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At least 631 records · Page 35Linked to original sources
PubMed1998

The determinants of child mortality in the Philippines: estimation of a structural model.

"This paper employs a longitudinal data set from the Philippines to estimate a structural model of the determinants of infant mortality. To control for the endogeneity of some explanatory variables, a set of reduced form equations for these outcomes is estimated simultaneously with the mortality hazard. A non-parametric discrete factor method is used to control for common unobservable factors in the error terms. Birth interval and parity lose explanatory power once biological measures are considered in the model. The results indicate significant correlations across the equations' error terms. The significant effects of breastfeeding and growth on mortality are quantified in simulation experiments." The data are from a longitudinal survey conducted in metropolitan Cebu between 1983 and 1986.

Asia↗
PubMed2003

Latent change models of adult cognition: are changes in processing speed and working memory associated with changes in episodic memory?

The authors used 6-year longitudinal data from the Victoria Longitudinal Study (VLS) to investigate individual differences in amount of episodic memory change. Latent change models revealed reliable individual differences in cognitive change. Changes in episodic memory were significantly correlated with changes in other cognitive variables, including speed and working memory. A structural equation model for the latent change scores showed that changes in speed and working memory predicted changes in episodic memory, as expected by processing resource theory. However, these effects were best modeled as being mediated by changes in induction and fact retrieval. Dissociations were detected between cross-sectional ability correlations and longitudinal changes. Shuffling the tasks used to define the Working Memory latent variable altered patterns of change correlations.

Aged↗
PubMed2003

Automatic analysis of longitudinal growth data on the Website willi-will-wachsen.de.

Many disorders of child development can only be treated successfully when they are detected early. Thus, child development should be checked periodically. Usually, a few parameters are sufficient to check whether or not a child is developing normally in terms of growth. By making such checks publicly available on the website: willi-will-wachsen.de the authors hope to provide a tool which helps the automatization of simple check procedures and thereby detect with less effort more children with growth disorders.

Adolescent↗
PubMedDate not supplied

On correlations between adjacent velocities and accelerations in longitudinal growth data.

Correlations are examined between adjacent velocity and acceleration growth in stature, weight and skinfold thickness in a group of adolescent boys measured approximately quarterly. It is concluded that some substantial component of the variability behaves rather like measurement error, and this is likely to represent negative feedback homeostasis.

Acceleration↗
PubMed2004

Analysis of longitudinal metabolomics data.

MOTIVATION: Metabolomics datasets are generally large and complex. Using principal component analysis (PCA), a simplified view of the variation in the data is obtained. The PCA model can be interpreted and the processes underlying the variation in the data can be analysed. In metabolomics, often a priori information is present about the data. Various forms of this information can be used in an unsupervised data analysis with weighted PCA (WPCA). A WPCA model will give a view on the data that is different from the view obtained using PCA, and it will add to the interpretation of the information in a metabolomics dataset. RESULTS: A method is presented to translate spectra of repeated measurements into weights describing the experimental error. These weights are used in the data analysis with WPCA. The WPCA model will give a view on the data where the non-uniform experimental error is accounted for. Therefore, the WPCA model will focus more on the natural variation in the data. AVAILABILITY: M-files for MATLAB for the algorithm used in this research are available at http://www-its.chem.uva.nl/research/pac/Software/pcaw.zip.

Algorithms↗
PubMed2001

Well-being as a moving target: measurement equivalence of the Bradburn Affect Balance Scale.

Although the Bradburn Affect Balance scale (ABS) is a frequently used two-factor indicator of well-being in later life, its measurement and invariance properties are not well documented. We examined these issues using confirmatory factor analyses of cross-sectional (adults ages 54-87 years) and longitudinal data from the Victoria Longitudinal Study. Stability of the positive and negative affect factors was moderate across a 3-year period. Overall, factor loadings for positive affect items were invariant over time with the exception of the pleased item. Negative affect items were time invariant. However, age-group comparisons between young-old and old-old groups revealed age differences in loadings for the upset item at Time 1. Finally, gender groups differed in loadings for the top of the world and going your way items. Thus a pattern of partial measurement equivalence characterized item response to the ABS. Our results suggest that group comparisons and longitudinal change in ABS scale scores of positive and negative affect should be interpreted with caution.

Affect↗
PubMed1998

Time series analysis in historiometry: a comment on Simonton.

Time series analysis (TSA) is one of a number of new methods of data analysis appropriate for longitudinal data. Simonton (1998) applied TSA to an analysis of the causal relationship between two types of stress and both the physical and mental health of George III. This innovative application demonstrates both the strengths and weaknesses of time series analysis. Time series is applicable to a unique class of problems, can use information about temporal ordering to make statements about causation, and focuses on patterns of change over time, all strengths of the Simonton study. Time series analysis also suffers from a number of weaknesses, including problems with generalization from a single study, difficulty in obtaining appropriate measures, and problems with accurately identifying the correct model to represent the data. While careful attempts are made to minimize these problems, each is present in the Simonton study, although sometimes in a subtle manner. Changes in how the data could be gathered are suggested that might help to solve some of these problems in future studies. Finally, the advantages and disadvantages of employing alternative methods for analyzing multivariate time series data, including dynamic factor analysis, are discussed.

Data Interpretation, Statistical↗
PubMed1989

Economic well-being following marital termination: a comparison of widowed and divorced women.

Several studies of divorced and widowed women show increased odds of becoming poor following the termination of marriage. Both cross-sectional and longitudinal data suggest that the end of marriage is correlated with higher poverty rates. Less is know, however, about factors that influence economic well-being over time, and whether these factors are similar for widows and divorced women. This analysis uses data from the National Longitudinal Surveys cohort of mature women (1967-1982) to examine the probability of becoming poor after widowhood or divorce among mid-life women, and factors that seem to influence economic well-being. Findings show that 40% of widows and over 1/4 of divorced women fall into poverty for at least some time during the 1st 5 years after leaving marriage. The type of marital transition experienced by the woman is not a significant factor in economic well-being, but both age and prior economic standing have positive estimated effects.

Age Factors↗
PubMed1999

Do male dropouts benefit from obtaining a GED, postsecondary education, and training?

The authors use longitudinal data from the National Longitudinal Survey of Youth to investigate whether the wage trajectories of male high school dropouts are affected by the acquisition of the General Educational Development (GED) credential, by postsecondary education, and by training. The authors show that acquisition of the GED results in wage increases for dropouts who left school with weak skills, but not for dropouts who left high school with stronger skills. College and training provided by employers are associated with higher wages for male dropouts.

Adolescent↗
PubMed2004

Marriage, impairment, and acceptance in persons with multiple sclerosis.

The purpose of this study was to investigate the relationship between marital status, marital concern, perceived impairment, health-promoting behaviors, and acceptance of disability using cross-sectional and longitudinal data from a sample of persons with multiple sclerosis (MS). We hypothesized that the quality and stability of the marital relationship would influence people's ability to accept their disability and protect from accumulation of impairment over time. Furthermore, men and women would receive dissimilar benefits from marriage. These hypotheses were considered with repeated measures analysis, Pearson correlations, and independent sample t tests of data obtained from a longitudinal study of persons with MS. The findings indicate that acceptance of disability and perceived impairment increase significantly over time for men and women. For men, being married was associated with a greater acceptance of disability and less perceived impairment. Men were more concerned than the women about how MS affected their sexual relationships.

Adaptation, Psychological↗
PubMed2005

The relationship of longitudinal change in reproductive hormones and vasomotor symptoms during the menopausal transition.

CONTEXT: The relationship of reproductive hormones to vasomotor symptoms (VMS) has been incompletely explored, although an increase in such symptoms at midlife and their reduction with hormone therapy suggest a strong and direct relationship. Vasomotor symptoms are reported by 65-76% of women traversing the menopausal transition and are a primary reason for medical intervention during this life stage. OBJECTIVE: The purpose of this report was to relate longitudinal serum concentrations of the reproductive hormones estradiol (E2), FSH, testosterone (T), dehydroepiandrosterone sulfate (DHEAS), and SHBG and the free hormone indices free E2 index (FEI) and free T index (FTI) with the occurrence of VMS in women traversing the menopausal transition. DESIGN AND SETTING: The Study of Women's Health Across the Nation is a multisite, longitudinal, cohort study of the menopausal transition being conducted in community-based groups of women. PARTICIPANTS AND MAIN OUTCOME MEASURES: At baseline, 3302 menstruating women who belonged to one of five ethnic/racial groups were recruited and followed up with annual visits. Frequencies of symptoms (hot flashes, night sweats) for the prior 2 wk and measures of other covariates as well as potentially confounding variables were self-reported in the annual interview. Serum was obtained annually, on d 2-5 of a spontaneous cycle in cycling women or within 90 d of the anniversary of the baseline study visit in noncycling women and assayed for FSH, E2, T, SHBG, and DHEAS. FTI and FEI were calculated. This analysis incorporated available longitudinal data from 3293 women, excluding information collected at or after first report of hormone therapy use or hysterectomy. Data were analyzed using longitudinal marginal logistic regression models and a partial proportional odds model. RESULTS: After adjusting for age, body mass index, and other related covariates, VMS prevalence increased with higher (log)FSH concentrations, and the increase was greater when blood was drawn more than 5 d after menses began. FSH concentrations were positively associated with the frequency of either hot flashes or night sweats, and higher FSH concentrations were associated with greater odds of reporting more frequent symptoms. Vasomotor symptom prevalence decreased with higher (log)E2, (sqrt)SHBG, and (log)FEI but only when these hormone values were modeled independently of (log)FSH values and the specimens were obtained outside the d 2-5 window. When modeled simultaneously with (log)FSH, (log)E2, (sqrt)SHBG, and (log)FEI were no longer significantly associated with symptom prevalence. (Cubic root)T and (sqrt)DHEAS concentrations and (log)FTI were not associated with the prevalence of VMS. CONCLUSIONS: Annual serum FSH concentrations, but not E2, T, DHEAS, FTI, or FEI when collectively modeled longitudinally, are associated with both the prevalence and frequency of VMS in women at midlife.

Adult↗
PubMed2006

Estimating the energy gap among US children: a counterfactual approach.

OBJECTIVE: Our goal was to quantify the magnitude of energy imbalance responsible for the increase in body weight among US children during the periods 1988-1994 and 1999-2002. METHODS: We adopted a counterfactual approach to estimate weight gains in excess of normal growth and the implicit "energy gap"--the daily imbalance between energy intake and expenditure. On the basis of Centers for Disease Control and Prevention growth charts, we constructed weight, height, and BMI percentile distributions for cohorts 2 to 4 and 5 to 7 years of age in the 1988-1994 National Health and Nutrition Examination Survey (N = 5000). Under the counterfactual "normal-growth-only" scenario, we assumed that these percentile distributions remained the same as the cohort aged 10 years. Under this assumption, we projected the weight and height distributions for this cohort at 12 to 14 and 15 to 17 years of age on the basis of their baseline weight-for-age and stature-for-age percentiles. We compared these distributions with those for corresponding age groups in the 1999-2002 National Health and Nutrition Examination Survey (N = 3091) approximately 10 years after the 1988-1994 National Health and Nutrition Examination Survey. We calculated differences between the counterfactual and observed weight distributions and translated this difference into the estimated average energy gap, adjusting for increased total energy expenditure attributable to weight gain. In addition, we estimated the average excess weight accumulated among overweight adolescents in the 1999-2002 National Health and Nutrition Examination Survey, validating our counterfactual assumptions by analyzing longitudinal data from the National Longitudinal Survey of Youth and Bogalusa Heart Study. RESULTS: Compared with the counterfactual scenario, boys and girls who were aged 2 to 7 in the 1988-1994 National Health and Nutrition Examination Survey gained, on average, an excess of 0.43 kg/year over the 10-year period. Assuming that 3500 kcal leads to an average of 1-lb weight gain as fat, our results suggest that a reduction in the energy gap of 110-165 kcal/day could have prevented this increase. Among overweight adolescents aged 12 to 17 in 1999-2002, results indicate an average energy imbalance ranging from 678 to 1017 kcal/day because of an excess of 26.5 kg accumulated over 10 years. CONCLUSIONS: Quantifying the energy imbalance responsible for recent changes in weight distribution among children can provide salient targets for population intervention. Consistent behavioral changes averaging 110 to 165 kcal/day may be sufficient to counterbalance the energy gap. Changes in excess dietary intake (eg, eliminating one sugar-sweetened beverage at 150 kcal per can) may be easier to attain than increases in physical activity levels (eg, a 30-kg boy replacing sitting for 1.9 hours with 1.9 hours walking for an extra 150 kcal). Youth at higher levels of weight gain will likely need changes in multiple behaviors and environments to close the energy gap.

Adolescent↗
PubMed1990

Daydreaming and curiosity: stability and change in gifted children and adolescents.

Developmental differences in daydreaming and curiosity based on cross-sectional data have been reported, but longitudinal data are lacking. Patterns of longitudinal stability and change in two intellectual styles, daydreaming and curiosity, in gifted children and adolescents are described in this paper. Seventy-four intellectually gifted children attended a special program during two consecutive summers. Self-reports of their frequency of and attitudes toward daydreaming and two measures of their curiosity were obtained each year. The findings suggest a pattern of both change and stability in intellectual styles over time. Measures which tap the content of daydreams changed over time, but measures of process or ways of relating to the environment, such as curiosity and frequency of daydreaming, were fairly stable.

Achievement↗