Cancer risk among air transportation industry workers in Korea: a national health registry-based study.

BACKGROUND: Flight attendants face various risk factors in their working environments, particularly occupational exposure to cosmic radiation. This study aimed to assess cancer risk among air transportation industry workers, including flight attendants, in Korea by constructing a cohort using national health registry-based data and analyzing cancer incidence risk. METHODS: We used the Korea National Health Insurance Service database from 2002 to 2021 to construct a cohort of 37,011 workers in the air transportation industry. Cancer incidence was defined using the tenth version of the International Classification of Diseases. We calculated the age- and sex-specific standardized incidence ratios (SIRs) and 95% confidence intervals (CIs) by applying the cancer incidence rate of the general population between 2002 and 2019. RESULTS: Approximately 5% of the cohort developed cancer. Overall, the cancer incidence in the cohort was similar to or lower than that of the general population, with the SIRs for all cancers being lower. However, significantly higher SIRs were observed for nasopharyngeal cancer (SIR, 3.21; 95% CI, 1.71-5.48) and non-Hodgkin lymphoma (SIR, 1.57; 95% CI, 1.02-2.32) in male workers and breast and genital cancer (SIR, 1.51; 95% CI, 1.34-1.70) and thyroid cancer (SIR, 1.25; 95% CI, 1.05-1.47) in female workers. CONCLUSIONS: The lower overall cancer incidence among air transportation industry workers observed in this study could indicate the "healthy worker effect"; however, the incidences of certain cancers were higher than those in the general population. Given that these workers are exposed to multiple occupational and lifestyle-related risk factors, including cosmic radiation, further studies are necessary to determine radiation-induced cancer risk while considering potential confounding factors.

Associations Between Gestational Weight Gain, Gestational Diabetes, and Childhood Obesity Incidence.

INTRODUCTION: Excessive maternal gestational weight gain (GWG) is strongly correlated with childhood obesity, yet how excess maternal weight gain and gestational diabetes mellitus (GDM) interact to affect early childhood obesity is poorly understood. The purpose of this study was to investigate whether overall and trimester-specific maternal GWG and GDM were associated with obesity in offspring by age 6 years. METHODS: A cohort of 10,335 maternal-child dyads was established from electronic health records. Maternal weights at conception and delivery were estimated from weight trajectory fits using functional principal components analysis. Kaplan-Meier curves and Cox regression, together with generalized raking, examined time-to-childhood-obesity. RESULTS: Obesity diagnosed prior to age 6 years was estimated at 19.7% (95% CI: 18.3, 21.1). Maternal weight gain during pregnancy was a strong predictor of early childhood obesity (p < 0.0001). The occurrence of early childhood obesity was lower among mothers with GDM compared with those without diabetes (adjusted hazard ratio = 0.58, p = 0.014). There was no interaction between maternal weight gain and GDM (p = 0.55). Higher weight gain during the first trimester was associated with lower risk of early childhood obesity (p = 0.0002) whereas higher weight gain during the second and third trimesters was associated with higher risk (p < 0.0001). DISCUSSION: Results indicated total and trimester-specific maternal weight gain was a strong predictor of early childhood obesity, though obesity risk by age 6 was lower for children of mothers with GDM. Additional research is needed to elucidate underlying mechanisms directly related to trimester-specific weight gain and GDM that impede or protect against obesity prevalence during early childhood.

Excessive maternal gestational weight gain (GWG) and gestational diabetes mellitus (GDM) have been linked to childhood obesity. Yet, research on how excessive total and trimester-specific GWG and GDM interact to affect early childhood obesity remains inconclusive. This study found that inadequate weight gain in the first trimester and excessive weight gain in the second and third trimester were associated with higher risks of childhood obesity by age 6. No significant interaction between maternal GWG and GDM was noted suggesting that these two important maternal conditions do not have a combined effect on the risk of early childhood obesity.

Prognostic value of CA125 kinetics, half-life, and nadir in the treatment of epithelial ovarian cancer: a systematic review and meta-analysis.

OBJECTIVE: To investigate the prognostic value of cancer antigen 125 (CA125) related variables on progression free survival and overall survival in primary and recurrent ovarian cancers. METHOD: A comprehensive review of the Medline, Embase, and Cochrane Library databases was conducted to identify relevant literature on survival outcomes according to the ELIMination Rate Constant K (KELIM), Gynecologic Cancer InterGroup (GCIG) CA125 response criteria, CA125 half-life, and CA125 nadir levels during first line or later line chemotherapy. The search included articles published before February 2023. Cut-off values determining the favorable/unfavorable score of each study were extracted, and pooled hazard ratios (HRs) and 95% confidence intervals (CIs) were analyzed using a random effects model to identify the relationship between survival outcomes of the favorable/unfavorable groups, which was determined by an individual model using CA125 kinetics. RESULTS: A total of 27 studies with 14 444 patients with epithelial ovarian cancer were included in this meta-analysis. In primary ovarian cancer, a favorable KELIM score, determined by individual modeled cut-off values, was associated with a significant progression free survival (HR 0.53, 95% CI 0.45 to 0.62) and overall survival (HR 0.51, 95% CI 0.43 to 0.62) benefit in the primary setting. The favorable KELIM scored group also correlated with a better progression free survival (HR 0.54, 95% CI 0.47 to 0.62) in relapsed disease. We failed to demonstrate a better prognostic value of the GCIG response criteria and the CA125 half-life for progression free survival and overall survival. CONCLUSION: Novel chemotherapy response scores, such as KELIM, may be more clinically relevant than other prognostic models using CA125 kinetics, being directly associated with a more favorable survival in both the primary and relapsed setting in patients with epithelial ovarian cancer. STUDY REGISTRATION: The systemic review and meta-analysis were registered in PROSPERO (CRD42023385512).

Weight Changes and Unhealthy Weight Control Behaviors Are Associated With Dysmenorrhea in Young Women.

BACKGROUND: This study aimed to evaluate the prevalence of dysmenorrhea and to investigate the effect of weight changes or unhealthy weight control behaviors on dysmenorrhea in young Korean women. METHODS: We used large-scale data of women, aged 14 to 44 years, who participated in the Korean Study of Women's Health-Related Issues. Dysmenorrhea was measured using a visual analog scale and was categorized as none, mild, moderate, and severe according to the severity. Weight changes and unhealthy weight control behaviors (any of the behaviors, fasting/meal skipping, drugs, the use of unapproved dietary supplements, and one-food diets) over the past year were self-reported. We used multinomial logistic regression to investigate the association between weight changes or unhealthy weight control behaviors and dysmenorrhea. RESULTS: Of the 5,829 young women participating in the study, 5,245 (90.0%) participants experienced dysmenorrhea [2,184 (37.5%) had moderate and 1,358 (23.3%) had severe]. After adjusting for confounders, the odds ratios for moderate and severe dysmenorrhea in participants with weight changes ≥ 3 kg (vs. < 3 kg) were 1.19 (95% confidence interval: 1.05-1.35) and 1.25 (95% confidence interval: 1.08-1.45), respectively. The odds ratios in participants with any unhealthy weight control behaviors were 1.22 (95% confidence interval: 1.04-1.42) and 1.41 (95% confidence interval: 1.19-1.67) for those with moderate and severe dysmenorrhea, respectively. CONCLUSION: Weight changes (≥ 3 kg) or unhealthy weight control behaviors are common among young women, which may adversely affect dysmenorrhea. Therefore, attention needs to be paid to excessive weight changes and unhealthy weight control behaviors to improve dysmenorrhea in young women.

Multiwave validation sampling for error-prone electronic health records.

Electronic health record (EHR) data are increasingly used for biomedical research, but these data have recognized data quality challenges. Data validation is necessary to use EHR data with confidence, but limited resources typically make complete data validation impossible. Using EHR data, we illustrate prospective, multiwave, two-phase validation sampling to estimate the association between maternal weight gain during pregnancy and the risks of her child developing obesity or asthma. The optimal validation sampling design depends on the unknown efficient influence functions of regression coefficients of interest. In the first wave of our multiwave validation design, we estimate the influence function using the unvalidated (phase 1) data to determine our validation sample; then in subsequent waves, we re-estimate the influence function using validated (phase 2) data and update our sampling. For efficiency, estimation combines obesity and asthma sampling frames while calibrating sampling weights using generalized raking. We validated 996 of 10,335 mother-child EHR dyads in six sampling waves. Estimated associations between childhood obesity/asthma and maternal weight gain, as well as other covariates, are compared to naïve estimates that only use unvalidated data. In some cases, estimates markedly differ, underscoring the importance of efficient validation sampling to obtain accurate estimates incorporating validated data.

Testing Linear Operator Constraints in Functional Response Regression with Incomplete Response Functions.

Hypothesis testing procedures are developed to assess linear operator constraints in function-on-scalar regression when incomplete functional responses are observed. The approach enables statistical inferences about the shape and other aspects of the functional regression coefficients within a unified framework encompassing three incomplete sampling scenarios: (i) partially observed response functions as curve segments over random sub-intervals of the domain; (ii) discretely observed functional responses with additive measurement errors; and (iii) the composition of former two scenarios, where partially observed response segments are observed discretely with measurement error. The latter scenario has been little explored to date, although such structured data is increasingly common in applications. For statistical inference, deviations from the constraint space are measured via integrated L 2 -distance between the model estimates from the constrained and unconstrained model spaces. Large sample properties of the proposed test procedure are established, including the consistency, asymptotic distribution and local power of the test statistic. Finite sample power and level of the proposed test are investigated in a simulation study covering a variety of scenarios. The proposed methodologies are illustrated by applications to U.S. obesity prevalence data, analyzing the functional shape of its trends over time, and motion analysis in a study of automotive ergonomics.

Responses to COVID-19 Threats: an Evolutionary Psychological Analysis.

Responses to COVID-19 public health interventions have been lukewarm. For example, only 64% of the US population has received at least two vaccinations. Because most public health interventions require people to behave in ways that are evolutionarily novel, evolutionary psychological theory and research on mismatch theory, the behavioral immune system, and individual differences can help us gain a better understanding of how people respond to public health information. Primary sources of threat information during the pandemic (particularly in early phases) were geographic differences in morbidity and mortality statistics. We argue that people are unlikely to respond to this type of evolutionarily novel information, particularly under conditions of high uncertainty. However, because individual differences affect threat perceptions, some individual differences will be associated with threat responses. We conducted two studies (during Phase 1 and 2 years later), using data from primarily public sources. We found that state-level COVID-19 morbidity and mortality rates had no relationship with mental health symptoms (an early indicator of how people were responding to the pandemic), suggesting that people-in general-were not attending to this type of information. This result is consistent with the evolutionary psychological explanation that statistical information is likely to have a weak effect on the behavioral immune system. We also found that individual differences (neuroticism, IQ, age, and political ideology) affected how people responded to COVID-19 threats, supporting a niche-picking explanation. We conclude with suggestions for future research and suggestions for improving interventions and promoting greater compliance.

Insufficient weight management in pregnant women with gestational diabetes mellitus.

OBJECTIVES: This study investigated whether weight was managed appropriately in pregnant women with gestational diabetes mellitus (GDM) and examined the association between insufficient gestational weight gain (GWG) and adverse pregnancy outcomes. METHODS: The study included 235 pregnant women with GDM from the Korean Pregnancy Outcome Study. GWG from the second to the third trimester (kg/wk) and total GWG (kg) were classified as insufficient, appropriate, or excessive according to the 2009 Institute of Medicine guidelines. Adverse pregnancy outcomes included maternal (hypertensive disorders of pregnancy, preterm birth, cesarean delivery, and delivery complications) and infant (low birth weight, high birth weight, neonatal intensive care unit admission, and congenital anomalies) outcomes. RESULTS: The proportion of pregnant women with GDM who had insufficient GWG from the second to the third trimester was 52.3%, and that of participants with total insufficient GWG was 48.1%. There were no significant associations between insufficient GWG from the second to the third trimester and adverse pregnancy outcomes. Participants with total insufficient GWG had a significantly lower risk of preterm birth (odds ratio [OR], 0.17; 95% confidence interval [CI], 0.05-0.60) and high birth weight (OR, 0.23; 95% CI, 0.07-0.80). CONCLUSION: Our findings suggest the importance of appropriate weight management and the need for GWG guidelines for pregnant women with GDM.

New-Onset and Exacerbation of Lung Diseases after Short-Term Exposures to Humidifier Disinfectant during Hospitalization.

(1) Background: Humidifier disinfectant (HD) is a biocidal chemical to keep the water tank inside a humidifier clean. Thousands of Koreans have experienced HD-related lung injuries. Of them, 6.9% were exposed to HD in hospitals. (2) Methods: This study investigated changes of diseases in patients (or caregivers) who experienced HD exposures during hospitalization and also investigated characteristics of hospital exposure using data from all HD-related lung injury enrollment in Korea. (3) Results: Of a total of 162 subjects, 139 subjects were hospitalized for non-lung diseases, and 23 people were hospitalized for lung diseases at the time of hospitalization. During hospital exposure, 99 (71.2%) of those hospitalized with non-lung disease experienced a new-onset of lung disease, and 15 (65.2%) of those hospitalized with lung diseases experienced exacerbation of their existing lung diseases. When we compared their exposure characteristics, those exposed in hospitals (vs. non-hospital, mostly home) were exposed for shorter periods, at closer distances, at higher HD indoor concentrations, constantly all day, and directly in the facial direction. (4) Conclusion: In conclusion, HD exposures in hospital with a high intensity even for a short term were associated with new-onset or exacerbation of lung diseases. Our findings suggest that acute exposures to HD can cause lung diseases.

Environmental exposures to lead, cadmium, and mercury and pterygium in Korean adults.

Pterygium, one of the most common eye disorders, is an abnormal fibrovascular proliferation extending from the conjunctiva to the cornea. The mechanism of development in pterygium has not been fully elucidated; however, oxidative stress is suggested to be one of the major causes. Heavy metals such as lead (Pb), cadmium (Cd), and mercury (Hg) enter the human body and induce oxidative stress. However, no study has investigated the association of these heavy metals with pterygium. Therefore, this study aimed to evaluate the associations of environmental exposures to Pb, Cd, and Hg with pterygium in the Korean general adults. We analyzed data from 6,587 adults (≥ 20 years of age) who participated in the Korea National Health and Nutrition Examination Survey (KNHANES) 2008-2011. Pterygium was diagnosed as the presence of a wing-shaped fibrovascular growth. The exposures of Pb, Cd, and Hg were estimated by measuring blood concentrations. The prevalence of pterygium in this study population was 4.0% (348 subjects). After adjusting for potential confounders, the Pb level in blood was found to have a significant dose-dependent association with pterygium (p for trend = 0.001), and its highest quintile (vs. the lowest) had an odds ratio (OR) of 2.22 (95% CI: 1.30, 3.78) for pterygium. The Hg level in blood in the second quintile (vs. the lowest) had an OR of 1.64 (95% CI: 1.04, 2.59) for pterygium. In conclusion, this study suggests that environmental exposures to Pb and Hg in the Korean general adults may be related to the development of pterygium.

Minnesota Multiphasic Personality Inventory-Adolescent-Restructured Form (MMPI-A-RF) characteristics of ADHD in a Korean psychiatric sample.

Global rates of attention-deficit/hyperactivity disorder (ADHD) have risen. In Korea, ADHD is associated with functional impairments and comorbidity with other psychological disorders. This study examined the correlates of ADHD in a psychiatric sample of Korean adolescents on the Minnesota Multiphasic Personality Inventory-Adolescent-Restructured Form (MMPI-A-RF). In a clinical sample of 247 adolescents, MMPI-A-RF scores from 46 patients diagnosed with ADHD were compared to the remainder of the clinical sample and to the Korean MMPI-A-RF norms. Results demonstrated significantly different scores for the ADHD group on scales indicating externalizing concerns and behavior dysfunction compared with the clinical group with other disorders and to a normative sample. Notable differences were also observed between clinical groups on scales reflecting interpersonal functioning. Relative risk ratio analyses demonstrated that an MMPI-A-RF T-score of 55 was generally most effective for predicting risk for an ADHD diagnosis in the clinical sample.

Combining multiple imputation with raking of weights: An efficient and robust approach in the setting of nearly true models.

Multiple imputation (MI) provides us with efficient estimators in model-based methods for handling missing data under the true model. It is also well-understood that design-based estimators are robust methods that do not require accurately modeling the missing data; however, they can be inefficient. In any applied setting, it is difficult to know whether a missing data model may be good enough to win the bias-efficiency trade-off. Raking of weights is one approach that relies on constructing an auxiliary variable from data observed on the full cohort, which is then used to adjust the weights for the usual Horvitz-Thompson estimator. Computing the optimally efficient raking estimator requires evaluating the expectation of the efficient score given the full cohort data, which is generally infeasible. We demonstrate MI as a practical method to compute a raking estimator that will be optimal. We compare this estimator to common parametric and semi-parametric estimators, including standard MI. We show that while estimators, such as the semi-parametric maximum likelihood and MI estimator, obtain optimal performance under the true model, the proposed raking estimator utilizing MI maintains a better robustness-efficiency trade-off even under mild model misspecification. We also show that the standard raking estimator, without MI, is often competitive with the optimal raking estimator. We demonstrate these properties through several numerical examples and provide a theoretical discussion of conditions for asymptotically superior relative efficiency of the proposed raking estimator.

Evaluating the Measurement Invariance of MMPI-2-RF Restructured Clinical Scale 4 (Antisocial Behavior) between American and Korean Clinical Samples: Exploring Cultural and Translation Issues Affecting Item Responding.

Establishing the cross-cultural measurement invariance of psychometric scales is considered an essential step before scale means are compared across cultures. Although the MMPI instruments have been extensively researched, few studies have examined the measurement equivalence of MMPI scales in cross-cultural research. This study examined the measurement invariance of MMPI-2-RF Restructured Clinical Scale 4 (RC4; Antisocial Behavior) using multi-group confirmatory factor analysis with American and Korean clinical samples by (a) comparing a rationally-derived four-factor model (School Problems, Substance Abuse, Family Problems, and Violation of Social Norms) with a one-factor model, and (b) examining the measurement invariance of the RC4 four-factor model. After adjusting for age and gender, partial scalar invariance was achieved, and six non-invariant items were identified, most of which centered around substance abuse. Results support the generalizability of the four factors across cultures; however, special attention is needed when using substance abuse items with Korean clinical populations. Plausible sources of item non-invariance were explored in the context of translation challenges and observed patterns of relationship with external measures.

Two-phase analysis and study design for survival models with error-prone exposures.

Increasingly, medical research is dependent on data collected for non-research purposes, such as electronic health records data. Health records data and other large databases can be prone to measurement error in key exposures, and unadjusted analyses of error-prone data can bias study results. Validating a subset of records is a cost-effective way of gaining information on the error structure, which in turn can be used to adjust analyses for this error and improve inference. We extend the mean score method for the two-phase analysis of discrete-time survival models, which uses the unvalidated covariates as auxiliary variables that act as surrogates for the unobserved true exposures. This method relies on a two-phase sampling design and an estimation approach that preserves the consistency of complete case regression parameter estimates in the validated subset, with increased precision leveraged from the auxiliary data. Furthermore, we develop optimal sampling strategies which minimize the variance of the mean score estimator for a target exposure under a fixed cost constraint. We consider the setting where an internal pilot is necessary for the optimal design so that the phase two sample is split into a pilot and an adaptive optimal sample. Through simulations and data example, we evaluate efficiency gains of the mean score estimator using the derived optimal validation design compared to balanced and simple random sampling for the phase two sample. We also empirically explore efficiency gains that the proposed discrete optimal design can provide for the Cox proportional hazards model in the setting of a continuous-time survival outcome.

Methodological and statistical advances in the consideration of cultural diversity in assessment: A critical review of group classification and measurement invariance testing.

One of the most important considerations in psychological and educational assessment is the extent to which a test is free of bias and fair for groups with diverse backgrounds. Establishing measurement invariance (MI) of a test or items is a prerequisite for meaningful comparisons across groups as it ensures that test items do not function differently across groups. Demonstration of MI is particularly important in assessment settings where test scores are used in decision making. In this review, we begin with an overview of test bias and fairness, followed by a discussion of issues involving group classification, focusing on categorizations of race/ethnicity and sex/gender. We then describe procedures used to establish MI, detailing steps in the implementation of multigroup confirmatory factor analysis, and discussing recent developments in alternative procedures for establishing MI, such as the alignment method and moderated nonlinear factor analysis, which accommodate reconceptualization of group categorizations. Lastly, we discuss a variety of important statistical and conceptual issues to be considered in conducting multigroup confirmatory factor analysis and related methods and conclude with some recommendations for applications of these procedures. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

A comparative evaluation of Korean MMPI-A and MMPI-A-RF Substance Abuse Scales.

OBJECTIVE: The purpose of the present study was to compare psychometric properties of the Substance Abuse (SUB) Scale on the Korean Minnesota Multiphasic Personality Inventory-Adolescent-Restructured Form (MMPI-A-RF) with those on the Korean MMPI-A (the Alcohol/Drug Problem Acknowledgment Scale [ACK]), the Alcohol/Drug Problem Proneness Scale [PRO], and the MacAndrew Alcoholism Scale-Revised Scale [MAC-R]). METHOD: Participants consisted of 237 Korean adolescent psychiatric patients whose scores on these measures were compared in terms of internal consistency and predictive validity. RESULTS: Scores on SUB exhibited superior internal consistency to that of the MMPI-A substance abuse scales. Further, scores on SUB predicted substance abuse more accurately than did the optimal combination of scores on the MMPI-A substance abuse scales. CONCLUSION: Results provide strong support for the use of the Korean MMPI-A-RF SUB scale when assessing substance abuse in Korean youth.

Functional principal component analysis for identifying multivariate patterns and archetypes of growth, and their association with long-term cognitive development.

For longitudinal studies with multivariate observations, we propose statistical methods to identify clusters of archetypal subjects by using techniques from functional data analysis and to relate longitudinal patterns to outcomes. We demonstrate how this approach can be applied to examine associations between multiple time-varying exposures and subsequent health outcomes, where the former are recorded sparsely and irregularly in time, with emphasis on the utility of multiple longitudinal observations in the framework of dimension reduction techniques. In applications to children's growth data, we investigate archetypes of infant growth patterns and identify subgroups that are related to cognitive development in childhood. Specifically, "Stunting" and "Faltering" time-dynamic patterns of head circumference, body length and weight in the first 12 months are associated with lower levels of long-term cognitive development in comparison to "Generally Large" and "Catch-up" growth. Our findings provide evidence for the statistical association between multivariate growth patterns in infancy and long-term cognitive development.

Comparison of the clinical outcome of frozen-thawed embryo transfer with and without pretreatment with a gonadotropin-releasing hormone agonist.

OBJECTIVE: To describe the clinical outcomes of frozen-thawed embryo transfer (FET) with artificial preparation of the endometrium, using a combination of estrogen (E2) and progesterone (P4) with or without a gonadotropin-releasing hormone agonist (GnRHa), and the modified natural cycle (MNC) with human chorionic gonadotropin (hCG) trigger. METHODS: In this retrospective study, we evaluated 187 patients during 3 years (February 2012-April 2015). The patients were allocated to the following treatment groups: group A, comprising 113 patients (181 cycles) who received GnRHa+E2+P4; group B, comprising 49 patients (88 cycles) who received E2+P4; and group C, comprising 25 patients (42 cycles) who received hCG+P4. The inclusion criteria were regular menstrual cycles (length 24-35 days) and age 21-45 years. RESULTS: The primary outcome of the study - implantation rate (IR) per embryo transferred - was not statistically different among the 3 groups. Similar results were found for the IRs with fetal heartbeat per embryo transferred (68/181 [37.6%] in group A vs. 22/88 [25.0%] in group B vs. 14/42 [33.3%] in group C) and for the live birth rates (LBRs) per embryo transferred (56/181 [30.9%] in group A vs. 18/88 [20.5%] in group B vs. 11/42 [26.2%] in group C). CONCLUSION: Although the pregnancy outcomes were better in the hormone therapy with GnRHa group, hormone therapy FET with GnRHa for pituitary suppression did not result in significantly improved IRs and LBRs when compared with hormone therapy FET without GnRHa or MNC FET.

Gender differences on the MMPI across American and Korean adult and adolescent normative samples.

The purpose of this study was to examine whether gender differences on the Minnesota Multiphasic Personality Inventory-2 (MMPI-2; Butcher, Dahlstrom, Graham, Tellegen, & Kaemmer, 1989) and Minnesota Multiphasic Personality Inventory-Adolescent (MMPI-A; Butcher et al., 1992) items are comparable across 2 distinctive cultural samples: Americans and Koreans. Using large, representative adult and adolescent samples from both cultures, we found that the American samples were associated with a higher proportion of items with gender differences than the Korean samples. The American adult sample produced gender differences on a higher proportion of items than did the American adolescent sample, but no such age difference was found between the Korean samples. Despite these differences between cultures and between age groups, content dimensions underlying items with gender differences were very similar across cultures and age groups, centering on stereotypical gender interests, behaviors, and emotions.

Unbalanced sample size effect on genome-wide population differentiation studies.

The fixation index (F(ST)) is one of the most widely used measurements of genetic distance between populations. The data set from the international HapMap project has been served as a reference data set for population differentiation studies. F(ST) is commonly used in order to compare the sample data with HapMap data. In this study, however, we show that the use of F(ST) without consideration of sample sizes may mislead the result. In particular, we first demonstrate that F(ST) suffers from imbalance of sample sizes through simulation studies and through the analysis of a large scale Korean genome-wide association data. Then, we propose a modified version of F(ST) which is shown to be more robust to imbalance of sample size. In addition, the chi-square test commonly used for homogeneity test is shown to perform similarly to the modified version of F(ST).