Breast cancer has recently become the most common cancer in Korea. Although traditional epidemiological approaches, which are defined as "the study of the distribution and determinants of disease frequency in human population" have increased the understanding of breast cancer development in the human population, it cannot address the importance of the genetic susceptibility of humans to this disease. Therefore, a molecular epidemiological study which uses biological or genetic markers to identify and characterize the disease with the help of advances in molecular biology and human genetics might provide a better understanding of the multi-factorial or multi-step occurrence of human breast cancer. The susceptibility genes involved in the pathogenesis of breast cancer have been categorized into two groups: high penetrance genes (i.e., BRAC1, RB, etc.) and low penetrance genes (i.e., GSTs, XRCC1, etc.). This paper addresses the usefulness of biomarkers in epidemiological research of breast cancer and provides examples of the use of selected low penetrance genes involved in breast carcinogenesis in Korean women. Molecular epidemiological studies of breast cancer have enormous potential in helping researchers understand the gene-environmental interactions involved breast carcinogenesis and provide valuable insights into disease progression and survival.
Biomarkers ; Breast Neoplasms* ; Breast* ; Carcinogenesis ; Disease Progression ; Epidemiologic Studies ; Female ; Genetic Markers ; Genetic Predisposition to Disease ; Genetics, Medical ; Humans ; Korea ; Molecular Biology ; Molecular Epidemiology* ; Penetrance

OBJECTIVE: The purpose of this paper is to analyze the effects of precarious employment status on the level of self-rated health, based on various criteria, by participants in the Korean Labor and Income Panel Survey. METHODS: Data were obtained from 3,268 subjects(2,057 men and 1,211 women), who participated in the 2005-2006 Korean Labor and Income Panel Survey. Group A was classified as Non-precarious employment by both the Ministry of Labor (MoLab) and the Korea Labor and Society Institute (KLSI). The group B was classified as Non-precarious employment by the MoLab and as precarious employment by the KLSI. The group C is classified as Non-precarious employment by both MoLab and KLSI. Outcome variables were self-rated health and a panel logistic regression analysis was performed on the data. RESULTS: The level of self-rated health was worse among group B males (OR: 1.45, C.I:1.00~2.11) and group C males (OR: 1.69, C.I:1.35~2.10) compared to group A males. A substantial difference(57.8%) in the level of self-rated health between groups A and B was attributed to the sociodemographic characteristics of the populations. The difference in self-rated health between groups A and C was explained by work environments(15.7%), as well as by sociodemographic characteristics(26.1%). For female workers, the level of self-rated health in group B and C was worse than in group A, but this finding was not statistically significant. CONCLUSIONS: These findings suggested that the policy to improve the working environment, as well as a more comprehensive effort to reduce the disparity, is needed for the precarious employment worker.
Employment ; Female ; Health Status ; Humans ; Korea ; Logistic Models ; Longitudinal Studies ; Male

OBJECTIVES: The present study was designed to determine the characteristics of shift work and the relationship between shift work and the level of self-rated health using the Korean Labor and Income Panel Study (KLIPS) data, which represents urban households in Korea. METHODS: Using the 9th wave of KLIPS, this study analyzed 2,087 male workers aged 25 to 64 years; participants missing data were excluded from analysis. To determine the impact of shift work on the level of self-rated health, logistic regression analysis was applied that controlled for socio-demographic characteristics, labor environment, and health-related behaviors. RESULTS: Shift workers comprised 13.4% of study subjects overall. The majority(69.2%) of participants were in 2-teams and in 2-shifts. Week 1 shift cycle changes were the highest, 56.3%. The risk of poor self-rated health was not significantly higher among shift workers compared to non-shift workers (OR=1.08, 95% CI=0.79~1.48). When divided by tenure, shift workers with more than 10-years experience (OR=1.79, 95% CI=0.91~3.50) tended to show greater risk than non-shift workers at marginal significance. CONCLUSIONS: In the present study, a significantly higher risk of self-rated poor health among shift workers was not observed. However, shift workers with more than 10-years experience tended to show increased health risk compared to non-shift workers. Further studies are required to determine time-series data and to consider both healthy worker effect and information bias.
Aged ; Bias (Epidemiology) ; Family Characteristics ; Healthy Worker Effect ; Humans ; Korea ; Logistic Models ; Male

PURPOSE: A case-control study was conducted to evaluate the association between diet and breast cancer in Korean women. METHODS: The eligible subjects consisted of a series of histologically confirmed incident breast cancer patients (n= 1063) and non-cancer controls (n=1002) admitted to the departments of surgery at four teaching hospitals located in Seoul, Korea (Seoul National University Hospital, Borame Hospital, Samsung Medical Canter, and Asan medical Center) between 1995 and 2002, from whom blood samples were available. After excluding subjects with a previous history of cancer, hysterectomy or oophorectomy, the final study population consisted of 819 cases and 713 controls. The demographic characteristics and other information were collected by interviewed questionnaire. Dietary information obtained by trained interviewer using food frequency questionnaires. RESULTS: Women educated more than 12 years (OR=1.9, 95% CI: 1.4~2.7), with a higher body mass index (BMI) (OR= 1.4, 95% CI: 1.1~2.0) and a positive family history of breast cancer among the first degree relatives (OR=2.5, 95% CI: 1.3~4.3) were significant risk factors for breast cancer. The longer the exposure to estrogen during their lifetime, the higher the observed risk of breast cancer was (p for trend<0.001). The risk for breast cancer was increased with frequent consumption of cereals (OR=1.8, 95% CI: 1.8~2.5), potatoes (OR=1.8, 95% CI: 1.4~2.5), nuts and seeds (OR=1.9, 95% CI: 1.1~3.4), mushrooms (OR=1.5, 95% CI: 1.2~1.8), meats (OR=1.5, 95% CI: 1.2~1.9), eggs (OR=1.6, 95% CI: 1.1~2.3) and fish (OR=1.5, 95% CI: 1.2~1.9), whereas the risk decreased with higher intakes of green vegetables (OR=0.6, 95% CI: 0.4~1.0), fruits (OR=0.7, 95% CI: 0.6~0.9) and seaweeds (OR=0.7, 95% CI: 0.5~1.0). CONCLUSION: Certain diets (e.g., high fat, high carbohydrate, low vegetable or fruit intake, etc.) were significantly associated with the risk of breast cancer in Korea women, which were similar to the findings in Western countries.
Agaricales ; Body Mass Index ; Breast Neoplasms* ; Breast* ; Case-Control Studies* ; Edible Grain ; Chungcheongnam-do ; Diet* ; Eggs ; Estrogens ; Female ; Fruit ; Hospitals, Teaching ; Humans ; Hysterectomy ; Korea ; Meat ; Nuts ; Ovariectomy ; Ovum ; Surveys and Questionnaires ; Risk Factors ; Seoul ; Solanum tuberosum ; Vegetables

Breast cancer ranks second or third to uterine cervix cancer and stomach cancer as a cause of death in women, and as a common site of primary cancer. The large difference in its incidence between Westernized and non-Westernized countries is remarkable. There is a linear increase with age that is observed in Western countries, which are high-incidence areas, on the contrary to the inverted V shape curve seen in Asian countries. Epidemiologic studies conducted in Korea have shown that an older age, a family history of breast cancer, early menarche, late menopause, late full-term pregnancy, and never having had a breast-fed child are primary risk factors in the development of breast cancer. The estrogen-augmented-by-progesterone hypothesis explains the roles of these factors to some extent. On the other hand, recent molecular studies have revealed the existence of novel gene environmental interactions. Epidemiological features suggest that the breast cancer incidence rate in Korea will increase, but the age specific curve would not be changed in keeping with what is observed in Western countries. Strategies aimed at controlling breast cancer that include the screening guidelines and the identification of individual predispositions may give us further insights into both the etiology and the prevention of breast cancer.
Breast Neoplasms/*epidemiology/physiopathology/prevention & control ; Female ; Humans ; Korea/epidemiology ; Risk Factors

To evaluate the relationship of genetic polymorphisms of ERCC2 and ERCC4 genes, both involved in nucleotide excision repair (NER), and the risk of breast cancer, a hospital-based case-control study was conducted in Korea. Histologically confirmed breast cancer cases (n=574) and controls (n=502) with no present or previous history of cancer were recruited from three teaching hospitals in Seoul during 1995-2001. Information on selected characteristics was collected by interviewed questionnaire. ERCC2 Asp312Asn (G>A) was genotyped by single-base extension assay and ERCC4 Ser835Ser (T>C) by dynamic allele-specific hybridization system. Although no significant association was observed between the genetic polymorphisms and the risk of breast cancer, women with both ERCC2 A allele- and ERCC4 C allele-containing genotypes showed a 2.6-fold risk (95% CI: 1.02-6.48) of breast cancer compared to women concurrently carrying the ERCC2 GG and ERCC4 TT genotypes. The breast cancer risk increased as the number of "at risk" genotypes increased with a borderline significance (P for trend = 0.07). Interactive effect was also observed between ERCC4 genotype and body mass idnex (BMI) for the breast cancer risk; the ERCC4 C allele containing genotypes posed a 1.7-fold (95% CI: 0.96-2.93) breast cancer risk in obese women (BMI>25 kg/m2) with a borderline significance. Our finding suggests that the combined effect of ERCC2 Asp312Asn and ERCC4 Ser835Ser genotypes might be associated with breast cancer risk in Korean women.
Breast Neoplasms/*genetics ; DNA Helicases/*genetics ; DNA-Binding Proteins/*genetics ; Female ; Genetic Predisposition to Disease ; Humans ; Korea ; Middle Aged ; Obesity/*genetics ; *Polymorphism, Genetic ; Transcription Factors/*genetics

OBJECTIVES: The purpose of this study was to examine the associations of childbirth, breastfeeding, and their interaction with breast cancer (BC) risk reduction, and to evaluate the heterogeneity in the BC risk reduction effects of these factors by menopause, hormone receptor (HR) status, and pathological subtype. METHODS: BC patients aged 40+ from the Korean Breast Cancer Registry in 2004-2012 and controls from the Health Examinee cohort participants were included in this study after 1:1 matching (12 889 pairs) by age and enrollment year. BC risk according to childbirth, breastfeeding, and their interaction was calculated in logistic regression models using odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: BC risk decreased with childbirth (3+ childbirths relative to 1 childbirth: OR, 0.66; 95% CI, 0.56 to 0.78 and OR, 0.80; 95% CI, 0.68 to 0.95 in postmenopausal and premenopausal women, respectively); and the degree of risk reduction by the number of children was heterogeneous according to menopausal status (p-heterogeneity=0.04), HR status (p-heterogeneity < 0.001), and pathological subtype (p-heterogeneity < 0.001); whereas breastfeeding for 1-12 months showed a heterogeneous association with BC risk according to menopausal status, with risk reduction only in premenopausal women (p-heterogeneity < 0.05). The combination of 2 more childbirths and breastfeeding for ≥13 months had a much stronger BC risk reduction of 49% (OR, 0.51; 95% CI, 0.45 to 0.58). CONCLUSIONS: This study suggests that the combination of longer breastfeeding and more childbirths reduces BC risk more strongly, and that women who experience both 2 or more childbirths and breastfeed for ≥13 months can reduce their BC risk by about 50%.
Breast Feeding* ; Breast Neoplasms* ; Breast* ; Child ; Cohort Studies ; Female ; Humans ; Logistic Models ; Menopause ; Odds Ratio ; Parturition* ; Population Characteristics ; Risk Reduction Behavior*

Cytochrome P450 1A1 (CYP1A1) is involved in the 2-hydroxylation of estrogen, the hormone that plays a critical role in the etiology of breast carcinoma. We evaluated the associations between two CYP1A1 polymorphisms [MspI (rs4646903); Ile462Val (rs1048943)] and breast cancer in a multicenter case-control study of 513 breast cancer cases and 447 controls in Korea. Women carrying the T allele of the CYP1A1 MspI polymorphism were found to have a 1.72-fold (95% CI 1.11-2.68) greater risk of developing breast cancer. No association was found between any CYP1A1 Ile462Val polymorphism and breast cancer. Haplotype analysis of the two loci showed that the CA haplotype was associated with the lowest risk of breast cancer, and CA/CA diplotypes were associated with a lower risk of breast cancer [OR = 0.28 (0.13-0.61)] than others/others diplotypes. Moreover, this reduced risk was more pronounced among women with a lower body mass index (BMI) [OR = 0.18 (0.06-0.58)] or with a shorter lifetime exposure to estrogen [OR = 0.23 (0.07-0.81)]. The results obtained suggest that the CYP1A1 MspI polymorphisms could affect susceptibility to breast cancer.
Adult ; Aged ; Aged, 80 and over ; Body Mass Index ; Breast Neoplasms/*genetics ; Case-Control Studies ; Cytochrome P-450 CYP1A1/*genetics ; *Disease Susceptibility ; Female ; Haplotypes ; Humans ; Korea ; Middle Aged ; *Polymorphism, Genetic

PURPOSE: To evaluate the potential association between the GSTP1 genotype and the development of breast cancer, a hospital based case-control study was conducted in South Korea. MATERIALS AND METGODS: The study population consisted of 171 histologically confirmed incidents of breast cancer cases, and 171 age-matched controls with no present, or previous, history of cancer. A PCR method was used for the genotyping analyses, and statistical evaluation was performed by an unconditional logistic regression model. RESULTS: No association was observed in the study subjects, or the premenopausal women group with GSTP1 Val allele. However, postmenopausal women with GSTP1 Val allele had a reduced risk of breast cancer (OR=0.3, 95% CI=0.1~0.7). When the data were stratified, by the known risk factors of breast cancer, a significant interaction was observed between the GSTP1 genotype and alcohol consumption (p for interaction = 0.01); women with GSTP1 Val allele, that drank regularly, had a 3.0-fold increased risk of breast cancer (95% CI=1.1~7.9), whereas women with GSTP1 Val allele, that never drink, had protective effects (OR=0.4, 95% CI=0.2~0.8). CONCLUSION: Our findings suggest that GSTP1 Ile105Val polymorphism influences the individual susceptibility to breast cancer, and that this effect may be modified by alcohol consumption.
Alcohol Drinking ; Alleles ; Breast Neoplasms* ; Breast* ; Case-Control Studies ; Female ; Genotype ; Glutathione Transferase* ; Glutathione* ; Humans ; Korea ; Logistic Models ; Polymerase Chain Reaction ; Polymorphism, Genetic* ; Risk Factors

PURPOSE: A hospital-based case-control study was conducted to figure out the risk factors for benign breast disorders in Korea. MATERIALS AND METHODS: Histologically confirmed incident cases of benign breast disorders(n=54) were selected from inpatients with life-style information at the Department of General Surgery, Seoul National University Hospital during 1994 to 1997. Women with free of self-reporting past history of any malignancies were regarded as controls who were selected from the inpatients at the same department of the same hospital(n=180). Information on life-styles including reproductive factors were obtained by direct interview using questionnaire. Adjusted odds ratios and 95% confidence intervals were estimated by multivariate logistic regression model with matching variables. RESULTS: Overall, higher educational level, family history of breast cancer, alcohol drinking, and older age at first fullterm pregnancy related to the risk of benign breast disorders. For premenopausal women, older age, higher educational level, and family history of breast cancer increased the risk of benign breast disorders. For postmenopausal women, alcohol drinking, older age at first fullterm pregnancy, and more frequent experiences of fullterm pregnancy increased the risk. Elder age in postmenopausal women and the experience of breast feeding had, however, protective effect against benign breast disorders. CONCLUSIONS: Although the risk factors for benign breast disease may differ from those for breast cancer, these findings are consistent with the hypothesis of excessive circulating estrogen. The present data indicate some risk factors of benign breast disorders are confirmed as risk factors for breast cancer though a substantial agreement between the risk factors for (pathologically confirmed) benign and malignant breast disease.
Alcohol Drinking ; Breast Diseases ; Breast Feeding ; Breast Neoplasms ; Breast* ; Case-Control Studies* ; Estrogens ; Female ; Humans ; Inpatients ; Korea* ; Logistic Models ; Odds Ratio ; Pregnancy ; Reproduction ; Risk Factors* ; Seoul ; Surveys and Questionnaires