Jisuk Bae

Test-Retest Reliability of a Questionnaire for the Korea Youth Risk Behavior Web-Based Survey

OBJECTIVES A web-based survey has been administered annually since 2005 throughout Korea to assess the prevalence of adolescent health risk behaviors among middle and high school students. The aim of this study was to evaluate the test-retest reliability of the Korea Youth Risk Behavior Web-based Survey (KYRBWS) questionnaire. METHODS A convenience sample of 2298 middle and high school students participated in self-administered questionnaire surveys twice, approximately two weeks apart, in 2008. The percent agreement, kappa statistics, and prevalence rates at the first and second surveys were computed for the core subset of 39 self-reported health risk behavior indices of the KYRBWS. RESULTS Among 39 indices, seven indices had kappas ≥ 0.81 and all of the indices had kappas ≥ 0.41. Based on non-overlapping 95% confidence intervals, three indices had significantly different prevalence rates between the first and second surveys. In the subgroup analyses by school grade and gender, two indices had significantly different reliability estimates between middle and high school students. There were no significantly different reliability estimates between male and female students, except for one index. CONCLUSIONS This study demonstrated that the reliability estimates for the KYRBWS questionnaire are varied, but generally reliable over time. The indices with low reliability estimates need to be evaluated further in order to determine whether the indices should be modified or deleted from future versions of the KYRBWS.

Concentrations of perfluoroalkyl compounds in maternal and umbilical cord sera and birth outcomes in Korea

This study analyzed the concentrations of perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorohexane sulfonate (PFHxS) in maternal and umbilical cord sera at delivery from the general population in Korea. Seventy samples were analyzed with ion-pairing and LC/MS/MS. PFOS, PFOA and PFHxS were detected in both maternal and umbilical cord sera. There was a high correlation of PFC concentrations between maternal and cord serum samples, implying transplacental transport. Ranking of transplacental transfer efficiency was PFOA>PFHxS>PFOS. Students t-tests revealed that concentrations of maternal PFOA were related with decreases in birth weight, birth length and ponderal index, suggesting a possible impact on fetal growth. With multiple logistic regression models, maternal PFOS concentration showed a significant inverse association with ponderal index (OR=0.22; 95% CI, 0.05-0.90). Umbilical cord PFHxS concentration showed a significant inverse association with birth weight (OR=0.26; 95% CI, 0.08-0.85) or a marginally significant inverse association with birth length (OR=0.33; 95% CI, 0.09-1.17). This is the first report demonstrating an inverse association of birth outcomes with PFHxS exposure. Concentrations of maternal PFOA were decreased with parity, implying that delivery is one of the major routes for PFOA elimination in women. This study demonstrated prenatal exposure of PFCs through placental transfer which could result in possible developmental effects in the population sampled. Our results may provide data basis to conduct a larger scale investigation into developmental effects of PFCs in the future and contribute to understanding levels of PFC contaminations from a variety of populations in the globe.

Validity of Self-Reported Height, Weight, and Body Mass Index of the Korea Youth Risk Behavior Web-Based Survey Questionnaire

OBJECTIVES Self-reported anthropometric values, such as height and weight, are used to calculate body mass index (BMI) and assess the prevalence of obesity among adolescents. The aim of this study was to evaluate the validity of self-reported height, weight, and BMI of the Korea Youth Risk Behavior Web-based Survey questionnaire. METHODS A convenience sample of 137 middle school students and 242 high school students completed a self-administered questionnaire in 2008. Body height and weight were directly measured after self-reported values were obtained from the questionnaire survey. Sensitivity, specificity, and kappa statistics were computed in order to evaluate the validity of the prevalence of obesity (BMI ≥ 95th percentile or ≥ 25 kg/m(2)) based on self-reported data. RESULTS Self-reported weight and BMI tended to be underestimated. Self-reported height tended to be overestimated among middle school females and high school males. Obese adolescents tended to underestimate their weight and BMI and overestimate their height more than non-obese adolescents. The prevalence estimate of obesity based on self-reported data (10.6%) was lower than that based on directly measured data (15.3%). The estimated sensitivity of obesity based on self-reported data was 69.0% and the specificity was 100.0%. The value of kappa was 0.79 (95% confidence interval, 0.70-0.88). CONCLUSIONS This study demonstrated that self-reported height and weight may lead to the underestimation of BMI and consequently the prevalence of obesity. These biases should be taken into account when self-reported data are used for monitoring the prevalence and trends of obesity among adolescents nationwide.

Greater prevalence of seropositivity for anti-cyclic citrullinated peptide antibody in unaffected first-degree relatives in multicase rheumatoid arthritis-affected families

Background/Aims This study determined the prevalence and determinants of seropositivity for rheumatoid factor (RF), anti-cyclic citrullinated peptide (anti-CCP) antibody, and anti-mutated citrullinated vimentin (anti-MCV) antibody in unaffected first-degree relatives (FDRs) of rheumatoid arthritis (RA) patients. Methods A total of 337 subjects (135 with RA and 202 FDRs) were enrolled in this case-control study. Serum RF, anti-CCP antibody, and anti-MCV antibody were assayed. Subjects in multicase families (≥ 2 affected FDRs within the same family) were identified. Multivariate logistic regression analysis was used to identify risk factors associated with RA-related autoantibodies. Results Seropositivity for RF, anti-CCP antibody, or anti-MCV antibody was detected in 14.4%, 5.0%, or 13.4% of unaffected FDRs, respectively. Anti-CCP antibody seropositivity was more prevalent in FDRs in multicase families (17.8%) than in those not in multicase families (1.3%, p < 0.0001). Significant correlations between RA-associated autoantibodies were detected in the FDR group (between RF and anti-CCP antibody: r = 0.366, p < 0.0001; between RF and anti-MCV antibody: r = 0.343, p < 0.0001; and between anti-CCP antibody and anti-MCV antibody: r = 0.849, p < 0.0001). After adjustment for age and sex, anti-CCP antibody seropositivity in FDRs was significantly associated with being in a multicase family (odds ratio, 49.8; 95% confidence interval, 5.6 to 441.6). Conclusions The association between anti-CCP antibody seropositivity in unaffected FDRs and being in a multicase family suggests that genetic and/or environmental factors may increase the risk for RA development in unaffected FDRs.

Higher consumption of sugar-sweetened soft drinks increases the risk of hyperuricemia in Korean population: The Korean Multi-Rural Communities Cohort Study

OBJECTIVE The clinical implication of sugar-sweetened soft drinks on the risk of hyperuricemia has increased, especially in Western population studies. The aim of this study is to clarify the association between sugar-sweetened soft drinks and fruit drinks made from oranges and apples and the risk of hyperuricemia in the Korean Multi-Rural Communities Cohort. METHODS A total of 9400 subjects were enrolled in the Korean Multi-Rural Communities Cohort Study, and a cross-sectional analysis was performed. Five quintiles (Q1-Q5) according to consumption of soft drinks and other fruit/fruit juices were classified and then categorized into three groups (Q1-Q3, Q4, and Q5) to assess the risk of hyperuricemia. Information on dietary intake was collected by well-trained interviewers using validated food frequency questionnaires. RESULTS Higher consumption of sugar-sweetened soft drinks (Q5) increased the risk of hyperuricemia in males (adjusted OR = 1.35, 95% CI: 1.07-1.71) with a linear trend (p for trend = 0.01) and in females (adjusted OR = 1.40, 95% CI: 1.03-1.90) with no linear trend (p for trend = 0.09), compared to lower consumption (Q1-Q3). However, there were no significant differences of serum uric acid level according to the three categories of soft drink consumption, Q1-Q3, Q3, and Q5, in males (p = 0.21) or in females (p = 0.16), whereas all subjects showed statistical significance of serum uric acid level within the categories (p < 0.001). Estimated amount of soft drink intake was associated with serum uric acid level in males (β = 0.001; p = 0.01) but not in females (β = 0.0005; p = 0.10). CONCLUSION Higher consumption of sugar-sweetened soft drinks increased the risk of hyperuricemia in the Korean population, showing a differential linear trend for hyperuricemia according to gender.

Changes in the Distribution of Maternal Age and Parity and Increasing Trends in the Low Birth Weight Rate in Korea Between 1995 and 2005

Objectives This study measured the impact of shifts in maternal age and parity on the increase in the low birth weight (LBW) rate in Korea. Methods We obtained raw data for all 6 397 945 live births registered at the Korea National Statistical Office between 1995 and 2005. We calculated the proportion of increment in the LBW rate due to changes in the distribution of maternal age and parity (AP-dis) and the proportion due to changes in the age- and parity-specific LBW rate (AP-spe). Results The LBW rate increased from 3.02% in 1995 to 4.28% in 2005. The multiple birth rate increased from 1.32% to 2.19% during the same period. Of the 1.26% points increment in the LBW rate, 0.64% points occurred among singleton births and 0.62% points occurred among multiple births. Changes in the AP-dis accounted for 50% of the increase in the LBW rate among singleton births, but did not contribute to the increase in the LBW rate among multiple births. The remainder of the total increment in the LBW rate was explained by the increase in the AP-spe. Conclusions This study demonstrated that shifts in maternal age and parity among singleton births and increased multiple births were important contributors to the increment in the LBW rate. This study also revealed that the increase in the AP-spe was an equally important contributor as the shifts in maternal age and parity to the increment in the LBW rate among singleton births and was a major contributor among multiple births.

The effect of vitamin C intake on the risk of hyperuricemia and serum uric acid level in Korean Multi-Rural Communities Cohort

OBJECTIVE The aim of this study was to determine the association between vitamin C intake and risk of hyperuricemia or serum uric acid levels in male and female subjects in the Korean Multi-Rural Communities Prospective Cohort. METHODS This cross-sectional analysis was conducted in 9400 subjects enrolled in the Korean Multi-Rural Communities Cohort Study. The risk of hyperuricemia was assessed in five quintiles (Q1 to Q5) according to dietary and total vitamin C intake using multivariate-adjusted logistic regression models. Relationships between serum uric acid levels and vitamin C intake were evaluated using linear regression analysis after adjustment for covariates. Information about dietary components was collected using validated food frequency questionnaires. RESULTS Dietary vitamin C intake, but not total vitamin C intake, was significantly different between hyperuricemic and non-hyperuricemic subjects in males (P=0.01) and females (P=0.02). The risk of hyperuricemia decreased with increased dietary vitamin C intake in male and female subjects after multivariate adjustment (P for trend=0.002 in males and P for trend=0.02 in females). An effect of total vitamin C intake on hyperuricemia risk was identified in females (P for trend=0.04), but not males (P for trend=0.06). Serum uric acid level was linearly associated with total vitamin C intake in females (β=-0.0001, P=0.01), but not with dietary vitamin C intake in either gender. CONCLUSION This study showed that vitamin C intake might be in part responsible for hyperuricemia or serum uric acid level in the Korean Multi-Rural Communities Cohort.

Influence of asthma on the longitudinal trajectories of cigarette use behaviors from adolescence to adulthood using latent growth curve models.

Objectives: While epidemiologic research indicates that the prevalence of risk-taking behaviors including cigarette smoking among young people with asthma is substantial, the longitudinal patterns of cigarette smoking in this vulnerable population have received little attention. The aim of this study was to evaluate differences in the longitudinal trajectories of cigarette use behaviors from adolescence to adulthood between young people with and without asthma. Methods: Data from the National Longitudinal Study of Adolescent to Adult Health (Add Health) during the years 1994 to 1995 (Wave I, adolescence), 2001 to 2002 (Wave III, young adulthood), and 2007 to 2008 (Wave IV, adulthood) were analyzed (n=12 244). Latent growth curve models were used to examine the longitudinal trajectories of cigarette use behaviors during the transition to adulthood according to asthma status. Results: Regardless of asthma status, the trajectory means of cigarette use behaviors were found to increase, and then slightly decrease from adolescence to adulthood. In total participants, there were no statistically significant differences in initial levels and changes in cigarette use behaviors according to asthma status. However, in select sex and race subgroups (i.e., females and non-whites), former asthmatics showed greater escalation in cigarette use behaviors than did non-asthmatics or current asthmatics. Conclusions: This study indicated that the changing patterns of cigarette use behaviors during the transition to adulthood among young people with asthma are comparable to or even more drastic than those among young people without asthma.

Modifying Effect of Suicidal Ideation on the Relationship Between Asthma and Cigarette Use Behaviors Among Korean Adolescents

Objectives Although cigarette smoking is known to be related to the exacerbation of asthma symptoms, several studies have indicated that the prevalence of cigarette smoking among asthmatic adolescents is similar to or even higher than that among non-asthmatic adolescents. The aim of this study was to evaluate the relationship between asthma and cigarette use behaviors and whether or not the presence of suicidal ideation modifies this relationship among Korean adolescents. Methods We analyzed data from the 2008 Korea Youth Risk Behavior Web-based Survey, which included a nationally representative sample of middle and high school students. Multiple logistic regression models were used to calculate odd ratios and 95% confidence intervals of cigarette use behaviors among current asthmatics, former asthmatics, and non-asthmatics, after adjusting for gender, grade, school records, socioeconomic status, current alcohol use, and suicidal ideation. Results Of 75 238 study participants, 3.5% were current asthmatics and 4.5% were former asthmatics. Compared with non-asthmatics, asthmatics were more likely to report current cigarette use, frequent and heavy cigarette use, and cigarette use before 13 years of age. There were statistically significant interactions between asthma and suicidal ideation in cigarette use behaviors. Conclusions This study demonstrated that asthmatic adolescents are more likely than non-asthmatic adolescents to engage in cigarette use behaviors and the presence of suicidal ideation is an effect modifier of the relationship between asthma and cigarette use behaviors. Particular attention should be paid to the awareness of health risks of cigarette smoking and mental health problems among asthmatic adolescents.

Maternal and paternal serum concentrations of persistent organic pollutants and the secondary sex ratio: A population-based preconception cohort study

ABSTRACT Recent declines in the secondary sex ratio (SSR), defined as the ratio of males to females at birth, in some industrialized countries may be attributed to exposure to environmental toxicants such as persistent organic pollutants (POPs). This study aimed to evaluate the association of couples’ preconception exposure to POPs with the SSR. The study cohort comprised 235 couples who were enrolled in the Longitudinal Investigation of Fertility and the Environment (LIFE) Study between 2005 and 2009 prior to conception and prospectively followed through delivery of a singleton birth. Upon enrollment, couples’ serum concentrations (ng/g) were measured for 9 organochlorine pesticides, 1 polybrominated biphenyl, 10 polybrominated diphenyl ethers, and 36 polychlorinated biphenyls (PCBs). Birth outcome data including infant sex were collected upon delivery. Modified Poisson regression models were used to estimate the relative risks (RRs) and 95% confidence intervals (CIs) of a male birth for each chemical. Of the 56 POPs examined, maternal PCB 128 and paternal hexachlorobenzene were significantly associated with a female excess (RRs, 0.75 [95% CI, 0.60–0.94] and 0.81 [95% CI, 0.68–0.97] per 1 SD increase in log‐transformed serum chemical concentrations, respectively), whereas maternal mirex and paternal PCB 128 and p,p′‐dichlorodiphenyldichloroethylene were significantly associated with a male excess (RR range, 1.10–1.22 per 1 SD increase in log‐transformed serum chemical concentrations). After adjusting for multiple comparisons, only maternal mirex remained significantly associated with the SSR. This exploratory study on multiple classes of POPs demonstrated no conclusive evidence on the association between parental preconception exposure to POPs and the SSR. HIGHLIGHTSRecent declines in the SSR in some countries may be attributed to exposure to POPs.Maternal PCB 128 and paternal HCB were associated with a female excess.Maternal mirex and paternal PCB 128 and p,p′‐DDE were associated with a male excess.These findings await corroboration given the exploratory design of this study.