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1.  Longitudinal Consistency in Self-Reported Age of First Vaginal Intercourse Among Young Adults 
Journal of sex research  2012;51(1):97-106.
We examined consistency in self-reports of age at first vaginal sex among 9,399 male and female respondents who participated in Waves III and IV (separated by approximately 7 years) of the National Longitudinal Study of Adolescent Health (Add Health). Respondents were coded as consistent if they reported an age at first vaginal intercourse at Wave IV that was within 1 year of the age they reported at Wave III. Sociodemographic, behavioral, and cognitive predictors of consistency were examined using bivariate and multivariate logistic regression. Overall, 85.43% of respondents were able to provide consistent reports. Among both males and females, consistency was associated with age, years since first vaginal intercourse, race/ethnicity, and lifetime number of other-sex partners in final multivariate models. Respondents who were older and had more recently had their first sexual experience were more likely to be consistent. For females only, those who reported a history of non-parental, physically forced sex were less likely to be consistent. Most young adults consistently report age at first vaginal intercourse, supporting the credibility of retrospective self-reports about salient sexual events such as timing of first vaginal intercourse.
PMCID: PMC3955171  PMID: 23237101
Reliability and Validity of Measures; Quantitative/Statistical/Survey; Childhood, Adolescence, Adolescent Sexuality; Assumptions of sex research
2.  Risk Factors for Invasive Candidiasis in Infants >1500 g Birth Weight 
We describe the incidence, risk factors, and outcomes of invasive candidiasis in infants >1500 g birth weight.
We conducted a retrospective cohort study of infants >1500 g birth weight discharged from 305 NICUs in the Pediatrix Medical Group from 2001–2010. Using multivariable logistic regression, we identified risk factors for invasive candidiasis.
Invasive candidiasis occurred in 330/530,162 (0.06%) infants. These were documented from positive cultures from ≥1 of these sources: blood (n=323), cerebrospinal fluid (n=6), or urine from catheterization (n=19). Risk factors included day of life >7 (OR 25.2; 95% CI 14.6–43.3), vaginal birth (OR 1.6 [1.2–2.3]), exposure to broad-spectrum antibiotics (OR 1.6 [1.1–2.4]), central venous line (OR 1.8 [1.3–2.6]), and platelet count <50,000/mm3 (OR 3.7 [2.1–6.7]). All risk factors had poor sensitivities, low positive likelihood ratios, and low positive predictive values. The combination of broad-spectrum antibiotics and low platelet count had the highest positive likelihood ratio (46.2), but the sensitivity of this combination was only 4%. Infants with invasive candidiasis had increased mortality (OR 2.2 [1.3–3.6]).
Invasive candidiasis is uncommon in infants >1500 g birth weight. Infants at greatest risk are those exposed to broad-spectrum antibiotics and with platelet counts of <50,000/mm3.
PMCID: PMC3578110  PMID: 23042050
candidiasis; candidemia; neonates; neonatal intensive care unit
3.  The Association between Sequences of Sexual Initiation and the Likelihood of Teenage Pregnancy 
Few studies have examined the health and developmental consequences, including unintended pregnancy, of different sexual behavior initiation sequences. Some work suggests that engaging in oral-genital sex first may slow the transition to coital activity and lead to more consistent contraception among adolescents.
Using logistic regression analysis, we investigated the association between sequences of sexual initiation (i.e., initiating oral-genital or vaginal sex first based on reported ages of first experience) and the likelihood of subsequent teenage pregnancy among 6,069 females who reported vaginal sex before age 20 and participated in Waves I and IV of the National Longitudinal Study of Adolescent Health (Add Health).
Among females initiating vaginal sex first, 31.4% reported a teen pregnancy. Among females initiating two behaviors at the same age, 20.5% reported a teen pregnancy. Among females initiating oral-genital sex first, 7.9% reported a teen pregnancy. In multivariate models, initiating oral-genital sex first, with a delay of at least one year to vaginal sex, and initiating two behaviors within the same year were each associated with a lower likelihood of adolescent pregnancy, relative to teens who initiated vaginal sex first (OR=0.23, 95% CI (0.15, 0.37) and OR=0.78, 95% CI (0.60, 0.92), respectively).
How adolescents begin their sexual lives may be differentially related to positive and negative health outcomes. To develop effective pregnancy prevention efforts for teens and ensure programs are relevant to youths’ needs, it is important to consider multiple facets of sexual initiation and their implications for adolescent sexual health and fertility.
PMCID: PMC3551538  PMID: 23332489
4.  Associations Between Patterns of Emerging Sexual Behavior and Young Adult Reproductive Health 
Identifying young adult outcomes associated with adolescent sexual behavior, including patterns of first oral, vaginal and anal sex, is critical to promoting healthy sexual development.
Associations between patterns of emerging sexual behavior, defined using latent class analysis, and young adult sexual and reproductive health were examined among 9,441 respondents to Waves 1 (1994–1995), 3 (2001–2002) and 4 (2008) of the National Longitudinal Study of Adolescent Health. Logistic regression analyses examined associations between class membership and young adult outcomes, and tested for interactions by race and ethnicity.
Compared with respondents who initiated vaginal sex first and reported other sexual behaviors within two years, those who initiated oral and vaginal sex during the same year had similar odds of having had an STD diagnosis ever or in the last year, of having had concurrent sexual partnerships in the last year and of having exchanged sex for money. However, respondents who postponed sexual activity had reduced odds of each outcome (odds ratios, 0.2–0.4); those who initiated vaginal sex and reported only one type of sexual behavior had reduced odds of reporting STD diagnoses and concurrent partnerships (0.4–0.6). Respondents who reported early initiation of sexual activity combined with anal sex experience during adolescence had elevated odds of having had concurrent partnerships (1.6). The data suggest racial and ethnic disparities even when patterns of emerging sexual behavior were the same.
Patterns of early sexual behavior considered high-risk may not predict poor sexual and reproductive health in young adulthood.
PMCID: PMC3531866  PMID: 23231329
5.  Assessing variance components in multilevel linear models using approximate Bayes factors: A case study of ethnic disparities in birthweight 
Racial/ethnic disparities in birthweight are a large source of differential morbidity and mortality worldwide and have remained largely unexplained in epidemiologic models. We assess the impact of maternal ancestry and census tract residence on infant birth weights in New York City and the modifying effects of race and nativity by incorporating random effects in a multilevel linear model. Evaluating the significance of these predictors involves the test of whether the variances of the random effects are equal to zero. This is problematic because the null hypothesis lies on the boundary of the parameter space. We generalize an approach for assessing random effects in the two-level linear model to a broader class of multilevel linear models by scaling the random effects to the residual variance and introducing parameters that control the relative contribution of the random effects. After integrating over the random effects and variance components, the resulting integrals needed to calculate the Bayes factor can be efficiently approximated with Laplace’s method.
PMCID: PMC3784317  PMID: 24082430
Bayes factors; Laplace approximation; hierarchical; multilevel linear model; variance components
6.  Antimüllerian Hormone as a Predictor of Natural Fecundability in Women Aged 30–42 Years 
Obstetrics and gynecology  2011;117(4):10.1097/AOG.0b013e3182116bc8.
To generate estimates of the association between markers of ovarian aging and natural fertility in a community sample at risk for ovarian aging.
Women aged 30–44 years with no history of infertility who had been trying to conceive for less than 3 months provided early-follicular phase serum and urine (N=100). Subsequently, these women kept a diary to record menstrual bleeding and intercourse and conducted standardized pregnancy testing for up to 6 months. Serum was analyzed for estradiol, follicle-stimulating hormone (FSH), antimüllerian hormone, and inhibin B. Urine was analyzed for FSH and estrone 3-glucuronide (E13G). Diary data on menstrual cycle day and patterns of intercourse were used to calculate day-specific fecundability ratios.
Sixty-three percent of subjects conceived within 6 months. After adjusting for age, 18 women (18%) with serum antimüllerian hormone levels of 0.7 ng/ml or less had significantly reduced fecundability given intercourse on a fertile day compared to women with higher antimüllerian hormone levels (fecundability ratio 0.38, 95% CI:0.08–0.91). The day-specific fecundability for women with early-follicular phase serum FSH values greater than 10 mIU/ml compared to women with lower FSH levels was also reduced, though nonsignificantly (11% of women affected; fecundability ratio 0.44, 95% CI: 0.08, 1.10). The association with urinary FSH was weaker (27% women affected; fecundability ratio 0.61, 95% CI: 0.26, 1.26), and the associations for the other markers were weaker still.
Early-follicular phase antimüllerian hormone appears to be associated with natural fertility in the general population.
PMCID: PMC3825553  PMID: 21422850
7.  Pregravid body mass index, psychological factors during pregnancy, and breastfeeding duration: is there a link? 
Maternal & child nutrition  2011;8(4):423-433.
Breastfeeding rates in the U.S. are low and one possible reason may be the high prevalence of overweight/obesity among women of childbearing age. This analysis examined the association between pregravid body mass index (BMI) and breastfeeding duration and explored whether depressive symptoms, perceived stress and anxiety during pregnancy mediated this relationship. Participants (n = 550) in the Pregnancy, Infection, and Nutrition Postpartum Study were recruited through prenatal clinics prior to 20 weeks gestation and followed to 12 months postpartum. Duration of any breastfeeding was categorized as: none, less than 4 months, 4 to 6 months, 7 to 12 months, and more than 12 months (referent). Exclusive breastfeeding was categorized as less than 1 month, 1 to less than 4 months, and 4 months or more (referent). Being overweight/obese before pregnancy (35.7% of 550) was inversely associated with the durations of any and exclusive breastfeeding. Women who entered pregnancy overweight or obese were more likely to not initiate breastfeeding [RRR =5.39 (95% CI: 2.41, 12.04)] and to breastfeed less than four months [RRR = 2.38 (1.33, 4.27)] compared to women of normal weight status. Among women who initiated breastfeeding, being overweight or obese versus normal weight was related to exclusively breastfeeding less than 1 month [RRR = 2.09 (1.24, 3.51)]. We did not find evidence to support mediation by depressive symptoms, perceived stress or anxiety during pregnancy. Future research needs to explore the reasons behind the association between overweight/obesity and breastfeeding duration.
PMCID: PMC3329574  PMID: 21951308
Overweight; obesity; pregravid BMI; pregnancy; breastfeeding duration; depressive symptoms; stress; anxiety
8.  Pregravid body mass index is associated with early introduction of complementary foods 
To determine whether women who entered pregnancy overweight or obese were less likely to follow American Academy of Pediatrics (AAP) guidelines for introducing complementary foods to infants after four months of age. In addition, to explore whether psychological factors accounted for any of the effect of pregravid body mass index (BMI) on age of complementary food introduction.
A prospective cohort study from 2001 to 2005 which recruited pregnant women between 15 to 20 gestational weeks with follow-up through 12 months postpartum from University of North Carolina hospitals (n = 550).
Multinomial logit models estimated relative risk ratios (RRR). The outcome was age of complementary food introduction, categorized as less than four months of age, four to six, and six months or later (referent). Maternal BMI was categorized as underweight (< 18.5 kg/m2), normal-weight (18.5 kg/m2 to 24.9 kg/m2), and overweight/obese (≥ 25.0 kg/m2). A series of regression analyses tested mediation by psychological factors measured during pregnancy (depressive symptoms, stress and anxiety).
More than a third of the study population (35.7% of 550) entered pregnancy overweight/obese. The majority of participants (75.3%) introduced foods to their infants between four to six months of age. Compared with normal-weight women, those who were overweight/obese before pregnancy were more likely [RRR = 2.22 (1.23, 4.01)] to introduce complementary foods before the infant was four months old, adjusting for race, education, and poverty status. Depressive symptoms, stress and anxiety did not account for any of the effect of pregravid overweight/obesity on early food introduction.
The results suggest that overweight and obese women are more likely to introduce complementary foods early and that psychological factors during pregnancy do not influence this relationship. Future studies need to explore why overweight/obese women are less likely to meet the AAP recommendations for the introduction of complementary food.
PMCID: PMC3433719  PMID: 22939440
Overweight; obesity; pregravid body mass index; complementary food introduction
9.  Correlates of Physical Activity at Two Time Points During Pregnancy 
Correlates of prenatal physical activity can inform interventions, but are not well-understood.
Participants in the Pregnancy, Infection, and Nutrition 3 Study were recruited before 20 weeks gestation. Women self-reported frequency, duration, and mode of moderate and vigorous physical activities. We used logistic regression to identify correlates of any physical activity (≥10 minutes/week of any mode), any recreational activity (≥10 minutes/week), and high volume recreational activity (either ≥150 minutes/week of moderate or ≥75 minutes/week of vigorous). Our analysis included 1752 women at 19-weeks gestation and 1722 at 29 weeks.
Higher education, white race, and enjoyment of physical activity were positively correlated with all 3 outcomes. Any recreational activity was negatively associated with parity, body mass index, and history of miscarriage. The associations of history of miscarriage and body mass index differed at 19 weeks compared with 29 weeks. Single marital status, health professional physical activity advice, and time for activity were associated with high volume recreational activity only.
Correlates of physical activity differed by mode and volume of activity and by gestational age. This suggests that researchers planning physical activity interventions should consider the mode and amount of activity and the gestational age of the participants.
PMCID: PMC3749786  PMID: 22454434
leisure activity; gestational age; intervention; barriers; psychosocial
10.  Paternal occupation and birth defects: findings from the National Birth Defects Prevention Study 
Several epidemiologic studies have suggested that certain paternal occupations may be associated with an increased prevalence of birth defects in offspring. Using data from the National Birth Defects Prevention Study, we investigated the association between paternal occupation and birth defects in a case-control study of cases comprising over 60 different types of birth defects (n = 9998) and non-malformed controls (n = 4066) with dates of delivery between 1997 and 2004.
Using paternal occupational histories reported by mothers via telephone interview, jobs were systematically classified into 63 groups based on shared exposure profiles within occupation and industry. Data were analyzed using Bayesian logistic regression with a hierarchical prior for dependent shrinkage to stabilize estimation with sparse data.
Several occupations were associated with an increased prevalence of various birth defect categories, including: mathematical, physical and computer scientists; artists; photographers and photo processors; food service workers; landscapers and groundskeepers; hairdressers and cosmetologists; office and administrative support workers; sawmill workers; petroleum and gas workers; chemical workers; printers; material moving equipment operators; and motor vehicle operators.
Findings from this study might be used to identify specific occupations worthy of further investigation, and to generate hypotheses about chemical or physical exposures common to such occupations.
PMCID: PMC3744212  PMID: 22782864
Bayes theorem; congenital abnormalities; occupational exposure; occupations; paternal exposure
11.  Neighbourhood food environment and gestational diabetes in New York City 
The association between neighbourhood characteristics and gestational diabetes has not been examined previously. We investigated the relationship between the number of healthy food outlets (supermarkets; fruit/vegetable and natural food stores), and unhealthy food outlets (fast food; pizza; bodegas; bakeries; convenience, candy/nut and meat stores) in census tract of residence, and gestational diabetes in New York City. Gestational diabetes, census tract and individual-level covariates were ascertained from linked birth-hospital data for 210 926 singleton births from 2001 to 2002 and linked to commercial data on retail food outlets. Adjusted odds ratios (aOR) were estimated using a multilevel logistic model.
No association between food environment measures and gestational diabetes was found, with aORs ranging from 0.95 to 1.04. However, an increased odds of pre-pregnancy weight >200 lbs for women living in a given neighbourhood with no healthy food outlets [aOR = 1.14, 95% CI 1.07, 1.21] or only one healthy food place [aOR = 1.10, 95% CI 1.04, 1.18] relative to two or more healthy food outlets was found. Due to probable misclassification of neighbourhood food environment and pre-pregnancy obesity results are likely to be biased towards the null. Future research, including validity studies, on the neighbourhood food environment, obesity during pregnancy and gestational diabetes is warranted.
PMCID: PMC3734793  PMID: 20415754
gestational diabetes; maternal obesity; healthy food outlets
12.  A Bayesian Latent Variable Mixture Model for Longitudinal Fetal Growth 
Biometrics  2009;65(4):1233-1242.
Fetal growth restriction is a leading cause of perinatal morbidity and mortality that could be reduced if high risk infants are identified early in pregnancy. We propose a Bayesian model for aggregating 18 longitudinal ultrasound measurements of fetal size and blood flow into three underlying, continuous latent factors. Our procedure is more flexible than typical latent variable methods in that we relax the normality assumptions by allowing the latent factors to follow finite mixture distributions. Using mixture distributions also permits us to cluster individuals with similar observed characteristics and identify latent classes of subjects who are more likely to be growth or blood flow restricted during pregnancy. We also use our latent variable mixture distribution model to identify a clinically-meaningful latent class of subjects with low birth weight and early gestational age. We then examine the association of latent classes of intrauterine growth restriction with latent classes of birth outcomes as well as observed maternal covariates including fetal gender and maternal race, parity, body mass index (BMI), and height. Our methods identified a latent class of subjects who have increased blood flow restriction and below average intrauterine size during pregnancy who were more likely to be growth restricted at birth than a class of individuals with typical size and blood flow.
PMCID: PMC3717393  PMID: 19432784
Bayesian methods; birth weight; correlated data; intrauterine growth restriction; pre-term birth; latent variables; small for gestational age
13.  A prospective study of the association between vigorous physical activity during pregnancy and length of gestation and birthweight 
Maternal and Child Health Journal  2012;16(5):1031-1044.
Current U.S. pregnancy-related physical activity recommendations do not provide specific guidance for vigorous intensity activity. Our objective was to examine the associations between vigorous physical activity during pregnancy and length of gestation and birthweight. Women were recruited before 10 weeks gestation. At 13-16 weeks gestation, participants reported the type, frequency, and duration of their typical weekly vigorous physical activities. Activity domains included recreational, occupational, household, and child/adult care. Infant birth date was obtained from medical or vital records; if unavailable, self-report was used. Birthweight (from vital records) was studied among term births. We analyzed gestational age among 1,647 births using discrete-time survival analysis. We used logistic and linear regression to analyze preterm birth (birth at <37 weeks) and birthweight, respectively. Vigorous recreational activity was associated with longer gestation (any vs. none, hazard ratio (HR) [95% CI]: 0.85 [0.70, 1.05]) and we did not detect any dose-response association. Higher frequency of vigorous recreational activity sessions (adjusted for total volume of activity) was associated with a decreased odds of preterm birth (≥ 4 sessions/week vs. 0 or 1, OR [95% CI]: 0.08 (0.006, 1.0). Birthweight was not associated with physical activity measures. In summary, vigorous physical activity does not appear to be detrimental to the timing of birth or birthweight. Our data support a reduced risk of preterm birth with vigorous recreational activity, particularly with increased frequency of recreational activity sessions. Future studies should investigate the components of physical activity (i.e. intensity, duration, and frequency) in relation to birth outcomes.
PMCID: PMC3386423  PMID: 21674218
14.  Effect of Vaginal Lubricants on Natural Fertility 
Obstetrics and gynecology  2012;120(1):44-51.
Over-the-counter vaginal lubricants have been shown to negatively affect in vitro sperm motility. The objective of this study was to estimate the effect of vaginal lubricant use during procreative intercourse on natural fertility.
Women aged 30–44 years with no history of infertility who had been trying to conceive for less than 3 months completed a baseline questionnaire on vaginal lubricant use. Subsequently, women kept a diary to record menstrual bleeding, intercourse, and vaginal lubricant use and conducted standardized pregnancy testing for up to 6 months. Diary data were used to determine the fertile window and delineate lubricant use during the fertile window. A proportional hazards model was used to estimate fecundability ratios with any lubricant use in the fertile window considered as a time-varying exposure.
Of the 296 participants, 75 (25%) stated in their baseline questionnaire that they use vaginal lubricants while attempting to conceive. Based on daily diary data, 57% of women never used a lubricant, 29% occasionally used a lubricant, and 14% used a lubricant frequently. Women who used lubricants during the fertile window had similar fecundability to those women who did not use lubricants (fecundability ratio 1.05, 95% CI: 0.59, 1.85) after adjusting for age, partner race, and intercourse frequency in the fertile window.
Lubricants are commonly used by couples during procreative intercourse. Lubricant use during procreative intercourse does not appear to reduce the probability of conceiving.
PMCID: PMC3427535  PMID: 22914390
15.  Detecting Disease Outbreaks Using Local Spatiotemporal Methods 
Biometrics  2011;67(4):1508-1517.
A real-time surveillance method is developed with emphasis on rapid and accurate detection of emerging outbreaks. We develop a model with relatively weak assumptions regarding the latent processes generating the observed data, ensuring a robust prediction of the spatiotemporal incidence surface. Estimation occurs via a local linear fitting combined with day-of-week effects, where spatial smoothing is handled by a novel distance metric that adjusts for population density. Detection of emerging outbreaks is carried out via residual analysis. Both daily residuals and AR model-based de-trended residuals are used for detecting abnormalities in the data given that either a large daily residual or an increasing temporal trend in the residuals signals a potential outbreak, with the threshold for statistical significance determined using a resampling approach.
PMCID: PMC3698245  PMID: 21418049
Disease surveillance; Local linear estimation; Residual analysis; Lattice Data; Time series modeling
16.  The Effect of Water Disinfection By-products on Pregnancy Outcomes in Two Southeastern U.S. Communities 
To determine if exposure to DBPs during gestation increases the risk of adverse birth outcomes, specifically term small for gestational age (SGA) birth, preterm birth (PTB), and very PTB (<32 weeks gestation).
We used weekly measurements total trihalomethanes (TTHMs), 5 haloacetic acids (HAA5), and total organic halides (TOX) collected from two distribution systems to evaluate the associations between DBP concentrations and term SGA, PTB and very PTB using logistic regression.
We found no associations between DBPs and term-SGA. In the site with higher concentrations of bromine-containing DBPs, we found an association between TOX and PTB; this association was larger, though less precise, for very PTB.
Our results do not support an association between TTHMs or HAA5 and the birth outcomes investigated, but an association was found between increased TOX and PTB.
PMCID: PMC3693937  PMID: 21915074
17.  Effect of Body Image on Pregnancy Weight Gain 
Maternal and child health journal  2011;15(3):324-332.
The majority of women gain more weight during pregnancy than what is recommended. Since gestational weight gain is related to short and long-term maternal health outcomes, it is important to identify women at greater risk of not adhering to guidelines. The objective of this study was to examine the relationship between body image and gestational weight gain. The Body Image Assessment for Obesity tool was used to measure ideal and current body sizes in 1,192 women participating in the Pregnancy, Infection and Nutrition Study. Descriptive and multivariable techniques were used to assess the effects of ideal body size and discrepancy score (current—ideal body sizes), which reflected the level of body dissatisfaction, on gestational weight gain. Women who preferred to be thinner had increased risk of excessive gain if they started the pregnancy at a BMI ≤26 kg/m2 but a decreased risk if they were overweight or obese. Comparing those who preferred thin body silhouettes to those who preferred average size silhouettes, low income women had increased risk of inadequate weight gain [RR = 1.76 (1.08, 2.88)] while those with lower education were at risk of excessive gain [RR = 1.11 (1.00, 1.22)]. Our results revealed that body image was associated with gestational weight gain but the relationship is complex. Identifying factors that affect whether certain women are at greater risk of gaining outside of guidelines may improve our ability to decrease pregnancy-related health problems.
PMCID: PMC3665282  PMID: 20204481
Body image; Body dissatisfaction; Gestational weight gain; Pregnancy
18.  Beyond age at first sex: Patterns of emerging sexual behavior in adolescence and young adulthood 
The Journal of Adolescent Health  2011;50(5):456-463.
Although the emergence of sexual expression during adolescence and early adulthood is nearly universal, little is known about patterns of initiation.
We used latent class analysis to group 12,194 respondents from Waves I and IV of the National Longitudinal Study of Adolescent Health (Add Health) into one of five classes based on variety, timing, spacing, and sequencing of oral-genital, anal, and vaginal sex. Multinomial logistic regression models, stratified by biological sex, examined associations between sociodemographic characteristics and class membership.
Approximately half of respondents followed a pattern characterized predominately by initiation of vaginal sex first, average age of initiation of approximately 16 years, and spacing of one year or more between initiation of the first and second behaviors; almost one third initiated sexual activity slightly later but reported first experiences of oral-genital and vaginal sex within the same year. Classes characterized by postponement of sexual activity, initiation of only one type of behavior, or adolescent initiation of anal sex were substantially less common. Compared to White respondents, Black respondents were more likely to appear in classes characterized by initiation of vaginal sex first. Respondents from lower socioeconomic backgrounds were more likely to be in classes distinguished by early/atypical patterns of initiation.
A small number of typical and atypical patterns capture the emergence of sexual behavior during adolescence, but these patterns reveal complex associations among different elements of emerging sexuality that should be considered in future research.
PMCID: PMC3336094  PMID: 22525108
Oral sex; anal sex; latent class analysis; nationally representative; noncoital; sexuality development; adolescent sexual behavior; sociodemographic differences
19.  Cardiovascular Outcomes and the Physical and Chemical Properties of Metal Ions Found in Particulate Matter Air Pollution: A QICAR Study 
Environmental Health Perspectives  2013;121(5):558-564.
Background: This paper presents an application of quantitative ion character–activity relationships (QICAR) to estimate associations of human cardiovascular (CV) diseases (CVDs) with a set of metal ion properties commonly observed in ambient air pollutants. QICAR has previously been used to predict ecotoxicity of inorganic metal ions based on ion properties.
Objectives: The objective of this work was to examine potential associations of biological end points with a set of physical and chemical properties describing inorganic metal ions present in exposures using QICAR.
Methods: Chemical and physical properties of 17 metal ions were obtained from peer-reviewed publications. Associations of cardiac arrhythmia, myocardial ischemia, myocardial infarction, stroke, and thrombosis with exposures to metal ions (measured as inference scores) were obtained from the Comparative Toxicogenomics Database (CTD). Robust regressions were applied to estimate the associations of CVDs with ion properties.
Results: CVD was statistically significantly associated (Bonferroni-adjusted significance level of 0.003) with many ion properties reflecting ion size, solubility, oxidation potential, and abilities to form covalent and ionic bonds. The properties are relevant for reactive oxygen species (ROS) generation, which has been identified as a possible mechanism leading to CVDs.
Conclusion: QICAR has the potential to complement existing epidemiologic methods for estimating associations between CVDs and air pollutant exposures by providing clues about the underlying mechanisms that may explain these associations.
PMCID: PMC3673192  PMID: 23462649
air pollution; cardiovascular disease; multipollutant; QICAR; QSAR
20.  Breastfeeding and long-chain polyunsaturated fatty acid intake in the first 4 post-natal months and infant cognitive development: an observational study 
Maternal & child nutrition  2011;8(4):471-482.
The aim of this study was to examine infant feeding and the long-chain polyunsaturated fatty acid (LCPUFA) concentration of breast milk and formulas in relation to infant development. The prospective Pregnancy, Infection and Nutrition Study (n = 358) collected data on breastfeeding, breast milk samples and the formulas fed through 4 months post-partum. At 12 months of age, infants’ development was assessed (Mullen Scales of Early Learning). Linear regression was used to examine development in relation to breastfeeding, breast milk docosahexaenoic acid (DHA) and arachidonic acid (AA) concentration, and DHA and AA concentration from the combination of breast milk and formula. The median breast milk DHA concentration was 0.20% of total fatty acids [interquartile range (IQR) = 0.14, 0.34]; median AA concentration was 0.52% (IQR = 0.44, 0.63). Upon adjustment for preterm birth, sex, smoking, race and ethnicity and education, breastfeeding exclusivity was unrelated to development. Among infants exclusively breastfed, breast milk LCPUFA concentration was not associated with development (Mullen composite, DHA: adjusted β = −1.3, 95% confidence interval: −10.3, 7.7). Variables combining DHA and AA concentrations from breast milk and formula, weighted by their contribution to diet, were unassociated with development. We found no evidence of enhanced infant development related to the LCPUFA content of breast milk or formula consumed during the first four post-natal months.
PMCID: PMC3617566  PMID: 21615865
arachidonic acid; breast milk; docosahexaenoic acid; infant feeding; polyunsaturated fatty acids; breastfeeding
21.  Gestational weight gain and predicted changes in offspring anthropometrics between early infancy and 3 years 
Pediatric Obesity  2012;7(2):134-142.
To determine how gestational weight gain (GWG), categorized using the 2009 Institute of Medicine recommendations, relates to changes in offspring weight-for-age (WAZ), length-for-age (LAZ), and weight-for-length z-scores (WLZ) between early infancy and 3 years.
Women with singleton infants were recruited from the third cohort of the Pregnancy, Infection, and Nutrition Study (2001-2005). Term infants with at least one weight or length measurement during the study period were included (n=476). Multivariable linear mixed effects regression models estimated longitudinal changes in WAZ, LAZ, and WLZ associated with GWG.
In early infancy, compared to infants of women with adequate weight gain, those of women with excessive weight gains had higher WAZ, LAZ, and WLZ. Excessive GWG≥200% of the recommended amount was associated with faster rates of change in WAZ and LAZ and noticeably higher predicted mean WAZ and WLZ that persisted across the study period.
GWG represents a modifiable behavioral factor that is associated with offspring anthropometric outcomes. More longitudinal studies that utilize maternal and pediatric body composition measures are necessary to understand the nature of this association.
PMCID: PMC3313077  PMID: 22434753
gestational weight gain; obesity; longitudinal; anthropometrics; offspring
22.  Depressive Symptoms during Pregnancy and the Concentration of Fatty Acids in Breast Milk 
The aim of the present study was to examine the association between depressive symptoms in pregnancy and the concentration of long-chain polyunsaturated fatty acids (LCPUFAs) in breast milk. Women (n =287) enrolled in the Pregnancy, Infection, and Nutrition Study completed the Center for Epidemiologic Studies Depression Scale in pregnancy (<20 and 24–29 weeks) and had LCPUFAs measured in breast milk (4 months postpartum). Multiple linear regression was used to examine associations between depressive symptoms and breast milk LCPUFAs. Increasing depressive symptoms at <20 weeks were associated with lower docosahexaenoic acid concentrations (adjusted β=−1.15, 95% confidence interval =−2.12, −0.19). No similar associations were observed with other fatty acids nor between symptoms at 24–29 weeks and LCPUFAs. Depressive symptoms, even in the subclinical range, early in pregnancy are inversely associated with breast milk docosahexaenoic acid. This may have implications for the timing of screening and interventions for perinatal depression and the nutritional value of breast milk.
PMCID: PMC3609547  PMID: 22223516
depression; postpartum depression; fatty acids; pregnancy; breast milk; introduction
23.  Gestational Weight Gain and Birth Outcome in Relation to Prepregnancy Body Mass Index and Ethnicity 
Annals of epidemiology  2010;21(2):78-85.
The obesity epidemic raises concerns about the impact of excessive and insufficient weight gain during pregnancy.
We examined the association between gestational weight gain (GWG) and preterm birth, term small- and large-for-gestational-age (SGA and LGA), term birthweight, and term primary Cesarean delivery, considering prepregnancy body mass index (BMI) and ethnicity in a cohort of 33,872 New York City residents who gave birth between 1995 and 2003 and delivered in hospitals elsewhere in New York State.
Preterm birth (<37 weeks’ gestation) showed a modest U-shaped relationship, with projected GWG of <10 kg and 20+ kg associated with odds ratios of 1.4 and 1.3, respectively, relative to 10 to 14 kg. The pattern was stronger for preterm birth <32 weeks’ and for underweight women with low GWG and overweight/obese women with high GWG. Term SGA decreased and term LGA and birthweight increased monotonically with increasing GWG. Primary Cesarean delivery followed the same pattern as LGA, but less strongly.
Although the study is limited by potential selection bias and measurement error, our findings support the contention that GWG may be a modifiable predictor of pregnancy outcome that warrants further investigation, particularly randomized trials, to assess whether the relation is causal.
PMCID: PMC3586213  PMID: 20702110
Birth Weight; Cesarean Delivery; Fetal Growth Retardation; Fetal Macrosomia; Infant; Small-for-Gestational Age; Premature Birth; Weight Gain
24.  Self-Report Versus Ultrasound Measurement of Uterine Fibroid Status 
Journal of Women's Health  2012;21(3):285-293.
Much of the epidemiologic research on risk factors for fibroids, the leading indication for hysterectomy, relies on self-reported outcome. Self-report is subject to misclassification because many women with fibroids are undiagnosed. The purpose of this analysis was to quantify the extent of misclassification and identify associated factors.
Self-reported fibroid status was compared to ultrasound screening from 2046 women in Right From The Start (RFTS) and 869 women in the Uterine Fibroid Study (UFS). Log-binomial regression was used to estimate sensitivity (Se) and specificity (Sp) and examine differences by ethnicity, age, education, body mass index, parity, and miscarriage history.
Overall sensitivity was ≤0.50. Sensitivity was higher in blacks than whites (RFTS: 0.34 vs. 0.23; UFS: 0.58 vs. 0.32) and increased with age. Parous women had higher sensitivity than nulliparae, especially in RFTS whites (Se ratio=2.90; 95% confidence interval [CI]: 1.51, 5.60). Specificity was 0.98 in RFTS and 0.86 in UFS. Modest ethnic differences were seen in UFS (Sp ratio, black vs. white=0.90; 95% CI: 0.81, 0.99). Parity was inversely associated with specificity, especially among UFS black women (Sp ratio=0.84; 95% CI: 0.73, 0.97). Among women who reported a previous diagnosis, a shorter time interval between diagnosis and ultrasound was associated with increased agreement between the two measures.
Misclassification of fibroid status can differ by factors of etiologic interest. These findings are useful for assessing (and correcting) bias in studies using self-reported clinical diagnosis as the outcome measure.
PMCID: PMC3298676  PMID: 22044079
25.  Consumer product exposures associated with urinary phthalate levels in pregnant women 
Human phthalate exposure is ubiquitous, but little is known regarding predictors of urinary phthalate levels. To explore this, 50 pregnant women aged 18–38 years completed two questionnaires on potential phthalate exposures and provided a first morning void. Urine samples were analyzed for 12 phthalate metabolites. Associations with questionnaire items were evaluated via Wilcoxon tests and t-tests, and r-squared values were calculated in multiple linear regression models. Few measured factors were statistically significantly associated with phthalate levels. Individuals who used nail polish had higher levels of mono-butyl phthalate (p=0.048) than non-users. Mono-benzyl phthalate levels were higher among women who used eye makeup (p=0.034) or used makeup on a regular basis (p=0.004). Women who used cologne or perfume had higher levels of di-(2-ethylhexyl) phthalate metabolites. Household products, home flooring or paneling, and other personal care products were also associated with urinary phthalates. The proportion of variance in metabolite concentrations explained by questionnaire items ranged between 0.31 for mono-ethyl phthalate and 0.42 for mono-n-methyl phthalate. Although personal care product use may be an important predictor of urinary phthalate levels, most of the variability in phthalate exposure was not captured by our relatively comprehensive set of questionnaire items.
PMCID: PMC3439834  PMID: 22760436
Phthalates; pregnancy; biomonitoring; urine; personal care products

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