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Biomedical subjects

J R Udry

Publications and source records attributed to J R Udry.

At least 19 recordsLinked to original sources
PubMed1998

Adolescent obesity increases significantly in second and third generation U.S. immigrants: the National Longitudinal Study of Adolescent Health.

Little is known concerning obesity patterns of ethnic subpopulations in the U.S. and the effects of acculturation on these patterns. Adolescent obesity, a major public health problem, has important health, social and economic consequences for the adolescent. The National Longitudinal Study of Adolescent Health survey is unique in the size of the adolescent sample and in its ability to provide large representative samples of Anglo, African-American, Hispanic and Asian-American adolescents. A nationally representative sample of 13,783 adolescents was studied. Measurements of weight and height collected in the second wave of the survey were used to study adolescent obesity. Multivariate logit techniques were used to provide an understanding of the ethnic, age, gender and intergenerational patterns of adolescent obesity. Comparisons are presented between the NHANES III results and those from the Adolescent Health Survey. The smoothed version of the NHANES I 85th percentile cut-off was used for the measure of obesity in this paper. For the total sample, 26.5% were obese. The rates were as follows: white non-Hispanics, 24.2%; black non-Hispanics, 30.9%; all Hispanics, 30.4%; and all Asian-Americans, 20.6%. Important variations within the Hispanic and Asian-American subpopulations are presented. The Chinese (15.3%) and Filipino (18.5%) samples showed substantially lower obesity than non-Hispanic whites. All groups showed more obesity among males than among females, except for blacks (27.4% for males and 34.0% for females). Asian-American and Hispanic adolescents born in the U.S. are more than twice as likely to be obese as are first generation residents of the 50 states.

Acculturation↗
PubMed1997

Protecting adolescents from harm. Findings from the National Longitudinal Study on Adolescent Health.

CONTEXT: The main threats to adolescents' health are the risk behaviors they choose. How their social context shapes their behaviors is poorly understood. OBJECTIVE: To identify risk and protective factors at the family, school, and individual levels as they relate to 4 domains of adolescent health and morbidity: emotional health, violence, substance use, and sexuality. DESIGN: Cross-sectional analysis of interview data from the National Longitudinal Study of Adolescent Health. PARTICIPANTS: A total of 12118 adolescents in grades 7 through 12 drawn from an initial national school survey of 90118 adolescents from 80 high schools plus their feeder middle schools. SETTING: The interview was completed in the subject's home. MAIN OUTCOME MEASURES: Eight areas were assessed: emotional distress; suicidal thoughts and behaviors; violence; use of 3 substances (cigarettes, alcohol, marijuana); and 2 types of sexual behaviors (age of sexual debut and pregnancy history). Independent variables included measures of family context, school context, and individual characteristics. RESULTS: Parent-family connectedness and perceived school connectedness were protective against every health risk behavior measure except history of pregnancy. Conversely, ease of access to guns at home was associated with suicidality (grades 9-12: P<.001) and violence (grades 7-8: P<.001; grades 9-12: P<.001). Access to substances in the home was associated with use of cigarettes (P<.001), alcohol (P<.001), and marijuana (P<.001) among all students. Working 20 or more hours a week was associated with emotional distress of high school students (P<.01), cigarette use (P<.001), alcohol use (P<.001), and marijuana use (P<.001). Appearing "older than most" in class was associated with emotional distress and suicidal thoughts and behaviors among high school students (P<.001); it was also associated with substance use and an earlier age of sexual debut among both junior and senior high students. Repeating a grade in school was associated with emotional distress among students in junior high (P<.001) and high school (P<.01) and with tobacco use among junior high students (P<.001). On the other hand, parental expectations regarding school achievement were associated with lower levels of health risk behaviors; parental disapproval of early sexual debut was associated with a later age of onset of intercourse (P<.001). CONCLUSIONS: Family and school contexts as well as individual characteristics are associated with health and risky behaviors in adolescents. The results should assist health and social service providers, educators, and others in taking the first steps to diminish risk factors and enhance protective factors for our young people.

Adolescent↗
PubMed1995

Childhood precursors of age at first intercourse for females.

Age at first intercourse for a sample of adult white women using variables measured during childhood is predicted. Childhood predictors were measured at birth, and ages 5 and 9-11, using existing public-use data on the women. Median age at first intercourse for the sample was 17.5 years. Early family predictors, early developmental characteristics, and temperamental characteristics during childhood together could predict about a fourth of the variance in age at first intercourse. The strongest predictors were motor skills and nightmares at age 5, church attendance with family at age 9, and domineering and mature personality at age 9.

Adolescent↗
PubMed1995

Stress and age at menarche of mothers and daughters.

The hypothesis that psychological stress during early childhood leads to advanced reproductive maturation was assessed using data from the California Childhood Health and Development Study. Regression analyses failed to indicate that bed wetting, nightmares or thumb-sucking at age 5 predict age at menarche, regardless of controls for mother's age at menarche. Among socioeconomic variables suggested as contextual stressors measured at age 9-11 only mother's education was a significant predictor of daughter's age at menarche, though its effect is trivial compared to mother's age at menarche. Path analysis on a subsample of the subjects failed to demonstrate the hypothesised indirect effect of mother's age at menarche on daughter's age at menarche acting through early marriage and marital dissolution. These results cast doubt on the theory that early childhood stress is the key to divergent reproductive strategies among females based on the timing of reproductive maturation.

California↗
PubMed1995

Androgen effects on women's gendered behaviour.

Test of the applicability of the hormonal theory of sex-dimorphic behaviour to adult women is achieved in this study by assembling measures of prenatal and adult androgen exposure, and a broad measure of gendered behaviour on a sample of white women aged 27-30. Androgen exposure in the second (and no other) trimester of fetal life, combined with and in interaction with adult androgens, masculineses women's behaviour and explains a substantial proportion of the within-sex variance in women's adult gendered behaviour.

Adult↗
PubMed1994

Implications of hormonal influences on sexual behavior for demographic models of reproduction.

In exploring the implications of hormonal influences on sexual behavior for reproduction, we have focused on androgens because of the convincing evidence for androgenic effects on female sexual motivation. We have been guided by the simple idea, based on clinical findings among hyperandrogenic women, that higher testosterone levels will increase female sexual motivation which in turn will result in increased coital frequency. However, careful consideration of the evidence fails to confirm such a role for testosterone in sexual behavior among normal women at any point in the reproductive span. While some amount of testosterone appears to be important in maintaining female sexual motivation, there is little evidence that variation in testosterone within the normal range is associated with variation in sexual motivation. Reported associations between testosterone and sexual behavior among married women cannot be interpreted as resulting from androgenic effects on sexual motivation. Thus we are left with the task of explaining why testosterone does not appear to play the same role in libido among hyperandrogenic and normal women. As mentioned earlier, some of the difference may attributable to the much higher levels of testosterone among hyperandrogenic women. Sherwin points out that the levels of sexual motivation decline with declining testosterone levels even while testosterone is well above normally occurring levels. It is possible that the brain is simply not sensitive to the variation in testosterone levels found in normal women. Other evidence suggests that the presence of intact ovaries may be equally important. A recent study of androgen replacement in naturally post-menopausal women failed to find a dramatic effect of testosterone on sexual motivation and behavior, despite levels similar to those in studies on surgically menopausal women, pointing to the importance of other factors associated with the presence of ovaries. A similar point can be made with regard to hyperandrogenism related to endogenous sources of testosterone, as in the case of PCOS. High levels of testosterone effectively disrupt ovarian function and interfere with other ovarian processes. Among hyperandrogenic women sexual behavior appears to be related to the direct effects of androgens on motivation, while the indirect effects of estrogen and progesterone are essentially eliminated. Among normal women, on the other hand, there is little evidence for such a dominating role of a direct androgenic effect on sexual behavior. Instead, other ovarian hormones, including estrogen and progesterone may also play a demonstrable role, despite the lack of strong evidence at this point.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1994

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.

Adolescent↗
PubMed1994

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.

Adolescent↗
PubMed1994

The nature of gender.

I explain a biosocial model of women's gendered behavior (behavior on which the sexes differ). This model integrates a macro sociological theory with a biological theory derived from primate behavior. The sociological model is designed to explain changes in the relationship between sex and behavior over time or between groups. The biological model is designed to explain individual within-sex variance and between-sex variance in gendered behavior in a cohort. Results from an original study are presented to demonstrate that within-sex variance in women's gendered behavior is explained well by the primate model. I conclude that human nature is gendered. The implications of this conclusion are explored for demographic and other social science research.

Adolescent↗
PubMed1993

Determinants of coitus after childbirth.

Using a sample of 3080 women from Cebu, Philippines, interviewed immediately after childbirth and every 2 months thereafter for 2 years, the determinants of return to coitus are analysed. Eighty per cent of the women returned to coitus before the return of menses, and 90% did so before stopping breast-feeding. In hazards models, variables associated with traditional life styles retarded return to coitus. Situational variables (husband resident, crowding, children aged 6 and under), especially husband residence, and biological variables (mother's age, return to menses, and lactation) were significant predictors of return to coitus. The implications of the analysis for the construction of models of birth interval dynamics are discussed.

Adult↗
PubMed1993

Nutrition, lactation, and birth spacing in Filipino women.

The Cebu Longitudinal Health and Nutrition Survey is used to examine the roles of women's nutrition and infant feeding in determining time from birth to menses and time from menses to conception. The analysis sample includes 2,648 Filipino women followed for 24 months postpartum. Recently devised statistical estimation techniques to control for unobserved heterogeneity and endogeneity are employed in estimating a two-state hazard model. Low body mass index and lower dietary fat intake are associated with increased duration of postpartum amenorrhea. Contraceptive use, high dietary fat consumption, higher parity, and absence of spouse predict a longer waiting time to conception once menses have returned. Simulation of the hazard model is used to examine the effects of the key nutrition and lactation factors.

Adolescent↗
PubMed1991

Predicting alcohol use by adolescent males.

An attempt was made to predict alcohol use among 101 American white boys aged 13-16. The model combined genetic and social variables. The analysis revealed evidence of a genotype-environment interaction and thus the use of either the biological or social variables alone poorly predicts alcohol use.

Adolescent↗
PubMed1989

Demographic components of seasonality of pregnancy.

Previous studies of the seasonality of pregnancy and birth have typically been based on monthly numbers or proportions of pregnancies or births (i.e. their distribution throughout the year) without any explicit accounting of the size of the population actually at risk of pregnancy by month. From data on monthly populations at risk and monthly probabilities of pregnancy this paper determines the relative contribution of each component to the monthly distribution of pregnancies. The data come from the National Survey of Family Growth, Cycle III. While there is some seasonality in the size of the at-risk population, it contributes little to the overall monthly variation of pregnancy, which is determined mainly by seasonality of pregnancy probability (fecundability).

Coitus↗
PubMed1988

Sex hormone effects on personality at puberty.

In this study we use serum steroid hormone assays and Adjective Check List responses from a representative sample of 102 male and 99 female adolescents to examine the relations between hormones, personality, and sexual behavior. We address two questions: (a) Does pubertal testosterone (T) cause sex dimorphism in personality? (b) Do pubertal hormones affect sexual behavior indirectly through effects on personality? Exploratory factor analysis of the Adjective Check List generated a factor common to male and female adolescents that correlated highly with T. However, male and female subjects did not differ in their mean level on this factor or in the correlation of this factor with T. In spite of the large sex difference in T, the girls were much more sensitive than the boys on the extracted factor to differences in T. We conclude that the answer to both questions is probably no.

Adolescent↗
PubMed1987

Marital sex frequency and midcycle female testosterone.

The purpose of the study was to attempt to replicate a finding of Persky et al. (1978) that midcycle peak values of testosterone (T) in women predicted differences in frequency of intercourse among married couples. Luteinizing hormone (LH), total testosterone (TT), and free testosterone (FT) values from 10 to 14 daily midcycle blood samples donated by 43 volunteering wives were analyzed against sexual activity patterns reported by the couples over a longer period of time. All couples were contracepting by means other than exogenous hormones or the rhythm method. Each morning through three menstrual cycles husbands and wives recorded independently and on separate forms answers to a series of questions concerning sexual activity in the previous 24 hr. Wives also recorded basal body temperatures (BBT). We designated midcycle values of TT and FT according to several definitions of midcycle. Total testosterone levels at the day of the BBT nadir and the day before the nadir correlated significantly with average intercourse frequency. Correlations with FT were statistically significant regardless of which midcycle measure was used; the day before the BBT nadir gave the highest correlation, 0.618, p = 0.01. Mean testosterone (TT or FT) values were not significantly related. We conclude that female midcycle total testosterone or free testosterone is indexing some unobserved event that affects the frequency of intercourse of couples. We speculate that this event affects the motivation of females, which influences the set point of the compromise frequency characteristic of couples.

Adult↗
PubMed1987

Peak coital rate coincides with onset of luteinizing hormone surge.

Twenty-five married women who were not using contraceptives provided daily urine specimens and coital reports for at least 90 days. The authors used urinary luteinizing hormone (LH) as a hormonal marker to determine ovulatory phase, onset of LH surge day, and LH peak day. Coital rate was elevated during the ovulatory phase of the menstrual cycle. Peak coital rate (0.72) occurred on onset of LH surge day, and was significantly greater (P less than 0.05) than the mean rate (0.44 +/- 0.06) across the entire menstrual cycle. The authors discuss possible social and hormonal mechanisms that might underlie an ovulatory peak in coitus, as well as the relevance of their findings to current models of fecundability.

Adult↗