Structural Determinants of Infant Mortality in Metropolitan and Nonmetropolitan America1

Abstract A conceptual model of the impact of structural advantage and disadvantage on infant mortality rates is developed and fitted to countylevel data. This model includes mediating endogenous constructs representing medical care availability, the incidence of teenage childbearing, and low birthweight rates and is estimated for three residence categories. Both direct and indirect effects of social structure and teenage childbearing on infant mortality vary significantly across the categories. Structural advantage exerts a significant and negative direct effect on infant mortality rates in urban areas, but in rural areas this effect is indirect, operating through teenage childbearing and low birthweight. Structural disadvantage significantly increases infant mortality in both rural and urban settings, but the effects operate directly in metropolitan areas and indirectly in rural areas. These results underscore the central role that social structure continues to play in determining infant mortality rates in the United States.     

A general systems approach to the patient, hospital staff, family, and community: implications for health care services

This article concerns the application of a general systems concept to the health care system. A system consists of a set of interacting components which are interrelated and interdependent, and function as a unit. In order to identify some of the significant influences on the patient who has been hospitalized, this general systems concept has been applied to health care systems at a number of open systems levels in which he or she participates. These are the body-mind system of the patient (an organism); the patient-hospital staff system (an organization); the system relating the patient to his or her family (a group); and the patient-community system. Analyses of the strategic parts of these systems, their mutual dependencies and the processes which link them, together with their functions, have implications for both hospital-based health-care professionals and hospital administrators. These analyses are generalizable across these four levels of systems. Their implications have importance for health care services.     

Estimation of larval feeding rates using normal linear models involving censored and truncated observations

Experiments to estimate the feeding rates of aquatic insect larvae involved destructive sampling of larvae to determine the position of an introduced food marker as it passed through their guts. A normal linear model involving censoring (equal to complete passage) and truncation is fitted to the measurement of the passage of food. A method for maximum likelihood estimation is derived together with the second order variance-covariance equations. Methods for estimating the effect of larval size on feeding rate are examined.     

Reducing attrition in physical activity programs for older adults

This study investigated attrition in a 6-month physical activity intervention for older adults. The program was based on the social-cognitive theory incorporating self-efficacy factors. Two hundred forty-eight insufficiently active 65- to 74-year-olds were recruited from the Australian federal electoral roll. The intervention comprised walking and strength and flexibility exercises and was conducted in 30 local neighborhoods where the participants resided. Characteristics of individuals lost to attrition (n = 86, 35%) were compared with those of program completers (n = 162, 65%). Logistic-regression analysis showed that those lost to attrition came from areas of lower socioeconomic status, were overweight and less physically active, and had lower walking self-efficacy scores and higher loneliness scores. The results suggest that early assessment of these characteristics should be undertaken to identify individuals at risk of attrition, to improve retention, and to avoid potential bias.     

Introduction to Special Issue: Restoring the Florida Everglades—Balancing Population and the Environment

Population and Environment -