as confounders, and appropriate adjustment of comorbidities is essential to minimize bias. Although several comorbidity indices are available for this purpose, Charlson comorbidity index (CCI) is the most widely used one. The original version of the CCI was developed for use in longitudinal studies, to classify comorbidities that might alter the risk of mortality. It included 19 comorbidities, with each comorbidity having an assigned weight from 1 to 6; the total CCI score is a simple sum of the weights. Although the original CCI was based on a review of medical records, many modified versions have been proposed in subsequent studies using claims data. The CCI and its modified versions are used in virtually all clinical settings, including oncology, cardiology, respiratory care, emergency care, surgery, intensive care, and geriatrics. Appropriate use of a comorbidity index, such as the CCI, is necessary to minimize bias in observational studies in the era of increasing use of administrative data for healthcare research.

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.