There have been several reports about the clinical association between type 2 diabetes mellitus (DM) and nonalcoholic fatty liver disease (NAFLD). However, most of the studies were about the unilateral effects of type 2 DM on NAFLD, and studies on the reverse relation are rare. Thus, this study was designed to investigate the effect of NAFLD on type 2 DM. We conducted a prospective cohort study on 25,232 Korean men without type 2 DM for 5 years. We serially checked the various metabolic factors including fasting glucose and hemoglobin A1c (HbA1c), and monitored the development of type 2 DM. The incidence rate of type 2 DM was compared according to the degree of NAFLD (normal, mild, and moderate to severe), and a Cox proportional hazards model was used to measure the hazard ratios (HRs) of NAFLD on type 2 DM. The incidence rate of type 2 DM increased according to the degree of NAFLD (normal: 7.0%, mild: 9.8%, moderate to severe: 17.8%, P < 0.001). Even after adjusting for other multiple covariates, the HRs (95% confidence interval [CI]) for type 2 DM development was higher in the mild group (1.09; 0.81-1.48) and moderate to severe group (1.73; 1.00-3.01) compared to the normal group, respectively ( P for trend <0.001). Conclusion : The development of type 2 DM is potentially more associated with more progressive NAFLD than a normal or milder state. In addition, NAFLD was an independent risk factor for the future development of type 2 DM. These results suggest the potential availability of NAFLD as an early predictor of type 2 DM.

OBJECTIVE Elevated serum ferritin has been known to be associated with the prevalence of metabolic syndrome (MetS). However, there was no research to examine whether serum ferritin levels have been actually associated with the prospective development of MetS. Accordingly, we carried out a prospective study to evaluate the longitudinal effects of baseline serum ferritin levels on the development of MetS. RESEARCH DESIGN AND METHODS A MetS-free cohort of 18,022 healthy Korean men, who had participated in a medical health checkup program in 2005, was followed until 2010. MetS was defined according to the joint interim statement of the International Diabetes Federation Task Force on Epidemiology and Prevention. Cox proportional hazards models were performed. RESULTS During 45,919.3 person-years of follow-up, 2,127 incident cases of MetS developed between 2006 and 2010. After adjusting for multiple covariates, the hazard ratios (95% CI) for incident MetS comparing the second quintile to the fifth quintile of serum ferritin levels versus the first quintile were 1.19 (0.98–1.45), 1.17 (0.96–1.43), 1.36 (1.12–1.65), and 1.66 (1.38–2.01), respectively (P for trend <0.001). These associations were apparent in the clinically relevant subgroup analyses. CONCLUSIONS Elevated serum ferritin levels were independently associated with future development of MetS during the 5-year follow-up period.

A growing body of literature has documented that job stress is associated with the development of work-related musculoskeletal disorders (WMSDs). However, the association of WMSDs with job stress has not yet been fully studied in Korean male firefighters. The purpose of this study was to determine the status of WMSDs in almost all Korean male firefighters and to clarify the effect of job stress on the occurrence of WMSDs. The study design was cross-sectional, and 21,466 firefighters were recruited. The study design included a structured questionnaire to assess general characteristics, the Korean Occupational Stress Scale (optional KOSS-26), Center for Epidemiologic Studies-Depression Scale (CES-D), and WMSDs. The chi-square test, and univariate and multivariate logistic regression analyses were used to look for a correlation between general characteristics and job stress, and the occurrence of WMSD. Back pain is the most common WMSD. Among the job stress subgroup, physical environment, job demands, organizational system, occupational climate, lack of reward and job insecurity were related to the occurrence of WMSDs. However, insufficient job control and interpersonal conflict were not related to the occurrence of WMSDs. Job stress was related to the occurrence of WMSDs in Korean male firefighters. To reduce the occurrence of WMSDs, a job stress management program may be required.

Recent studies have indicated the significant association between non-alcoholic fatty liver disease (NAFLD) and depression. However, there is ongoing debate on whether the risk for depression is actually related with the presence and severity of NAFLD. Thus, this study was conducted to investigate the association between depression and NAFLD evaluated by diverse modalities. A total of 112,797 participants from the Korean general population were enrolled. The study participants were categorized into three groups according to degree of NAFLD evaluated by ultrasonography, fatty liver index (FLI) and fibrosis-4 score (FIB-4). Depression was defined as a score of Center for Epidemiological Studies-Depression (CES-D) ≥ 16, and the odd ratios (ORs) and 95% confidence interval (CI) for depression (adjusted ORs [95% CI]) were assessed by multiple logistic regression analyses. In the unadjusted model, the presence and severity of NAFLD was not significantly associated with depressive symptoms. However, in the fully adjusted model, ORs for depression increased in proportion to the degree of ultrasonographically detected NAFLD (mild fatty liver: 1.14 [1.06-1.22]; and moderate to severe fatty liver: 1.32 [1.17-1.48]). An association was also observed between depression and FLI (30 ≤ FLI < 60: 1.06 [0.98-1.15]; FLI ≥ 60: 1.15 [1.02-1.29]). The presence and severity of NAFLD is significantly associated with depressive symptoms. In addition, this association was more distinct after adjusting for covariates including age, gender and insulin resistance. This finding indicates the necessity of further study evaluating the incidental relationship of depression with NAFLD.

Our study aimed to investigate the association between high-density lipoprotein cholesterol (HDL-C) and all-cause and cause-specific mortality in Korean adults. A total of 365,457 participants aged ≥40 years were selected from the Korean National Health Insurance Service-National Sample Cohort from 2009 to 2015. HDL-C level was categorized into <1.0, 1.0-1.19, 1.2-1.39, 1.4-1.59, 1.6-1.79 (reference), 1.8-1.99, 2.0-2.19 and ≥ 2.20 mmol/L. Cox proportional hazard models were used to examine the association between HDL-C level and mortality risk. In a median 3.5-year follow-up period, 9,350 participants (2.6%) died. Men with HDL-C level of 1.6-1.79 mmol/L and women with HDL-C level of 1.4-1.59 mmol/L had the lowest age-standardized mortality rates for all-cause death. However, for cardiovascular death, men with HDL-C level ≥2.20 mmol/L and women with HDL-C level of 1.8-1.99 mmol/L showed the lowest mortality rate. After adjusting for multiple covariates, the hazard ratios for all-cause and cancer deaths showed a U-shaped relationship with HDL-C level for both sexes. However, there were heterogenetic associations between HDL-C level and mortality risk of subtypes of cardiovascular disease by sex. For other causes of death except for cardiovascular and cancer death, elevated mortality risk was mainly due to external causes (ICD-10 code, S00-T98). In South Korea, very high HDL-C level was associated with increased risk of all-cause death. However, the increased all-cause mortality risk in people with very high HDL-C level was partly due to mortality risk from external causes.

Background: Components of the metabolic syndrome (MetS), such as elevated fasting glucose levels and abdominal obesity, have been suggested as potential risk factors for pancreatic cancer. However, data are still insufficient to assure the influence of MetS on incident pancreatic cancer. The objective of the current study was to investigate the association between MetS, metabolic components, and the risk of pancreatic cancer. Methods: In the Korea National Health Information Database, 223,138 individuals who were without pancreatic cancer in 2009 were enrolled and followed until 2013. They were categorized into 4 groups according to the number of baseline metabolic components (0, 1, 2, 3, and 4‐5). A multivariate Cox proportional hazard model was used to calculate the adjusted hazard ratios (HRs) and 95% CIs for incident pancreatic cancer according to the presence of MetS and the number of metabolic components. In addition, the risk of pancreatic cancer was evaluated in individuals who had a single metabolic component. Results: The presence of MetS was significantly associated with incident pancreatic cancer (adjusted HR, 1.47; 95% CI, 1.19‐1.81). The group with 4 or 5 baseline metabolic components had a higher risk of pancreatic cancer than the other groups (0 components: reference category; 1 component: adjusted HR, 0.94 [95% CI, 0.61‐1.45]; 2 components: adjusted HR, 1.03 [95% CI, 0.68‐1.56]; 3 components: adjusted HR, 1.35 [95% CI, 0.89‐2.04]; 4‐5 components: adjusted HR, 1.64 [95% CI, 1.06‐2.51]). Regarding associations between the individual metabolic components and pancreatic cancer, no metabolic component alone had a statistically significant association with pancreatic cancer. Conclusions: MetS is a potential risk factor for pancreatic cancer. The presence of ≥4 metabolic components leads to a higher risk of pancreatic cancer even within categories of the MetS.