OBJECTIVES: This study investigated the independent and relative effects of family structure, race, and poverty on the health of US children and youth under 20 years of age at two time periods, 1978 through 1980 and 1989 through 1991. METHODS: Data were from the National Health Interview Surveys. Multivariate logit regression methods were used to analyze the effects of family structure, poverty, and race on children's health. RESULTS: Children in families headed by single mothers, Black children, and those living below 150% of the poverty index were much more likely to be in poor or fair health than children in two-parent families, White children, or those in more affluent families. Poverty had the strongest effect on child health in both time periods. CONCLUSIONS: The association between children's health and living below 150% of the poverty index is not explained by race or family structure. The disparity in child health by family income has serious consequences for both the child and society.
An understanding of the complexity of the cardiovascular system is incomplete without a knowledge of the venous system. It is important for students to understand that, in a closed system, like the circulatory system, changes to the venous side of the circulation have a knock-on effect on heart function and the arterial system and vice versa. Veins are capacitance vessels feeding blood to the right side of the heart. Changes in venous compliance have large effects on the volume of blood entering the heart and hence cardiac output by the Frank-Starling Law. In healthy steady-state conditions, venous return has to equal cardiac output, i.e., the heart cannot pump more blood than is delivered to it. A sound understanding of the venous system is essential in understanding how changes in cardiac output occur with changes in right atrial pressure or central venous pressure, and the effect these changes have on arterial blood pressure regulation. The aim of this paper is to detail simple hands-on physiological assessments that can be easily undertaken in the practical laboratory setting and that illustrate some key functions of veins. Specifically, we illustrate that venous valves prevent the backflow of blood, that venous blood pressure increases from the heart to the feet, that the skeletal muscle pump facilitates venous return, and we investigate the physiological and clinical significance of central venous pressure and how it may be assessed.
Intestinal smooth muscle contracts rhythmically in the absence of nerve and hormonal stimulation because of the activity of pacemaker cells between and within the muscle layers. This means that the autonomic nervous system modifies rather than initiates intestinal contractions. The practical described here gives students an opportunity to observe this spontaneous activity and its modification by agents associated with parasympathetic and sympathetic nerve activity. A section of the rabbit small intestine is suspended in an organ bath, and the use of a pressure transducer and data-acquisition software allows the measurement of tension generated by the smooth muscle of intestinal walls. The application of the parasympathetic neurotransmitter ACh at varying concentrations allows students to observe an increase in intestinal smooth muscle tone with increasing concentrations of this muscarinic receptor agonist. Construction of a concentration-effect curve allows students to calculate an EC50 value for ACh and consider some basic concepts surrounding receptor occupancy and activation. Application of the hormone epinephrine to the precontracted intestine allows students to observe the inhibitory effects associated with sympathetic nerve activation. Introduction of the drug atropine to the preparation before a maximal concentration of ACh is applied allows students to observe the inhibitory effect of a competitive antagonist on the physiological response to a receptor agonist. The final experiment involves the observation of the depolarizing effect of K(+) on smooth muscle. Students are also invited to consider why the drugs atropine, codeine, loperamide, and botulinum toxin have medicinal uses in the management of gastrointestinal problems.
Much of the epidemiologic research in the United States has been based only on the categories of age, sex and race; thus, race has often been used in health statistics as a surrogate for social and economic disadvantage. Few multivariate analyses distinguish effects of components of social class (such as economic level) from the relative, joint, and independent effects of sociocultural identifiers such as race or ethnicity. This paper reviews studies of social class and minority status differentials in health, with a particular emphasis on health status outcomes which are known or suspected to be related to environmental quality and conditions which increase susceptibility to environmental pollutants. Sociodemographic data are presented for the U.S. population, including blacks, Asian American/Pacific Islanders, American Indian/Alaska Natives, and Hispanics. Four areas of health status data are addressed: mortality, health of women of reproductive age, infant and child health, and adult morbidity. Conceptual and methodological issues surrounding various measures of position in the system of social strata are discussed, including the multidimensionality of social class, in the context of the importance of these issues to public health research. Whenever possible, multivariate studies that consider the role of socioeconomic status in explaining racial/ethnic disparities are discussed.
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