Residential Mobility Across Local Areas in the United States and the Geographic Distribution of the Healthy Population

Determining whether population dynamics provide competing explanations to place effects for observed geographic patterns of population health is critical for understanding health inequality. We focus on the working-age population—the period of adulthood when health disparities are greatest—and analyze detailed data on residential mobility collected for the first time in the 2000 U.S. census. Residential mobility over a five-year period is frequent and selective, with some variation by race and gender. Even so, we found little evidence that mobility biases cross-sectional snapshots of local population health. Areas undergoing large or rapid population growth or decline may be exceptions. Overall, place of residence is an important health indicator; yet, the frequency of residential mobility raises questions of interpretation from etiological or policy perspectives, complicating simple understandings that residential exposures alone explain the association between place and health. Psychosocial stressors related to contingencies of social identity associated with being black, urban, or poor in the United States may also have adverse health impacts that track with structural location even with movement across residential areas.     

A Study of the Determinants and of the Impact of Flexibility on Employee Benefit Satisfaction

The purpose of this study was to examine the influence of individual characteristics and organizational justice on employee benefit satisfaction, and to explore the role of flexible benefit plans. Employees from three Canadian organizations were surveyed. A total of 285 usuable questionnaires were returned, for a response rate of 42%. The variables in the model accounted for more than 40% of the variance in benefit satisfaction. The findings showed that while distributive and procedural justice were useful in predicting benefit satisfaction, the concept of process justice had the greatest effect on satisfaction. Among the variables, communication had the greatest impact. The effect of flexibility, although significant, was ambiguous. Sociodemographic factors had a very limited effect when perceptual variables were introduced into the equation. The paper also sets out the limitations of the study and its practical implications, and makes some suggestions for future research.     

Stability of Maternal Autonomy Support between Infancy and Preschool Age

The goals of this article were to examine (1) the relative and absolute stability of maternal autonomy support between infancy and preschool age, and (2) the moderating role of child gender, maternal attachment state of mind, and stressful life events. Sixty‐nine mother–child dyads participated in five visits when the child was 8, 15, and 18 months, as well as 2 and 3 years. The results suggested that maternal autonomy support is stable in relative terms, but that its mean level decreases over time. Moreover, there was significant relative stability only for mothers of girls, mothers who showed greater coherence of mind with respect to attachment, and mothers who experienced fewer stressful life events. These results speak to the relevance of investigating parent, child, and contextual factors when examining the conditions that promote or hinder stability in parenting behaviors.     

Initiating a Caregiving Relationship: Pregnancy and Childbirth Factors as Predictors of Maternal Sensitivity

The aim of this study was to investigate the relations between pregnancy and childbirth factors and subsequent quality of maternal interactive behavior in a sample of 116 full‐term infants and their mothers. Mothers reported on the conditions of childbirth when infants were 6–8 months of age, and their interactive behavior was observed during a home visit at 12 months. Results showed that mothers who did not report health problems during pregnancy and who had longer pregnancies, shorter hospital stays, natural deliveries, and infants with greater birthweight were found to be more sensitive during interactions with infants at 12 months. All these relations held after accounting for socio‐economic factors and maternal psychological distress, except for the effect of type of delivery. This pattern of results, however, was almost exclusively due to mothers who already had at least one other child. Very few such relations were found among primiparous mothers.     

Building adaptive estimating equations when inverse of covariance estimation is difficult

Summary. To construct an optimal estimating function by weighting a set of score functions, we must either know or estimate consistently the covariance matrix for the individual scores. In problems with high dimensional correlated data the estimated covariance matrix could be unreliable. The smallest eigenvalues of the covariance matrix will be the most important for weighting the estimating equations, but in high dimensions these will be poorly determined. Generalized estimating equations introduced the idea of a working correlation to minimize such problems. However, it can be difficult to specify the working correlation model correctly. We develop an adaptive estimating equation method which requires no working correlation assumptions. This methodology relies on finding a reliable approximation to the inverse of the variance matrix in the quasi-likelihood equations. We apply a multivariate generalization of the conjugate gradient method to find estimating equations that preserve the information well at fixed low dimensions. This approach is particularly useful when the estimator of the covariance matrix is singular or close to singular, or impossible to invert owing to its large size.     

Uncertainty Distribution Associated with Estimating a Proportion in Microbial Risk Assessment

The uncertainty associated with estimates should be taken into account in quantitative risk assessment. Each input's uncertainty can be characterized through a probabilistic distribution for use under Monte Carlo simulations. In this study, the sampling uncertainty associated with estimating a low proportion on the basis of a small sample size was considered. A common application in microbial risk assessment is the estimation of a prevalence, proportion of contaminated food products, on the basis of few tested units. Three Bayesian approaches (based on beta(0, 0), beta(1/2, 1/2), and beta(l, 1)) and one frequentist approach (based on the frequentist confidence distribution) were compared and evaluated on the basis of simulations. For small samples, we demonstrated some differences between the four tested methods. We concluded that the better method depends on the true proportion of contaminated products, which is by definition unknown in common practice. When no prior information is available, we recommend the beta (1/2, 1/2) prior or the confidence distribution. To illustrate the importance of these differences, the four methods were used in an applied example. We performed two-dimensional Monte Carlo simulations to estimate the proportion of cold smoked salmon packs contaminated by Listeria monocytogenes, one dimension representing within-factory uncertainty, modeled by each of the four studied methods, and the other dimension representing variability between companies.     

Disability Status Differentials Among Asian Immigrants in the United States: The Added Dimensions of Duration and Age

The healthy immigrant and erosion effects are widely cited observations for immigrants’ health patterns in the United States. Yet, these effects are not always found in empirical studies. We examined both effects among Asians using the 2000 Census Public Microdata Sample. We examined six disability outcomes: sensory, physical, mental, mobility, work and self-care. We also investigated the moderating effect of age on years in the United States. We found substantial variation in disability status across our 13 Asian ethnic groups. Support for the healthy immigrant and erosion effects differed across the disability outcomes. For physical, sensory and mental disabilities, the healthy immigrant and erosion effects were displayed at younger ages. For work and mobility disabilities, younger immigrants displayed a higher prevalence for these outcomes than their US-born counterparts, but this pattern reversed at older ages. Self-care disability did not show any duration differences. Age also appears to be an important moderator of the healthy immigrant and erosion effects. Cohorts and question wording may also be important alternative explanations to immigrant health patterns.     

Mechanistic Insights Aid the Search for CFC Substitutes: Risk Assessment of HCFC-123 as an Example

An international consensus on the need to reduce the use of chlorofluorocarbons (CFCs) and other ozone-depleting gases such as the halons led to the adoptions of the 1987 Montreal Protocol and Title VI of the 1990 Clean Air Act Amendments, "Protecting Stratospheric Ozone." These agreements included major provisions for reducing and eventually phasing out production and use of CFCs and halons as well as advancing the development of replacement chemicals. Because of the ubiquitous use and benefits of CFCs and halons, an expeditious search for safe replacements to meet the legislative deadlines is of critical importance. Toxicity testing and health risk assessment programs were established to evaluate the health and environmental impact of these replacement chemicals. Development and implementation of these programs as well as the structural-activity relationships significant for the development of the replacement chemicals are described below. A dose-response evaluation for the health risk assessment of the replacement chemical HCFC-123 (2,2-dichloro-1,1,1-trifluoroethane) is also presented to show an innovative use of physiologically based pharmacokinetic (PBPK) modeling. This is based on a parallelogram approach using data on the anesthetic gas halothane, a structural analog to HCFC-123. Halothane and HCFC-123 both form the same metabolite, trifluoroacetic acid (TFA), indicative of the same metabolic oxidative pathway attributed to hepatotoxicity. The parallelogram approach demonstrates the application of template model structures and shows how PBPK modeling, together with judicious experimental design, can be used to improve the accuracy of health risk assessment and to decrease the need for extensive laboratory animal testing.