Nonparametric Bayes modeling with sample survey weights.

In population studies, it is standard to sample data via designs in which the population is divided into strata, with the different strata assigned different probabilities of inclusion. Although there have been some proposals for including sample survey weights into Bayesian analyses, existing methods require complex models or ignore the stratified design underlying the survey weights. We propose a simple approach based on modeling the distribution of the selected sample as a mixture, with the mixture weights appropriately adjusted, while accounting for uncertainty in the adjustment. We focus for simplicity on Dirichlet process mixtures but the proposed approach can be applied more broadly. We sketch a simple Markov chain Monte Carlo algorithm for computation, and assess the approach via simulations and an application.

Continuity of adolescent and early adult partner violence victimisation: association with witnessing violent crime in adolescence.

BACKGROUND: Although exposure to peer and family violence is a documented risk factor for adolescent dating violence, less is known about the relationship between violent crime exposure and dating violence victimisation. METHODS: Participants in the National Longitudinal Study of Adolescent Health (n = 4794) aged 13-17 years self-reported witnessing violent crime (someone being shot or stabbed) in the 12 months prior to Wave I interview (1994-95), physical partner violence victimisation within the 18 months prior to Wave II interview (1995-96), and physical and sexual partner violence victimisation within the 18 months prior to Wave III interview (2001). RESULTS: Twelve per cent of respondents reported dating violence victimisation at Wave II. Witnessing violent crime was positively associated with victimisation in crude (OR = 2.11, 95% CI 1.56 to 2.86) and adjusted (AOR = 1.53, 95% CI 1.09 to 2.15) analyses. Of the adolescent partner violence victims (n = 549), 32% reported continued victimisation into early adulthood; after adjusting for gender, age, urbanicity and childhood maltreatment history, witnessing violent crime in adolescence was negatively associated with having non-violent relationships in early adulthood (AOR = 0.40, 95% CI 0.19 to 0.84). In cross-sectional and longitudinal analyses, associations between violent crime exposure and victimisation did not vary by age, gender or race/ethnicity. CONCLUSION: Adolescents exposed to violent crime experience an increased risk of partner violence victimisation in adolescence and continuing victimisation into adulthood. Targeting dating violence prevention and intervention programmes to geographic areas with high levels of violent crime may be an efficient strategy to reach higher risk adolescents. Reducing community violent crime may also have spillover effects on partner violence.

Correlates of condom use among sexually experienced secondary-school male students in Nairobi, Kenya.

This study aimed to examine perceptual factors associated with condom use, and the relationship between condom use and the timing of sexual debut among male secondary school students in Nairobi, Kenya. Data are from the TeenWeb study, a school-based project that used the World Wide Web to assess the health needs of secondary school students, and tested the web's utility as a teaching and research modality. Analyses are based on 214 sexually experienced males aged 14 - 20 years who completed web-based questionnaires about their sexual attitudes and behaviour. Results indicate that students did not see themselves as susceptible to HIV/AIDS and believed condom effectiveness in preventing HIV to be low. Consequently, only a marginal association was found between agreeing that buying condoms is embarrassing and condom use at first sexual intercourse. However, contrary to expectation, agreeing that condoms often break (almost half of participants) was associated with a higher likelihood of condom use at first sex. Each year of delay in sexual debut increased the likelihood of using a condom at first sex by 1.44 times. In turn, having used a condom at first sex increased the likelihood of using one at the most recent sex by 4.81 times, and elevated general condom use ('most or all the time') by 8.76 times. Interventions to increase awareness about the role of condoms in preventing HIV, delay sexual initiation, and teach proper condom use among secondary-school students in Nairobi are needed.

Correlates of Condom use among Sexually Experienced Secondary School Male Students in Nairobi; Kenya

This study aimed to examine perceptual factors associated with condom use; and the relationship between condom use and the timing of sexual debut among male secondary school students in Nairobi; Kenya. Data are from the TeenWeb study; a school-based project that used the World Wide Web to assess the health needs of secondary school students; and tested the web's utility as a teaching and research modality. Analyses are based on 214 sexually experienced males aged 14 - 20 years who completed web-based questionnaires about their sexual attitudes and behaviour. Results indicate that students did not see themselves as susceptible to HIV/AIDS and believed condom effectiveness in preventing HIV to be low. Consequently; only a marginal association was found between agreeing that buying condoms is embarrassing and condom use at first sexual intercourse. However; contrary to expectation; agreeing that condoms often break (almost half of participants) was associated with a higher likelihood of condom use at first sex. Each year of delay in sexual debut increased the likelihood of using a condom at first sex by 1.44 times. In turn; having used a condom at first sex increased the likelihood of using one at the most recent sex by 4.81 times; and elevated general condom use (`most or all the time') by 8.76 times. Interventions to increase awareness about the role of condoms in preventing HIV; delay sexual initiation; and teach proper condom use among secondary-school students in Nairobi are needed

Parenting quality, DRD4, and the prediction of externalizing and internalizing behaviors in early childhood.

Recent research has found that the dopamine D4 receptor (DRD4) gene and maternal insensitivity may interact to predict externalizing behavior in preschoolers. The current study attempted to replicate and extend this finding in a sample of 18-30-month-old children. The current study examined two distinct dimensions of parenting (warm-responsive and negative-intrusive) as predictors of childhood externalizing and internalizing behavior. Further, race was investigated as a moderator of gene-environment relationships. Results revealed that high warm-responsive parenting was associated with decreased externalizing behavior only for African American children possessing the short polymorphism of DRD4. The data indicate that children may be differentially susceptible to different aspects of parenting depending on their genotype, and it is important to consider differences in racial composition when studying these relationships.

Gender differences in associations between depressive symptoms and patterns of substance use and risky sexual behavior among a nationally representative sample of U.S. adolescents.

OBJECTIVE: This study uses a cluster analysis of adolescents, based on their substance use and sexual risk behaviors, to 1) examine associations between risk behavior patterns and depressive symptoms, stratified by gender, and 2) examine gender differences in risk for depression. METHODS: Data are from a nationally representative survey of over 20,000 U.S. adolescents. Logistic regression was used to examine the associations between 16 risk behavior patterns and current depressive symptoms by gender. RESULTS: Compared to abstention, involvement in common adolescent risk behaviors (drinking, smoking, and sexual intercourse) was associated with increased odds of depressive symptoms in both sexes. However, sex differences in depressive symptoms vary by risk behavior pattern. There were no differences in odds for depressive symptoms between abstaining male and female adolescents (OR = 1.07, 95% CI 0.70-1.62). There were also few sex differences in odds of depressive symptoms within the highest-risk behavior profiles. Among adolescents showing light and moderate risk behavior patterns, females experienced significantly more depressive symptoms than males. CONCLUSIONS: Adolescents who engage in risk behaviors are at increased risk for depressive symptoms. Girls engaging in low and moderate substance use and sexual activity experience more depressive symptoms than boys with similar behavior. Screening for depression is indicated for female adolescents engaging in even experimental risk behaviors.

Partner violence among adolescents in opposite-sex romantic relationships: findings from the National Longitudinal Study of Adolescent Health.

OBJECTIVES: This report examines (1) the prevalence of psychological and minor physical violence victimization in a nationally representative sample of adolescents and (2) associations between sociodemographic factors and victimization. METHODS: Analyses are based on 7500 adolescents who reported exclusively heterosexual romantic relationships in the National Longitudinal Study of Adolescent Health. Items from the Conflict Tactics Scale were used to measure victimization. Associations between victimization patterns and sociodemographic characteristics were assessed with polytomous logistic regression. RESULTS: One third of adolescents reported some type of victimization, and 12% reported physical violence victimization. Although most sociodemographic characteristics were significantly associated with victimization, patterns varied by sex and type of victimization. CONCLUSIONS: Psychological and minor physical violence victimization is common in opposite-sex romantic relationships during adolescence. The sex-specific associations between sociodemographic characteristics and patterns of partner violence victimization underscore the importance of pursuing longitudinal, theory-driven investigations of the characteristics and developmental histories of both partners in a couple to advance understanding of this public health problem.

Smart teens don't have sex (or kiss much either).

PURPOSE: To examine the relationship between an intelligence measure and a wide spectrum of partnered sexual activity ranging from holding hands to sexual intercourse among adolescents. METHOD: Analyses are based on two separate samples of adolescents. The core sample of the National Longitudinal Study of Adolescent Health (Add Health) includes approximately 12,000 adolescents enrolled in the 7th to 12th grades. The Biosocial Factors in Adolescent Development projects followed approximately 100 white males and 200 black and white females over 3- and 2-year periods, respectively. Both studies used the Peabody Picture Vocabulary Test (PPVT) as an intelligence measure, and confidential self-reports of sexual activity. Logistic regression models were used to examine the relationship between PPVT scores and coital status in Add Health data; proportional hazard models were used to examine the timing of initiation of noncoital and coital activities as a function of PPVT scores in the Biosocial Factors sample. RESULTS: Controlling for age, physical maturity, and mother's education, a significant curvilinear relationship between intelligence and coital status was demonstrated; adolescents at the upper and lower ends of the intelligence distribution were less likely to have sex. Higher intelligence was also associated with postponement of the initiation of the full range of partnered sexual activities. An expanded model incorporating a variety of control and mediator variables was tested to identify mechanisms by which the relationship operates. CONCLUSIONS: Higher intelligence operates as a protective factor against early sexual activity during adolescence, and lower intelligence, to a point, is a risk factor. More systematic investigation of the implications of individual differences in cognitive abilities for sexual activities and of the processes that underlie those activities is warranted.

Effects of body fat on weight concerns, dating, and sexual activity: a longitudinal analysis of black and white adolescent girls.

Using data from a 2-year longitudinal study of 200 Black and White adolescent girls (mean age was 13.8 years at study entry), the authors investigated the implications of differences in body fat for dating and sexual activity and the implications of heterosexual activity for dieting and weight concerns. Among White girls, and Black girls with college-educated mothers, more body fat was associated with a lower probability of dating, even among nonobese girls. However, dating and sexual experience were unrelated to subsequent dieting and weight concerns. For both Blacks and Whites, body fat was the key determinant of dieting, weight dissatisfaction, and eating concerns. These findings indicate that adolescent girls' concerns about weight have a basis in real experiential differences, and efforts to promote healthy attitudes and eating habits may be more effective if the experiential implications of weight differences are taken into account.

Monthly measures of salivary testosterone predict sexual activity in adolescent males.

Strong relationships between one-time serum testosterone (T) measures and sexual activity have been demonstrated in cross-sectional analyses of adolescent males. However, a subsequent longitudinal study of a separate adolescent sample, using semiannual plasma measures, failed to replicate cross-sectional findings. The present study reexamined the relationship between T and sexual activity using more frequently collected measures of salivary T and behavior. Saliva samples and weekly behavior checklists were collected over a 2-year period from the same panel sample of males on which semiannual analyses were based. Saliva samples representing measures approximately every fourth week of study participation were selected for T assay. The association between these monthly salivary T measures and weekly reports of incidents of sexual activity was assessed with repeated measures analyses. Higher levels of salivary T were significantly associated with an increasing hazard of coital initiation, and with more frequent coital and noncoital activity. Within-individual change analyses demonstrated that increases in salivary T were associated with increased sexual activity. Comparisons of models that varied specimen type, schedule of T measurement, and type of behavioral report indicated that all three factors contribute to the varying magnitude of hormone/behavior relationships that are demonstrated. These findings are consistent with a biosocial model of adolescent sexual development that pubertal changes in T are a causal factor in the timing of sexual initiation and the frequency of activity during adolescence.

Testosterone predicts initiation of coitus in adolescent females.

OBJECTIVE: The purposes of this study were to demonstrate, using longitudinal data, that the pubertal rise in testosterone (T) is associated with subsequent increases in female sexual interest and activity, and to examine these relationships within the context of a social control variable. METHODS: Using data from a 2-year panel study of approximately 200 black and white postmenarcheal adolescent females, the relationships among semiannual measures of T, sex hormone binding globulin (SHBG), pubertal development, and self-reports of coital and noncoital sexual activity were assessed. RESULTS: Testosterone and changes in T were significantly related to the timing of subsequent transition to first coitus for blacks and whites. Frequency of attendance at religious services operated as a social control variable among white females, and was found to moderate T effects on sexual transition for this group. CONCLUSIONS: These results are consistent with a biosocial model proposing T as a causal factor in female sexual activity, and suggest that biological effects are moderated by relevant social variables.

Testosterone and religiosity as predictors of sexual attitudes and activity among adolescent males: a biosocial model.

A biosocial model of the effects of early adolescent testosterone levels and religiosity on adolescent males' sexual attitudes and activity over a 3-year period was examined. Using panel data for approximately 100 boys who were 12.5/13.0 years old at study entry, significant additive effects of free testosterone and frequency of attendance at religious services were demonstrated on the transition to first intercourse and other aspects of sexual behaviour and attitudes. No interactive effects of the two predictors were found. Boys with higher free testosterone levels at study entry who never or infrequently attended religious services were the most sexually active and had the most permissive attitudes. Boys with lower free testosterone who attended services once a week or more were the least active and reported the least permissive attitudes. For some behaviours, differences between free testosterone/attendance groups increased over time, resulting in substantial behavioural differences by the final round of measurement 3 years later.

Effects of repeated questionnaire administration in longitudinal studies of adolescent males' sexual behavior.

By comparing four similar groups of young adolescent males who completed questionnaires about their sexual behavior different numbers of times at various intervals, we explore the hypothesis that repeated questionnaire completion will affect sexual behavior. We find little support for the hypothesis even when the number of questionnaire administrations is very high.

Testosterone and pubertal development as predictors of sexual activity: a panel analysis of adolescent males.

Strong cross-sectional relationships between testosterone (T) and sexual activity have been found for human adolescent males, even when level of pubertal development is controlled; however, it has not been demonstrated that sexual behavior increases over time as a consequence of hormonal changes. The purpose of this paper was to extend previous cross-sectional findings by demonstrating that sexual behavior is initiated and increases within individuals over time as a direct function of changes in T levels, rather than indirectly through pubertal development. Analyses are based on a 3-year panel study of about 100 7th- and 8th-grade adolescent boys. Pubertal development and changes in pubertal development were significantly and positively related to changes in sexual ideation, noncoital behavior, and to the transition to sexual intercourse. Testosterone levels at study entry were significantly related to coital status at Time 1 and also predicted the transition to nonvirgin status. However, changes in hormone levels during the 3 years of study participation did not predict changes in ideation or noncoital sexual activity, regardless of the period of change or the lag time to effects. The panel data suggest, in contrast to earlier cross-sectional results, that change in pubertal development is related to the initiation of sexual activity because of its social stimulus value, and not solely because it is determined by, or is a proxy for, changing hormone levels. Possible causes of the different findings in the cross-sectional and panel data are examined, and the implications and meaning of hormone/behavior relationships based on single measures are discussed.

Relationships between aggression and pubertal increases in testosterone: a panel analysis of adolescent males.

Existing data linking testosterone (T) and aggression in human adult males are surprisingly tenuous. In one of the few studies based on adolescent males, Olweus et al. (1988) demonstrated strong relationships between concurrent measures of T and aggression. However, the conclusions that could be drawn regarding developmental change were limited. Using data from a three-year panel study of 100 adolescent males (ages 12 to 13 at study entry), we examined whether there are significant relationships between concurrently collected measures of T and self-ratings of aggression, and whether the dramatic pubertal rise in T predicts subsequent change in aggression ratings. Panel analyses incorporating concurrent, lagged, and change measures found few significant relationships between aggression and T or pubertal development. The general absence of T/aggression relationships is discussed in the context of other empirical findings, the aggression measures used, and prepubertal differentiation on aggression.

The relationship of respiratory complications from gastroesophageal reflux to prematurity in infants.

The association between respiratory complications of gastroesophageal reflux (GER) and prematurity in infants has not been described completely. We studied 82 consecutive infants less than 6 months of age with major respiratory symptoms suspected to be caused by GER. Twenty-eight patients had bronchopulmonary dysplasia (BPD). Extended (18 to 24 hours) esophageal pH monitoring was used to document GER with a pH score. Respiratory complications were considered to be caused by GER if a prolonged mean duration of sleep reflux (ZMD) was found. Seventy-five of the 82 (91%) infants had documented GER, but only 45 (55%) had a prolonged ZMD. The incidence of GER was high regardless of the gestational age at birth, postconceptual age at time of study, and the presence of BPD. The incidence of a prolonged ZMD was higher in infants who were 34 to 39 weeks' gestation (10/12, 83%) than in infants who were less than 34 weeks' gestation at birth (15/37, 41%; P = .01). The incidence of a prolonged ZMD was lowest in infants 39 weeks or less postconceptual age at the time of study (4/14, 29%; P = .017). Most infants with BPD did not have a prolonged ZMD (12/28, 43%). However, 11 of the 12 (92%) infants with BPD and a prolonged ZMD showed dramatic improvement after effective antireflux therapy compared with 0 of 16 infants with BPD and normal ZMD (P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)