OBJECTIVES: We aimed to assess the impact of obesity on mortality in middle-aged Koreans using data from a Health Examinees study. METHODS: We used data from the participants who had complete information on body size and gave informed consent for the linkage of their data with the national death certificate data. Cox proportional hazard model was used to estimate the hazard ratios and 95% confidence intervals (CIs) of body mass index (BMI) and waist-to-hip ratio (WHR) for all-cause, cardiovascular, and cancer mortality. RESULTS: A total of 115,961 participants were included in the study. The results showed a U-shaped association between BMI and mortality, indicating that both males and females with BMIs of less than 21.0 kg/m2 and greater than or equal to 30.0 kg/m2 are at increased risk. The results showed that males with a BMI of less than 18.5 kg/m² had a significantly higher risk of all-cause mortality (adjusted hazard ratio [aHR], 2.24; 95% CI, 1.73 to 2.91) and cardiovascular mortality (aHR, 2.27; 95% CI, 1.23 to 4.20). Similarly, males with a WHR of less than 0.80 (aHR, 1.38; 95% CI, 1.08 to 1.77), 0.90 to less than 0.95 (aHR, 1.15; 95% CI, 1.02 to 1.29), and greater than or equal to 0.95 (aHR, 1.28; 95% CI, 1.11 to 1.47) showed an increased risk of all-cause mortality. In females, a BMI of less than 18.0 kg/m2 was linked to a higher risk of cardiovascular mortality (aHR, 2.67; 95% CI, 1.13 to 6.33). CONCLUSIONS Being underweight was associated with an increased risk of mortality in both sexes, and the lowest risk of death was found in males who were slightly overweight with a BMI of 23.0-25.0 kg/m2.

OBJECTIVES: We aimed to assess the impact of obesity on mortality in middle-aged Koreans using data from a Health Examinees study. METHODS: We used data from the participants who had complete information on body size and gave informed consent for the linkage of their data with the national death certificate data. Cox proportional hazard model was used to estimate the hazard ratios and 95% confidence intervals (CIs) of body mass index (BMI) and waist-to-hip ratio (WHR) for all-cause, cardiovascular, and cancer mortality. RESULTS: A total of 115,961 participants were included in the study. The results showed a U-shaped association between BMI and mortality, indicating that both males and females with BMIs of less than 21.0 kg/m2 and greater than or equal to 30.0 kg/m2 are at increased risk. The results showed that males with a BMI of less than 18.5 kg/m² had a significantly higher risk of all-cause mortality (adjusted hazard ratio [aHR], 2.24; 95% CI, 1.73 to 2.91) and cardiovascular mortality (aHR, 2.27; 95% CI, 1.23 to 4.20). Similarly, males with a WHR of less than 0.80 (aHR, 1.38; 95% CI, 1.08 to 1.77), 0.90 to less than 0.95 (aHR, 1.15; 95% CI, 1.02 to 1.29), and greater than or equal to 0.95 (aHR, 1.28; 95% CI, 1.11 to 1.47) showed an increased risk of all-cause mortality. In females, a BMI of less than 18.0 kg/m2 was linked to a higher risk of cardiovascular mortality (aHR, 2.67; 95% CI, 1.13 to 6.33). CONCLUSIONS Being underweight was associated with an increased risk of mortality in both sexes, and the lowest risk of death was found in males who were slightly overweight with a BMI of 23.0-25.0 kg/m2.

OBJECTIVES: We aimed to assess the impact of obesity on mortality in middle-aged Koreans using data from a Health Examinees study. METHODS: We used data from the participants who had complete information on body size and gave informed consent for the linkage of their data with the national death certificate data. Cox proportional hazard model was used to estimate the hazard ratios and 95% confidence intervals (CIs) of body mass index (BMI) and waist-to-hip ratio (WHR) for all-cause, cardiovascular, and cancer mortality. RESULTS: A total of 115,961 participants were included in the study. The results showed a U-shaped association between BMI and mortality, indicating that both males and females with BMIs of less than 21.0 kg/m2 and greater than or equal to 30.0 kg/m2 are at increased risk. The results showed that males with a BMI of less than 18.5 kg/m² had a significantly higher risk of all-cause mortality (adjusted hazard ratio [aHR], 2.24; 95% CI, 1.73 to 2.91) and cardiovascular mortality (aHR, 2.27; 95% CI, 1.23 to 4.20). Similarly, males with a WHR of less than 0.80 (aHR, 1.38; 95% CI, 1.08 to 1.77), 0.90 to less than 0.95 (aHR, 1.15; 95% CI, 1.02 to 1.29), and greater than or equal to 0.95 (aHR, 1.28; 95% CI, 1.11 to 1.47) showed an increased risk of all-cause mortality. In females, a BMI of less than 18.0 kg/m2 was linked to a higher risk of cardiovascular mortality (aHR, 2.67; 95% CI, 1.13 to 6.33). CONCLUSIONS Being underweight was associated with an increased risk of mortality in both sexes, and the lowest risk of death was found in males who were slightly overweight with a BMI of 23.0-25.0 kg/m2.

OBJECTIVES: We aimed to assess the impact of obesity on mortality in middle-aged Koreans using data from a Health Examinees study. METHODS: We used data from the participants who had complete information on body size and gave informed consent for the linkage of their data with the national death certificate data. Cox proportional hazard model was used to estimate the hazard ratios and 95% confidence intervals (CIs) of body mass index (BMI) and waist-to-hip ratio (WHR) for all-cause, cardiovascular, and cancer mortality. RESULTS: A total of 115,961 participants were included in the study. The results showed a U-shaped association between BMI and mortality, indicating that both males and females with BMIs of less than 21.0 kg/m2 and greater than or equal to 30.0 kg/m2 are at increased risk. The results showed that males with a BMI of less than 18.5 kg/m² had a significantly higher risk of all-cause mortality (adjusted hazard ratio [aHR], 2.24; 95% CI, 1.73 to 2.91) and cardiovascular mortality (aHR, 2.27; 95% CI, 1.23 to 4.20). Similarly, males with a WHR of less than 0.80 (aHR, 1.38; 95% CI, 1.08 to 1.77), 0.90 to less than 0.95 (aHR, 1.15; 95% CI, 1.02 to 1.29), and greater than or equal to 0.95 (aHR, 1.28; 95% CI, 1.11 to 1.47) showed an increased risk of all-cause mortality. In females, a BMI of less than 18.0 kg/m2 was linked to a higher risk of cardiovascular mortality (aHR, 2.67; 95% CI, 1.13 to 6.33). CONCLUSIONS Being underweight was associated with an increased risk of mortality in both sexes, and the lowest risk of death was found in males who were slightly overweight with a BMI of 23.0-25.0 kg/m2.

Objectives: The association between long sleep duration and mortality is frequently attributed to the confounding influence of comorbidities. Nevertheless, past efforts to account for comorbidities have yielded inconsistent outcomes. The objective of this study was to evaluate this relationship using a large prospective cohort in Korea. Methods: The study included 114 205 participants from the Health Examinees Study, who were followed for a median of 9.1 years. A composite comorbidity score was developed to summarize the effects of 21 diseases. Using Cox proportional hazards regression, hazard ratios (HRs) and 95% confidence intervals (CIs) for all-cause, cancer, and cardiovascular mortality associated with sleep duration were estimated. These estimates were adjusted for socio-demographic factors, lifestyle factors, body mass index, and comorbidity score. Additionally, a stratified analysis by subgroups with and without comorbidities was conducted. Results: Throughout the follow-up period, 2675 deaths were recorded. After all adjustments, an association was observed between a sleep duration of 8 hours or more and all-cause mortality (HR, 1.10; 95% CI, 1.01 to 1.20). However, no such association was detected in the stratified analysis for the subgroups based on comorbidity status. Conclusions Long sleep duration was found to be associated with all-cause mortality among Koreans, even after adjusting for comorbidities. Additional studies are required to explore the mechanism underlying the association between sleep duration and major causes of mortality.

OBJECTIVES: Lifestyles, including exercise behaviors, change continually over time. This study examined whether the clinical biomarkers (CBs) related to cardiometabolic diseases (CMDs) and their relationships differed with changes in exercise behavior. METHODS: The Ansan-Ansung cohort study (third to fifth phases; n=2,668) was used in the current study. Regular exercise behavior was investigated using a yeso questionnaire. Changes in exercise behavior were classified into 4 groups: Y-N, N-Y, Y-Y, and N-N, with “Y” indicating that a participant regularly engaged in exercise at a given time point and “N” indicating that he or she did not. Fourteen CBs related to CMDs were used, and the associations between changes in exercise behavior and relative changes in CBs were examined. CB networks were constructed and topological comparisons were conducted. RESULTS: Y-N was associated with increases in fasting blood sugar and insulin levels in men, and increased total cholesterol and low-density lipoprotein cholesterol levels in women. Meanwhile, N-Y was inversely associated with body fat percentage, visceral fat percentage, fasting insulin, and triglyceride level. Waist circumference played a central role in most networks. In men, more edges were found in the N-Y and Y-Y groups than in the N-N and Y-N groups, whereas women in the N-Y and Y-Y groups had more edges than those in the N-N and Y-N groups. CONCLUSIONS Consistent exercise or starting to engage in regular exercise had favorable effects on CBs related to CMDs, although their network patterns differed between the sexes.

OBJECTIVES: The purpose of this study was to explore the association between adherence to 2 cancer prevention recommendations and cancer risk. METHODS: In total, 104,386 individuals aged 40-69 years old who were recruited between 2004 and 2013 in the Health Examinees-Gem study were included. Adherence scores were constructed based on 8 items from the World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) cancer prevention recommendations, including body weight, physical activity, diet, alcohol consumption and breastfeeding, and on 6 items from the Korean cancer prevention guidelines (smoking status, eating vegetables and fruits, salty foods, alcohol intake, physical activity, and body weight). A Cox proportional hazards model was used to estimate the associations between adherence scores and the risk of total and 5 major cancers. RESULTS: The multivariable hazard ratio (HR) for total cancer with the high adherence score versus the lowest score (4.25-7.00 vs. 0.00-3.25) for the WCRF/AICR guidelines was 0.91 (95% confidence interval [CI], 0.82 to 1.00) in men. A reduced breast cancer risk was observed among women with the highest score. Men within the highest category of the Korean cancer prevention guideline score (3.25-6.00) had an HR of 0.80 (95% CI, 0.73 to 0.88) for developing total cancer compared to men within the lowest score (0.00-2.50). The higher adherence group among men showed lower risks of developing stomach, colorectal, and lung cancers. CONCLUSIONS Adhering to guidelines for cancer prevention can help to reduce the risk of developing cancer in Korean men. The association might differ by cancer type and gender.

Objectives: We introduced the cohort studies included in the Korean Cohort Consortium (KCC), focusing on large-scale cohort studies established in Korea with a prolonged follow-up period. Moreover, we also provided projections of the follow-up and estimates of the sample size that would be necessary for big-data analyses based on pooling established cohort studies, including population-based genomic studies. Methods: We mainly focused on the characteristics of individual cohort studies from the KCC. We developed “PROFAN”, a Shiny application for projecting the follow-up period to achieve a certain number of cases when pooling established cohort studies. As examples, we projected the follow-up periods for 5000 cases of gastric cancer, 2500 cases of prostate and breast cancer, and 500 cases of non-Hodgkin lymphoma. The sample sizes for sequencing-based analyses based on a 1:1 case-control study were also calculated. Results: The KCC consisted of 8 individual cohort studies, of which 3 were community-based and 5 were health screening-based cohorts. The population-based cohort studies were mainly organized by Korean government agencies and research institutes. The projected follow-up period was at least 10 years to achieve 5000 cases based on a cohort of 0.5 million participants. The mean of the minimum to maximum sample sizes for performing sequencing analyses was 5917-72 102. Conclusions We propose an approach to establish a large-scale consortium based on the standardization and harmonization of existing cohort studies to obtain adequate statistical power with a sufficient sample size to analyze high-risk groups or rare cancer subtypes.

Purpose: Dietary calcium intake has been suggested to be protective against the development of colorectal cancer. The mean dietary calcium intake of Koreans is 490 mg/day, which is far below the recommended calcium intake of 700-800 mg/day. In this study, we explored the relationship between dietary calcium intake and colorectal cancer development in Koreans with relatively low calcium intake compared with individuals in Western countries. Materials and Methods: The Health Examinees Study, a large-scale genomic community-based prospective cohort study, was designed to identify the general characteristics of major chronic diseases in Koreans. A total of 119,501 participants aged 40-69 years recruited between 2004 and 2013 were included in this analysis. The calcium intake level was categorized using the Dietary Reference Intakes for Koreans (KDRIs). The Cox proportional hazards regression model was used to estimate the hazard ratio (HR) and the corresponding 95% confidence intervals (CIs) for colorectal cancer risk, adjusting for potential confounders. Results: In the multivariable-adjusted model, compared with the group that consumed less than the recommended amount of calcium, the group that consumed more than the recommended intake of calcium showed a significant reduction in the risk of colorectal cancer in women. (HR, 0.54; 95% CI, 0.31 to 0.95). Among men, however, no significant association was observed between dietary calcium intake and colorectal cancer risk (HR, 0.89; 95% CI, 0.54 to 1.45). Conclusion Korean women who adhere to the recommended intake of calcium showed a reduced risk of colorectal cancer.

Purpose: This study evaluated the diagnostic performance of contrast-enhanced voiding urosonography (ce-VUS) using a second-generation ultrasound contrast agent for the diagnosis of vesicoureteral reflux (VUR) and intrarenal reflux (IRR), and compared it with that of standard fluoroscopic voiding cystourethrography (VCUG). Methods: Thirty-two consecutive children from April to October 2019 were included in this study. ce-VUS and VCUG were performed simultaneously by two operators with intravesical infusion of a mixture of ultrasound contrast medium, iodinated contrast medium and water. Two pediatric radiologists independently reviewed the ce-VUS and VCUG images and reported the presence and degree of VUR (grades I-V), and the presence and type of IRR. Results: Twenty-seven of 63 urinary systems showed VUR. Interobserver agreement for VUR grading was very good for both examinations (κ=0.87; 95% confidence interval [CI], 0.82 to 0.92 for ce-VUS and κ=0.92; 95% CI, 0.87 to 0.96 for VCUG). The detection rate of VUR showed no significant difference between the two examinations (P=0.370). Four cases of VUR were missed on ce-VUS, while one case of VUR was missed on VCUG. All four false-negative cases on ce-VUS were grade 1 VUR. The two examinations showed very good agreement regarding VUR grading (κ =0.89; 95% CI, 0.81 to 0.96). IRR was more frequently detected with ce-VUS than with VCUG (10 cases with ce-VUS vs. 3 cases with VCUG, P=0.016). Conclusion ce-VUS showed very good agreement with VCUG for detecting grade 2 VUR and above, while grade 1 VUR was sometimes missed with ce-VUS. IRR was more frequently detected with ce-VUS than with VCUG.