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PubMed2005

The interaction role of obesity and pubertal timing on the psychosocial adjustment of adolescent girls: longitudinal data.

OBJECTIVE: The objective of the study was to verify the hypothesis that obesity is associated with pubertal timing, as both factors interact to predict psychosocial adjustment problems in girls. SUBJECTS: We selected 811 girls who had participated in a longitudinal study on a representative sample of French Canadian children from 1986 to 1997. METHOD: Only data collected between 1993 and 1996 were analyzed. We classified the participants into three weight categories (normal, overweight, and obese) and pubertal timing (early, on-time, or late-maturing) and compared their internalized and externalized problem behavior and conflict as well as their socioeconomic status. RESULT: We found that (1) early and late-maturing girls are more at risk of being overweight during the whole period of pubertal development as demonstrated by the increasing rate of obesity in these two groups between 11 and 13 y old, and (2) there was an interaction effect between pubertal timing and obesity in predicting problem behavior and conflict. Overweight and obese girls who developed faster or slower than their peers displayed more adjustment problems at 11 and 12 y old. At 13 y old, obesity predicted adjustment problems separately without regard to pubertal timing. Our results suggest that puberty timing is a risk factor for obesity and that both pubertal timing and being overweight predict adjustment problems during all the courses of pubertal development, supporting partially our hypothesis. CONCLUSION: Programs and interventions must take into account these two factors and adolescents should be monitored throughout all the periods of pubertal development.

Adaptation, Psychological↗
PubMed2003

A model for clustering of longitudinal data sets of infant mortality rates in India.

BACKGROUND: Cluster analysis is used to assign a set of observations into clusters that have similar characteristics as measured by a set of classifying variables. There have been few studies on clusters of longitudinal datasets or the mathematical and statistical modeling of partitioning of time trends. We present a model to cluster the infant mortality rate trends for 14 major states of India from 1972 to 1998. MATERIAL/METHODS: Each state is represented as an nth degree polynomial using the curvilinear regression method. The total difference in the rate of change from time t1 (1972) to tn (1998) for each state is obtained by summing the differences in velocity between two adjacent time points (1), and the Euclidean distance of the trend from the base is calculated objectively by dividing the trend into the optimum number of divisions (2). By adding these two (1 & 2), the measure of dissimilarity coefficient is obtained, which is finally used to cluster the trends. RESULTS: In this case, all three methods, i.e. complete linkage, average between groups, and Ward's linkage method (using SPSS 10.0), suggested the same number and type of clusters. Cluster I has only one state, Cluster II consists of four states, Cluster III has eight states, and Cluster IV has only one state. CONCLUSIONS: Such clustering and grouping gives much more confidence to planners in devising strategies for the control of infant mortality and resource allocation at the national level.

Cluster Analysis↗
PubMed2003

A comparison of group sequential methods for binary longitudinal data.

Interim analyses are conducted to allow for early termination of the trial, for ethical as well as economical reasons. Here we consider interim analyses in repeated measurements studies where the measurements are binary. Two methods for analysing this kind of data are compared according to their operating characteristics. A subject-specific approach based on the logistic random-effects model is compared with the population-averaged approach based on the generalized estimating equations. The comparison is illustrated with simulations using a randomized clinical trial for toenail fungal infection.

Antifungal Agents↗
PubMed1980

[Longitudinal data of physical growth of healthy children. V. Acromial, radial, styleoideal, daktylion, ileospinal, tibial and medial malleolus heights of children aged 2.5 to 15 years (author's transl)].

From 1968--1978 a longitudinal study was performed concerning development of acromial, radial, styleoideal, daktylion, ileospinal, tibial and medial malleolus heights in 709 boys and 711 girls aged 2.5 to 15 years. During time studied, mean increases in boys amounted in acromial height to 70.0 cm, in radial height to 53.8 cm, in styleoideal height to 41.5 cm, in daktylion height to 33.4 cm in ileospinal height to 52.0 cm, in tibial height to 25.4 cm and in medial malleolus height to 3.8 cm. Corresponding data in girls amounted to 62.8 cm, 49.3 cm, 42.4 cm, 31.2 cm, 46,7 cm, 22.4 and 3.2 cm. Boys had a more intensive development of heights than girls except for styleoideal height. The heights measured developed almost linearly in boys and girls 4 to 10 years old. Development of heights decreased in 11 and 12 years old boys and increased again with year 13. In girls, intensity of growth decreased beginning with year 13.

Adolescent↗
PubMed1980

[Longitudinal data of physical growth of healthy children. III. Circumferences of thorax, upper arm, thigh and calf of children aged 2 to 15 years (author's transl)].

From 1968--1978 a longitudinal study was performed concerning development of thorax, upper arm, thigh and calf circumferences in 709 boys and 711 girls 2--15 years old. In boys the mean increase in thoracic circumference amounted to 32.9 cm, in upper are circumference to 8.3 cm, in thigh circumference to 20.6 cm and in calf circumference to 13.0 cm. The corresponding circumferences in girls amounted to 30 cm, 7.9 cm, 22.4 cm and 12.7 cm. In boys the circumferences developed almost linearly until year 15. Girls had the same linear development until year 13. Between years 14 and 15 girls had in increased development of all circumferences studied.

Adolescent↗
PubMed1995

Longitudinal data on growth and final height in diabetic children.

The available data on growth in children with insulin-dependent diabetes mellitus are conflicting and are mainly derived from cross-sectional studies. In this longitudinal study, height, weight, skeletal age, and pubertal development were recorded until final height was attained in 46 children (22 girls and 24 boys) with onset of diabetes before the age of 10 y. At the onset of diabetes, height SD score (SDS) averaged 0.41 in girls and 0.56 in boys, which was normal when corrected for the secular trend. Prepubertal growth was unaffected in both sexes. Diabetic boys had a marked delay in onset of puberty (mean age at genitalia stage 2: 13.7 y) but attained a normal final height (final height SDS: 0.48 +/- 0.89). In girls final height was slightly reduced (height SDS 0.27 +/- 0.97) due to a suboptimal pubertal growth spurt. Mean pubertal height gain in girls was 16.6 cm and mean age at breast stage 2 was 11.6 y. Diabetic girls also tended to become obese during puberty. Skeletal maturation was normal at all ages. These data suggest that conventional therapy does not guarantee optimal growth, especially in girls.

Adolescent↗
PubMed1994

Analysis of longitudinal data: random coefficient regression modelling.

We review random coefficient regression (RCR) models and methods for fitting these models from an applications perspective. Methods for data with exponential family distributions are presented with the Gaussian distribution as a special case. Attention is given to interpretation of fixed effects and the correlation structures implied by RCR models. Estimation methods are presented wtih computational approaches. Problems associated with testing fixed effects include accurate variance estimation and robustness to misspecification of the covariance structure. Methods for model selection and assessment are presented. An example is used to demonstrate recommended approaches.

Adult↗
PubMed2005

Joint modelling of bivariate longitudinal data with informative dropout and left-censoring, with application to the evolution of CD4+ cell count and HIV RNA viral load in response to treatment of HIV infection.

Several methodological issues occur in the context of the longitudinal study of HIV markers evolution. Three of them are of particular importance: (i) correlation between CD4+ T lymphocytes (CD4+) and plasma HIV RNA; (ii) left-censoring of HIV RNA due to a lower quantification limit; (iii) and potential informative dropout. We propose a likelihood inference for a parametric joint model including a bivariate linear mixed model for the two markers and a lognormal survival model for the time to drop out. We apply the model to data from patients starting antiretroviral treatment in the CASCADE collaboration where all of the three issues needed to be addressed.

Anti-HIV Agents↗
PubMed1994

Psychosocial, behavioral, and medical outcomes in children with epilepsy: a developmental risk factor model using longitudinal data.

OBJECTIVE: We studied factors predicting the risk of adverse long-term psychosocial, behavioral, and medical outcomes in children with epilepsy. METHODS: Children (N = 157, 4.5 to 13 years) were enrolled in a prospective longitudinal study when first seen. Potential subjects were excluded if they were moderately or severely mentally retarded, had motor or sensory handicaps interfering with testing, or did not speak either English or Spanish. MEASURES: To develop risk predictors, we collected information regarding the child's medical and seizure history, cognitive functioning, and behavior problems, and family functioning. Children and their families were followed for a minimum of 18 months, then underwent reassessment of medical status, parent's attitudes toward epilepsy, and the child's behavioral and cognitive functioning. Data were analyzed by confirmatory factor analysis to develop baseline factors (Sociocultural Risk, Seizure Risk, and Behavior Problems) and outcome factors (Medical/Seizure Problems, Parent's Negative Attitudes Toward Epilepsy, and Behavior Problems), followed by structural equation modeling to determine across-time causal effects. Eighty-eight subjects completed all baseline and outcome measures. RESULTS: Among significant across-time effects, Medical Outcome was predicted by Seizure Risk. An increased number of stressful life events predicted better Medical Outcome. Low acculturation increased Parent's Negative Attitudes and was associated with increased Behavior Problems at baseline. Behavior Problems were stable across time. It is interesting that IQ did not affect any of the outcomes, although its effect may have been mediated through other baseline measures. CONCLUSIONS: Seizure history was the best predictor of ongoing medical difficulties, whereas the most important causes of ongoing parental anxiety and negative attitudes toward epilepsy were sociocultural. Variation in medical or attitudinal outcomes was not influenced by either the child's IQ or reported behavioral problems. These findings suggest that to alter attitudes toward epilepsy, programs should be tailored to the sociocultural background of the family. Studies of quality of life of children with epilepsy should include appropriate sociocultural measures.

Acculturation↗
PubMed1980

[Longitudinal data of physical growth of healthy children. IV. Shoulder breadth, thorax breadth, thorax depth, hand breadth, 2 pelvic and epicondylic breadths of children aged 2.5 to 15 years (author's transl)].

From 1968--1978 a longitudinal study was performed concerning development of shoulder and thorax breadths, thorax depth, breadths of hand, pelvis, humeral and femoral epicondylus in 709 boys and 711 girls aged 2.5 to 15 years. During time studied mean increases in boys amounted in shoulder breadth to 15.1 cm, in thorax breadth to 9.8 cm, in thorax depth to 6.6 cm, in hand breadth to 3.1 cm, in breadths of pelvis I to 10.9 cm, of pelvis II to 8.5 cm, in breadth of humeral epicondylus 2.5 cm and of femoral epicondylus 3.5 cm. The corresponding data in girls amounted to 14.0 cm, 8.0 cm 4.8 cm, 2.5 cm, 11.0 cm, 8.0 cm, 2.0 cm and 2.9 cm. The parameter measured developed both in boys and girls almost linearly until year 12. Beginning with year 13, development of breadths increased in boys are remained unchanged in girls. Development of breadth in boys was always increased compared with girls except pelvic breadth I.

Adolescent↗
PubMed2000

Latent variable models for longitudinal data with multiple continuous outcomes.

Multiple outcomes are often used to properly characterize an effect of interest. This paper proposes a latent variable model for the situation where repeated measures over time are obtained on each outcome. These outcomes are assumed to measure an underlying quantity of main interest from different perspectives. We relate the observed outcomes using regression models to a latent variable, which is then modeled as a function of covariates by a separate regression model. Random effects are used to model the correlation due to repeated measures of the observed outcomes and the latent variable. An EM algorithm is developed to obtain maximum likelihood estimates of model parameters. Unit-specific predictions of the latent variables are also calculated. This method is illustrated using data from a national panel study on changes in methadone treatment practices.

Longitudinal Studies↗
PubMed1977

Stature and body weight growth patterns from longitudinal data of Japanese children born during World War II.

Stature and body weight data of 100 boys and 100 girls from 7 to 17 years of age in Shimodate City who were born during World War II were longitudinally analyzed. The children were significantly smaller and lighter throughout their growth period than those born 11 years after the end of the war. The correlation coefficient between statures at each age and at age 17 showed a gradual increase with increasing age, while that between statures at each age and at age 7 decreased with age. However, a drop in the correlation coefficient was found during puberty, at age 11 for girls and at age 13 for boys. Comparing the normalized distance from mean values of stature and body weight at age 7, at puberty, and at age 17, only 51% of the children continued to be in the same relative position for both height and weight, 6% of boys and 4% of girls showing a decreasing pattern for both and 4% of boys and 7% of girls showing an increasing pattern for both. Thus, about 60% of the children of either sex presented parallel stature and body weight growth patterns for ages from 7 to 17.

Adolescent↗
PubMed1993

Stability and change of interest in obstetrics-gynecology among medical students: eighteen years of longitudinal data.

PURPOSE: To compare the percentage of students who maintain interest in specializing in obstetrics-gynecology during medical school with the percentages of students maintaining interest in other selected specialties, and to examine changes of interest from obstetrics-gynecology to other specialties and from other specialties to obstetrics-gynecology. METHOD: A longitudinal cohort study comparing the stabilities of students' interests in obstetrics-gynecology and in other specialties was performed by using data on 3,889 graduates of 18 classes of Jefferson Medical College of Thomas Jefferson University between 1975 and 1992. RESULTS: The percentage of students who maintained interest in obstetrics-gynecology, as measured at the beginning and end of medical school, was 19%, compared with 40% for internal medicine and surgery, 39% for family medicine, and 22% for pediatrics. By the time they graduated, some students who had planned as freshman to pursue obstetrics-gynecology had changed their interests to internal medicine (19%), surgery (17%), family medicine (8%), or pediatrics (7%). In turn, obstetrics-gynecology attracted students who had initially expressed interest in other specialties: 17% from family medicine, 14% from surgery, 12% from internal medicine, and 8% from pediatrics. Despite the low percentage of students who maintained interest in obstetrics-gynecology, the overall percentage of students interested in obstetrics-gynecology at the time of graduation was somewhat greater than the percentage of students interested at the start of medical school. CONCLUSION: That only about one-fifth of the students initially interested in obstetrics-gynecology maintained their interest, and that many students' interests changed from one specialty to another, suggest that factors contributing to changes in interest need further investigation.

Career Choice↗