Biological and environmental determinants of plasma homocysteine

This article gives an overview over common physiological, lifestyle, and pathological conditions that may modulate the homocysteine status. The interplay of several environmental factors, including age, gender, nutrition, smoking, and coffee consumption and physical activity with commonly used drugs and prevalent diseases are described. In most cases, an abnormal homocysteine status is not caused by a single factor alone but often is the result of combined effects. We address these frequently found "clusters" of homocysteine-modulating factors. Finally, we give an overview of likely causes of hyperhomocysteinemia found in an authentic material. This material is based on 2462 routine measurements of plasma total homocysteine carried out at the Haukeland University Hospital. The data represent the total number of combined homocysteine and methylmalonic acid determinations, requested by general practitioners in Norway during February 1998.     

Biological and socioeconomic determinants of child survival

This document describes advances in a conceptual framework under development since 1984 for research on child survival in developing countries. The framework links variables explaining biologically determined disease processes to social determinants in the family and community. The major addition is the extension of previous models of proximate determinants to include fertility-child survival interactions, as well as the interaction between child growth and child survival. The role of health policies within the framework of proximate determinants is also explored. A strategy oriented toward specific diseases will not prove successful in developing countries, where most infant and child deaths are not due to a single cause but rather are the final product of a series of episodes of infection combined with malnutrition. Health policies must therefore identify the risk factors that reduce probabilities of survival as well as the pathologies that actually cause death. Risk factors can be classified as proximate determinants, the basic biological mechanisms that directly influence risks of morbidity and mortality, and underlying determinants, all the other social and environmental determinants that operate indirectly through the proximate determinants to influence infant survival. The 1st step in applying the focus on proximate determinants is to achieve a clear understanding of some measurable biological indicators of health and child survival or of their opposites, illness and death. Abnormal growth has been found to be a sensitive and nonspecific indicator of morbidity in children. Measurement of height and weight could serve as the social science counterpart of mortality measurement for a demographer. Mortality and permanent growth stunting are both indicators reflecting different points of chronic and irreversible physical deterioration on the continuum that ranges from good health to death. The proposed conceptual framework integrates Bongaarts' proximate fertility determinants with the proximate child survival determinants proposed in an earlier work by Mosley and Chen. 9 specific determinants are divided into 4 categories of factors that influence both child survival and fertility: factors regulating exposure to conception (sexual union, coital frequency), lactation, ecological risk (dietary deficiency, environmental contamination, accidents), and direct interventions (personal preventive measures, curative measures, and intentionally inflicted lesions). 5 groups of underlying determinants operate through the proximate determinants: individual factors, family factors, cultural factors, institutional factors, and environmental factors.     

Prevention of low birth weight

Low birth weight is a powerful predictor of infant mortality. Programs to prevent low birth weight must be based on detailed knowledge of its risk factors, but thus far the search for indicators of risk has not led to an overall strategy that permits prevention of low birth weight. Published works have emphasized some aspects of risk but have neglected study of the interrelations between different risk factors. Moreover, the most satisfactory indicators have not always been selected to represent the diverse processes involved. Research on risks associated with health services and nutrition exemplify these difficulties. For the study of low birth weight, research on health services has centered on prenatal surveillance, with the gestational age at the 1st visit or the number of visits the most frequent indicators. Prenatal care is studied by researchers because it is associated with other factors affecting the fetus through inadequate diet, such as poverty, stress, alcoholism, or smoking. These studies postulate that changes in the quality and amount of prenatal care will be associated with a decline in prevalence of low birth weight, independent of the conditions associated with inattendance at obstetric consultations. Indicators of prenatal surveillance have predictive value with respect to the probability of low birth weight, can be expressed numerically through the number of visits and gestational age at initiation, and can be obtained by auxiliary personnel. But they are inadequate indicators because the populations obtaining good prenatal care are biased by self-selection. Moreover, prenatal surveillance is considered primarily as an instrument of detection which does not necessarily lead to action in subjects at risk. Most nutritionally-focussed research on low birth weight has centered on energy reserves in studies conducted among populations in which malnutrition is common. The most frequently used indicators involve indirect evaluation of body composition. Energy reserves have predictive value for birth weight, can be expressed numerically, and are directly related to the weight of the infant so that modifications in the magnitude of the reserves are positively associated with a reduction in prevalence of low birth weight. Information on energy reserves can be collected by auxiliary personnel without costly equipment. Energy reserves have greater predictive value in malnourished populations and there is a threshold above which the association is lost. Although energy reserves are susceptible to modification, they are rarely tied directly to preventive or therapeutic actions. The adequacy of other risk factors as indicators to be used in programs to prevent low birth weight should be systematically assessed in a similar manner. A start is made in an annex to this work which summarizes the rationale for examining the social, family, and biological variables believed to be the most relevant.     

Low birth weight and blood pressure

Evidence supporting the association of normal and pathologically elevated blood pressure with low birth weight is presented and discussed in this article because of the overwhelming global prevalence of hypertension and its impact on individuals and nations. The findings provide strong impetus for the medical and public health communities to consider the concept of the "developmental origins of health and disease" in developing approaches to address the growing burden of hypertension worldwide.     

Adolescence and the social determinants of health

The health of adolescents is strongly affected by social factors at personal, family, community, and national levels. Nations present young people with structures of opportunity as they grow up. Since health and health behaviours correspond strongly from adolescence into adult life, the way that these social determinants affect adolescent health are crucial to the health of the whole population and the economic development of nations. During adolescence, developmental effects related to puberty and brain development lead to new sets of behaviours and capacities that enable transitions in family, peer, and educational domains, and in health behaviours. These transitions modify childhood trajectories towards health and wellbeing and are modified by economic and social factors within countries, leading to inequalities. We review existing data on the effects of social determinants on health in adolescence, and present findings from country-level ecological analyses on the health of young people aged 10-24 years. The strongest determinants of adolescent health worldwide are structural factors such as national wealth, income inequality, and access to education. Furthermore, safe and supportive families, safe and supportive schools, together with positive and supportive peers are crucial to helping young people develop to their full potential and attain the best health in the transition to adulthood. Improving adolescent health worldwide requires improving young people's daily life with families and peers and in schools, addressing risk and protective factors in the social environment at a population level, and focusing on factors that are protective across various health outcomes. The most effective interventions are probably structural changes to improve access to education and employment for young people and to reduce the risk of transport-related injury.     

Biological determinants of spontaneous physical activity

A decline in daily physical activity levels is clearly a major factor contributing to the current obesity epidemic affecting both developed and developing countries in the world. This escalating problem is associated with increased morbidity and mortality and reduced psychosocial health. Thus, increasing physical activity has become the strategy of choice in public health strategies to prevent obesity. Efforts to improve levels of physical activity in the population rely upon an accurate understanding of the determinants of physical activity. Most research has focused on environmental and social influences, while the potential for physical activity to be controlled by intrinsic biological processes has been largely overlooked. This review presents some of the compelling and diverse evidence that has emerged recently showing that physical activity energy expenditure is a critical factor in both the successful regulation of energy balance in normal individuals, as well as the abnormal regulation of energy balance that characterizes obesity. Although the metabolic and genetic factors involved in these regulatory processes remain mostly unidentified, some novel discoveries have been made in this area recently and these are described within this review.     

Variation of serum ferritin in low birth weight infants with maternal ferritin, birth weight and gestational age.

Serum ferritin measured at birth in 69 low birth weight infants proved to vary with gestational age as well as with weight. The increase with gestational age was even more striking when the infants small for gestational age were excluded. The relation between maternal and infant serum ferritin concentration was investigated for 2 groups of infants and their mothers (*preterm and term infants, respectively). Neither in preterm nor in term infants was the serum ferritin found to vary with that in the respective mothers.     

Preterm birth, low birth weight, and risk for esophageal adenocarcinoma

BACKGROUND & AIMS: Gastroesophageal reflux is common among preterm infants and those who are small for gestational age, and it is a strong risk factor for adenocarcinoma of the esophagus. METHODS: In a cohort of 3364 individuals born preterm and/or small for gestational age between 1925 and 1949, we assessed the long-term risk for esophageal cancer. RESULTS: The standardized incidence rate ratio for esophageal adenocarcinoma was increased more than 7-fold in the cohort (standardized incidence rate ratio, 7.27; 95% confidence interval, 1.98-18.62), and a birth weight <2000 g was associated with a more than 11-fold increase in risk (standardized incidence rate ratio, 11.5; 95% confidence interval, 1.39-41.5). CONCLUSIONS: The associations may be spurious, but if not, they may be explained by increased gastroesophageal reflux during infancy among infants born preterm and/or small for gestational age.     

Cardiac catheterization of low birth weight infants

The increased survival of low birth weight infants means that more of these infants may be candidates for catheter interventions. There are few data on the results of cardiac catheterization in this group. This study aimed to analyze, retrospectively, cardiac catheterization of infants weighing ≤2.5 kg, with emphasis on the results of interventions. The complication rates of interventional and diagnostic procedures were compared. One hundred eleven catheterizations were performed in 107 patients between 1985 and 1998. Thirty-one procedures were interventional. Balloon atrial septostomy (n = 16), balloon pulmonary valvuloplasty (n = 10), balloon pulmonary angioplasty (n = 1), and coil occlusion of collateral vessels (n = 3) were all performed successfully. One infant (3%) died while undergoing myocardial biopsy. The reintervention rate for isolated pulmonary valve stenosis was 25% (2 of 8) at 1 month, 57% (4 of 7) at 6 months, and 71% (5 of 7) at 1 year. Complications were significantly more frequent during interventional (13 of 31, 42%) than during diagnostic (13 of 80, 16%) procedures. The most common complications during interventions were arrhythmias (3 of 31, 10%) and respiratory deterioration (3 of 31, 10%). Cardiac catheterization was technically feasible in all patients. Balloon pulmonary valvuloplasty and atrial septostomy provided good palliation in this patient group. The mortality of interventional procedures was low. The high incidence of respiratory complications suggests that low birth weight infants should undergo elective ventilation for interventional cardiac catheterization.