OBJECTIVES: To explore the possible effect of an interaction between summertime heat waves and ozone on cardiopulmonary mortality during the 1994 heat wave in Korea. METHODS: The unusually hot summer of 1994 in Korea was defined as the heat wave in this study. We examined the associations of air pollutants with daily cardiopulmonary deaths between 1991-1995, considering the product term of the heat wave and each pollutant, weather and time trends. RESULTS: During the heat wave, while temperatures were uniformly higher than those of other summers, the within-heat-wave difference in mortality paralleled that in the regional ozone levels. In terms of the influence of the heat wave, the results of ozone were different to those of total suspended particles (TSP) and sulfur dioxide (SO2). The ozone association (relative risk (RR) =1.036; 95% confidence interval (CI) = 1.018-1.054) was observed only under heat wave conditions, while the TSP (RR =1.006, 95% CI = 0.999-1.012) and the SO2 (RR =1.018, 95% CI = 1.011-1.024) associations were found under normal weather conditions (per interquartile increase of each pollutant; results of three pollutants model). The ozone association under heat wave was attributable to the statistical interaction between the heat wave and ozone. CONCLUSIONS: These results support the possibility of a biological synergy between the heat wave and ozone, one that is not evident between the heat wave and other major pollutants like particles or SO2.
Air Pollutants ; Air Pollution ; Hot Temperature* ; Infrared Rays* ; Korea* ; Mortality* ; Ozone* ; Sulfur Dioxide ; Weather

We conducted a community-based cross-sectional study to evaluate the role of genetics in determining the individual difference in total testosterone and sex hormone-binding globulin levels. Study participants comprised 730 Korean men consisting of 142 pairs of monozygotic twins, 191 pairs of siblings, and 259 father-offspring pairs from 270 families who participated in the Healthy Twin study. Serum concentration of total testosterone and sex hormone-binding globulin were measured by chemiluminescence immunoassay, and free testosterone and bioavailable testosterone were calculated using Vermeulen's method. Quantitative genetic analysis based on a variance decomposition model showed that the heritability of total testosterone, free testosterone, bioavailable testosterone, and sex hormone-binding globulin were 0.56, 0.45, 0.44, and 0.69, respectively after accounting for age and body mass index. Proportions of variance explained by age and body mass index varied across different traits, from 8% for total testosterone to 31% for sex hormone-binding globulin. Bivariate analysis showed a high degree of additive genetic correlation (ρG = 0.67) and a moderate degree of individual-specific environmental correlation (ρE = 0.42) between total testosterone and sex hormone-binding globulin. The findings confirmed the important role of genetics in determining the individually different levels of testosterone and sex hormone-binding globulin during adulthood in Korean men as found in non-Asian populations, which may suggest that common biologic control for determining testosterone level directly or indirectly through binding protein are largely shared among different populations.

Focusing on complex diseases of public health significance, strategic issues regarding the on-going Korean Genome Cohort were reviewed: target size and diseases, measurements, study design issues, and followup strategy of the cohort. Considering the epidemiologic characteristics of Korean population as well as strengths and drawbacks of current research environment, we tried to tailor the experience of other existing cohorts into proposals for this Korean study. Currently 100,000 individuals have been participating the new Genome Cohort in Korea. Target size of de novo collection is recommended to be set as between 300,000 to 500,000. This target size would allow acceptable power to detect genetic and environmental factors of moderate effect size and possible interactions between them. Family units and/or special subgroups are recommended to parallel main body of adult individuals to increase the overall efficiency of the study. Given that response rate to the conventional re-contact method may not be satisfactory, successful follow-up is the main key to the achievement of the Korean Genome Cohort. Access to the central database such as National Health Insurance data can provide enormous potential for near-complete case detection. Efforts to build consensus amongst scientists from broad fields and stakeholders are crucial to unleash the centralized database as well as to refine the commitment of this national project.
Public Health ; Population Surveillance ; Mortality/trends ; Male ; Korea ; Humans ; *Genome, Human ; *Genetic Predisposition to Disease ; Female ; Epidemiologic Studies ; Cohort Studies

The Korean Twin Register (n=154,783 pairs) was reported in 2002 as the first nationwide twin study in Korea and the largest study in Asia. The Twin Register has the information of disease outcomes since 1990, and basic clinical and questionnaire data from biennial health examination provided by Korea National Health Service. The author attempted to calculate some of the genetic parameters of cancers in this population. Common cancers in Korea known to have familial aggregation (colon and breast) and cancers of which familial aggregation is unclear (stomach cancer) were examined for their familial recurrence risks. There were 699 stomach cancers, 438 breast and 491 colorectal cancers cases in the twin register between 1991 and 2003. Like-sex twins showed recurrence risks (lambdaLS) of 5.1 (95% CI 3.7 - 6.9) for stomach cancers, 15.5 (95% CI 10.9-20.2) for female breast cancers, and 28.1 (95% CI 23.5-34.4) for colon cancers. Colorectal cancers of female like-sex twins show significantly higher familial recurrence risk 40.7 (95% CI 34.6-47.4), suggesting higher genetic contribution in women than in men. The results show increased familial risks compared with previous studies from the same register and are largely compatible with other studies. The data of the Twin Register could be used for estimating population level genetic parameters, as well as base of the various studies.
Asia ; Breast ; Colonic Neoplasms ; Colorectal Neoplasms ; Female ; Humans ; Korea* ; Male ; Molecular Epidemiology* ; National Health Programs ; Recurrence ; Stomach Neoplasms ; Twins* ; Surveys and Questionnaires

Background: While evidence shows a tendency toward delays in menopause worldwide, whether prevalence of premature (< 40 years) or early menopause (40–44 years) is also reduced in different ethnic groups is uncertain. The aim of this study was to explore birth cohort effect in the prevalence of premature and early menopause in United States (US) and Korea. Methods: This is a retrospective study using the National Health and Nutrition Examination Survey (NHANES, 1999–2014) and the Korea NHANES (KNHANES, 2007–2012). We analyzed prevalence of premature and early menopause in three ethnic groups of US and Korea. We restricted our analysis to women aged ≥ 45 years at the time of the survey born between 1920 and 1969. The data of both eligible 9,209 US women and 9,828 Korean was included in final analysis. We calculated odds ratios (OR) for each outcome adjusting for biological and socioeconomic factors, respectively. Results: Prevalence of premature menopause was 1.7% in US, 2.8% in Korean women. Early menopause occurred in 3.4% and 7.2% of US and Korean, respectively. In US women, prevalence of premature and early menopause did not change and did not differ across three ethnicities. Korean women showed highest and consistently decreasing prevalence (P < 0.001). When we adjusted for covariates, birth lower risk for premature menopause was evident in US Non-Hispanic black born in 1950s and in Korean born between 1940s and 1960s compared to those born in 1920s. In the analysis of early menopause, excluding premature menopause patients, lower risk of more recent generation (born in 1940s and later) was evident in Korean women. Conclusion The trend and birth cohort effect in occurrence of premature and early menopause among the US and Korea women are different. Prevalences of premature and early menopause decrease only in Korean.

Background: While evidence shows a tendency toward delays in menopause worldwide, whether prevalence of premature (< 40 years) or early menopause (40–44 years) is also reduced in different ethnic groups is uncertain. The aim of this study was to explore birth cohort effect in the prevalence of premature and early menopause in United States (US) and Korea. Methods: This is a retrospective study using the National Health and Nutrition Examination Survey (NHANES, 1999–2014) and the Korea NHANES (KNHANES, 2007–2012). We analyzed prevalence of premature and early menopause in three ethnic groups of US and Korea. We restricted our analysis to women aged ≥ 45 years at the time of the survey born between 1920 and 1969. The data of both eligible 9,209 US women and 9,828 Korean was included in final analysis. We calculated odds ratios (OR) for each outcome adjusting for biological and socioeconomic factors, respectively. Results: Prevalence of premature menopause was 1.7% in US, 2.8% in Korean women. Early menopause occurred in 3.4% and 7.2% of US and Korean, respectively. In US women, prevalence of premature and early menopause did not change and did not differ across three ethnicities. Korean women showed highest and consistently decreasing prevalence (P < 0.001). When we adjusted for covariates, birth lower risk for premature menopause was evident in US Non-Hispanic black born in 1950s and in Korean born between 1940s and 1960s compared to those born in 1920s. In the analysis of early menopause, excluding premature menopause patients, lower risk of more recent generation (born in 1940s and later) was evident in Korean women. Conclusion The trend and birth cohort effect in occurrence of premature and early menopause among the US and Korea women are different. Prevalences of premature and early menopause decrease only in Korean.

Rheumatoid arthritis (RA) is a chronic autoimmune disorder that is characterized by inflammation of the synovial tissue and deterioration of the joint and bone. A recent study reported a potential gene-environment interaction between HLA-DR and smoking. The present study investigated whether a specific gene was related to the association between smoking and the severity of RA (rheumatoid factor levels > 20 IU/ml). We used the resources of the NARAC family collection of GAW 15 databases, and 1139 subjects with RF > 20 IU/ml were included in the current analysis. The linkage panel contained 5858 SNP markers, and 5744 SNPs passed quality control criteria. Linear regression analyses, using PLINK software and generalized estimating equation regression models, were used to test for associations between the SNPs and the severity of RA according to smoking groups. Two major findings were established. First, the severity of RA in smokers was associated with rs703618 (p=6x10(-5)), which lies in the intronic region of the stabilin 2 (STAB2) gene on chromosome 12. Second, there were significant differences in the levels of RF between 'ever smokers' and 'never smokers' according to the rs703618 genotype (G/G, A/G, A/A). We investigated whether a specific gene acts as a mediator between smoking and the severity of RA and found that the STAB2 gene could affect this relationship. Our finding indicates that smoking may mediate RA severity by affecting the expression level of a specific gene.
Arthritis ; Arthritis, Rheumatoid ; Chromosomes, Human, Pair 12 ; Gene-Environment Interaction ; Genotype ; HLA-DR Antigens ; Humans ; Hyaluronic Acid ; Inflammation ; Introns ; Joints ; Linear Models ; Polymorphism, Single Nucleotide ; Quality Control ; Smoke ; Smoking

PURPOSE: We aimed to examine if past and more recent body mass index (BMI) changes are associated with eating behavior (EB) traits and whether these associations are due to non-genetic factors. MATERIALS AND METHODS: In 1321 Korean twins and family members, recent and past BMI change groups were defined using quartiles of BMI change between first and second visits over 2.4+/-0.9 years and BMI change between 20 years old and second visit, respectively. We applied linear mixed analysis for relationships of past or recent BMI change groups and each EB (restrained, external, and emotional EB using the Dutch Eating Behavior Questionnaire) assessed at second visit after adjusting for household effect and covariates (age, gender, education, medical history of diabetes, hypertension, and dyslipidemia, alcohol use, physical activity, smoking habit, and calorie intake). In monozygotic twin pairs, paired t-test for within-pair comparison and conditional logistic regression analysis were conducted regarding EB. RESULTS: Greater past BMI change was associated with higher restrained eating scores (P for trend=0.031), whereas greater recent BMI change was associated with higher external eating scores (P for trend=0.046). In co-twin-control analysis, twins with greater past BMI change were more likely to have higher restrained eating scores as compared with their co-twins with lower past BMI change (odds ratio 1.80; 95% confidence interval 1.13-2.87), whereas there were no associations between recent BMI change and external eating scores. CONCLUSION: Greater BMI change since 20 years old is associated with higher dietary restraint, and non-genetic factors explain this relationship.
Adult ; Aged ; Body Composition/physiology ; *Body Mass Index ; Body Weight/physiology ; Feeding Behavior/*physiology ; Female ; Humans ; Male ; Middle Aged ; Questionnaires ; Twins, Monozygotic

OBJECTIVES: This study aimed to evaluate whether the birth rate is associated with socioeconomic status in the women of the Republic of Korea, where the birth rate is rapidly decreasing. METHODS: This study included 732 females from the Healthy Twin Study, a family-twin cohort. The participants were classified into 3 socioeconomic groups according to their average income, education, and occupation. The association between socioeconomic status and number of children was assessed using gamma regression analysis with a generalized linear mixed model, adjusting for the age group, smoking/alcohol status, and family relationships. RESULTS: The group with the highest education level had significantly fewer children compared with the group with the lowest education level (p=0.004). However, no significant associations were found according to household income level. The non-manual labor group had significantly fewer children compared with those working as homemakers (p=0.008). CONCLUSIONS: This study aimed to explain the causal relationship between socioeconomic status and number of children. Associations between some socioeconomic status and number of children were found in Korea.
Adult ; Aged ; Alcohol Drinking ; Asian Continental Ancestry Group ; *Birth Rate ; Child ; Cohort Studies ; Family Relations ; Female ; Humans ; Income ; Middle Aged ; Occupations ; Regression Analysis ; Republic of Korea ; Smoking ; Socioeconomic Factors ; Twins ; Women/*psychology

OBJECTIVES: We investigated the clustering of selected lifestyle factors (cigarette smoking, heavy alcohol consumption, lack of physical exercise) and identified the population characteristics associated with increasing lifestyle risks. METHODS: Data on lifestyle risk factors, sociodemographic characteristics, and history of chronic diseases were obtained from 7,694 individuals > or =20 years of age who participated in the 2005 Korea National Health and Nutrition Examination Survey (KNHANES). Clustering of lifestyle risks involved the observed prevalence of multiple risks and those expected from marginal exposure prevalence of the three selected risk factors. Prevalence odds ratio was adopted as a measurement of clustering. Multiple correspondence analysis, Kendall tau correlation, Man-Whitney analysis, and ordinal logistic regression analysis were conducted to identify variables increasing lifestyle risks. RESULTS: In both men and women, increased lifestyle risks were associated with clustering of: (1) cigarette smoking and excessive alcohol consumption, and (2) smoking, excessive alcohol consumption, and lack of physical exercise. Patterns of clustering for physical exercise were different from those for cigarette smoking and alcohol consumption. The increased unhealthy clustering was found among men 20-64 years of age with mild or moderate stress, and among women 35-49 years of age who were never-married, with mild stress, and increased body mass index (>30 kg/m2). CONCLUSIONS: Addressing a lack of physical exercise considering individual characteristics including gender, age, employment activity, and stress levels should be a focus of health promotion efforts.