Social Determinants of the Health of Urban Populations: Methodologic Considerations

A full understanding of the role of the urban environment in shaping the health of populations requires consideration of different features of the urban environment that may influence population health. The social environment is key to understanding the way in which cities affect the health of populations. Social determinants of health (SDH) are important, generally, yet can have different effects in different settings from urban to rural, between countries, between cities, and within cities. Failure to acknowledge, and more importantly, to understand the role of SDH in health and access to health and social services will hamper any effort to improve the health of the population. In this paper, we will briefly summarize a few key SDH and their measurement. We will also consider methodologic tools and some methodologic challenges. The concepts presented here are broadly applicable to a variety of settings: developed and developing countries, slum areas, inner cities, middle income neighborhoods, and even higher income neighborhoods. However, our focus will be on some of the more vulnerable urban populations who are most profoundly affected by SDH.     

Geographical display of health information: study of hepatitis C infection in Karachi, Pakistan

The prevalence of hepatitis C and other infections is increasing in urban areas of developing countries. Data on such diseases are often limited to facility-based information. However, even this is not available in a usable form to health care providers, health managers and policy makers. We present a simple technique for visually displaying facility based prevalence information on hepatitis C using basic geographic information system (GIS) techniques. We display the prevalence of hepatitis C for the city of Karachi, Pakistan for the first time. The distribution tends to indicate that there are areas of higher prevalence located in specific districts. There is also a trend of higher prevalence in less affluent urban areas. Such simple applications of mapping technology are useful for rapidly summarizing and displaying information in a contextually and spatially meaningful fashion, and its use should be encouraged for displaying health indicators in developing countries.     

Estimates for cervical abnormalities in Vanuatu

OBJECTIVE: To use the Pap smear to establish a recent prevalence of cervical abnormalities within a select population in Vanuatu, a developing country. METHODS: Cervical smears (n=907) were collected from Ni-Vanuatu women from both urban and rural islands within Vanuatu between August 2001 and September 2005. RESULTS: The prevalence of low-grade epithelial abnormalities for the total population was 2.9% and the prevalence of the high-grade epithelial abnormalities/cancer was 2.0%. There was a significant difference (p<0.05) in prevalence of high-grade epithelial abnormalities/cancer between the urban and rural populations sampled, with a higher prevalence in the urban population. CONCLUSIONS: The prevalence of pre-cancer and cancer in Vanuatu is high compared with Victorian (Australian) statistics yet comparable with other developing countries with no cervical screening programs available. IMPLICATIONS: This study will hopefully assist in future planning of women's health programs and relevant preventive strategies to combat cervical cancer in Vanuatu.     

Urban Health Inequities and the Added Pressure of Climate Change: An Action-Oriented Research Agenda

Climate change will likely exacerbate already existing urban social inequities and health risks, thereby exacerbating existing urban health inequities. Cities in low- and middle-income countries are particularly vulnerable. Urbanization is both a cause of and potential solution to global climate change. Most population growth in the foreseeable future will occur in urban areas primarily in developing countries. How this growth is managed has enormous implications for climate change given the increasing concentration and magnitude of economic production in urban localities, as well as the higher consumption practices of urbanites, especially the middle classes, compared to rural populations. There is still much to learn about the extent to which climate change affects urban health equity and what can be done effectively in different socio-political and socio-economic contexts to improve the health of urban dwelling humans and the environment. But it is clear that equity-oriented climate change adaptation means attention to the social conditions in which urban populations live—this is not just a climate change policy issue, it requires inter-sectoral action. Policies and programs in urban planning and design, workplace health and safety, and urban agriculture can help mitigate further climate change and adapt to existing climate change. If done well, these will also be good for urban health equity.     

Strategies to improve immunization services in urban Africa

The urban poor constitute a rapidly increasing proportion of the population in developing countries. Focusing attention on underserved urban slums and squatter settlements will contribute greatly to immunization programme goals, because these areas account for 30-50% of urban populations, usually provide low access to health services, carry a large burden of disease mortality, and act as sources of infection for the city and surrounding rural areas. Improvement of urban immunization programmes requires intersectorial collaboration, use of all opportunities to vaccinate eligible children and mothers, identification of low-coverage neighbourhoods and execution of extra activities in these neighbourhoods, and community mobilization to identify and refer persons for vaccination. Improved disease surveillance helps to identify high-risk populations and document programme impact. New developments in vaccines, such as the high-dose Edmonston-Zagreb vaccine, will allow changes in the immunization schedule that facilitate the control of specific diseases. Finally, operational research can assist managers to conduct urban situation assessments, evaluate programme performance at the "micro" level, and design and monitor interventions.     

Bringing Sexual and Reproductive Health in the Urban Contexts to the Forefront of the Development Agenda: The Case for Prioritizing the Urban Poor

Estimates suggest that over 90 % of population increase in the least developed countries over the next four decades will occur in urban areas. These increases will be driven both by natural population growth and rural–urban migration. Moreover, despite its status as the world’s least urbanized region, the urban population in the sub-Saharan Africa region is projected to increase from under 40 % currently to over 60 % by 2050. Currently, approximately 70 % of all urban residents in the region live in slums or slum-like conditions. Sexual and reproductive health (SRH) risks for the urban poor are severe and include high rates of unwanted pregnancies, sexually transmitted infections, and poor maternal and child health outcomes. However, the links between poverty, urbanization, and reproductive health priorities are still not a major focus in the broader development agenda. Building on theoretical and empirical data, we show that SRH in urban contexts is critical to the development of healthy productive urban populations and, ultimately, the improvement of quality of life. We posit that a strategic focus on the sexual and reproductive health of urban residents will enable developing country governments achieve international goals and national targets by reducing health risks among a large and rapidly growing segment of the population. To that end, we identify key research, policy and program recommendations and strategies required for bringing sexual and reproductive health in urban contexts to the forefront of the development agenda.     

Epidemiology of epilepsy in developing countries.

Epilepsy is an important health problem in developing countries, where its prevalence can be up to 57 per 1000 population. This article reviews the epidemiology of epilepsy in developing countries in terms of its incidence, prevalence, seizure type, mortality data, and etiological factors. The prevalence of epilepsy is particularly high in Latin America and in several African countries, notably Liberia, Nigeria, and the United Republic of Tanzania. Parasitic infections, particularly neurocysticercosis, are important etiological factors for epilepsy in many of these countries. Other reasons for the high prevalence include intracranial infections of bacterial or viral origin, perinatal brain damage, head injuries, toxic agents, and hereditary factors. Many of these factors are, however, preventable or modifiable, and the introduction of appropriate measures to achieve this could lead to a substantial decrease in the incidence of epilepsy in developing countries.     

Parasitic food-borne and water-borne zoonoses

Estimates suggest that almost half of the population of the world is affected by water-borne and food-borne infections. Parasitic food-borne and water-borne zoonoses contribute to this statistic by inflicting a heavy toll on human health and causing serious direct and indirect losses to the agricultural industry. The inability of non-industrialised countries to keep pace with population growth, migration from rural to urban areas and the demand for clean, safe drinking water and proper sanitation means that water-borne zoonoses will continue to exact an increasing burden of ill health in these countries. The consumption of raw or undercooked meat, crustaceans, and fresh-water fish and vegetables facilitates transmission of large numbers of zoonotic infections. The burgeoning tourist industry, emigration and the importation of food from endemic regions has resulted in increasing diagnosis of these infections in non-endemic countries. The authors examine the epidemiology, medical and veterinary public health importance and recent developments in diagnosis, treatment and control of the most important parasitic food-borne and water-borne infections.     

HIV, syphilis, and hepatitis B and C prevalence among patients with mental illness: a review of the literature

A limited number of studies worldwide have investigated the prevalence of HIV, syphilis, and hepatitis B and C infection among psychiatric patients. However, prevalence of these infections in the population with chronic mental illness has not been clearly established. Most of the published papers are from developed countries and have derived from relatively small and non-representative samples. We performed a systematic review of the published literature to identify studies on these infectious diseases within psychiatric populations in Brazil and other developing countries. Overall, prevalence rates varied from 0% to 29% for HIV; 1.6% to 66% for HBV; 0.4% to 38% for HCV; and 1.1% to 7.6% for syphilis. Several risk factors were identified and discussed, although sampling limitations restrict the generalization of study findings. This review highlights the lack of information on the prevalence of sexually transmitted diseases and their associated factors among persons with chronic mental illness and identifies gaps in the knowledge base in both developing and developed countries.     

Pandemic Influenza as 21st Century Urban Public Health Crisis

The percentage of the world’s population living in urban areas will increase from 50% in 2008 to 70% (4.9 billion) in 2025. Crowded urban areas in developing and industrialized countries are uniquely vulnerable to public health crises and face daunting challenges in surveillance, response, and public communication. The revised International Health Regulations require all countries to have core surveillance and response capacity by 2012. Innovative approaches are needed because traditional local-level strategies may not be easily scalable upward to meet the needs of huge, densely populated cities, especially in developing countries. The responses of Mexico City and New York City to the initial appearance of influenza A pandemic (H1N1) 2009 virus during spring 2009 illustrate some of the new challenges and creative response strategies that will increasingly be needed in cities worldwide.     

Urbanisation: the implications for health

This article draws attention to the health implications of poverty in urban areas of developing countries. Migrants in Africa are depicted as bringing poverty with them and, in turn, being exposed to urban problems of access to water, sanitation, and shelter. Urban populations in low-income countries are viewed as carrying a double burden of health problems from communicable diseases and health problems typically associated with economically advanced societies, such as chronic diseases, accidents, and violence. Disease rates among children in urban slums from infectious diseases are reported to be sometimes higher than in rural areas. The rates of heart diseases and neoplasms are higher among the urban poor, even in Southern countries. The double burden is not shared equally by cities. The European experience is described as one where health professionals were instrumental in shifting policies to alleviating poor health conditions by changing physical conditions and socioeconomic conditions and improving the adjustment to the stresses of urban living. The European experience needs to be applied and is being applied by health professionals working in African cities. Urbanization is expected to increase by 40-66% by the year 2010. Shifts will occur due to the desire for better jobs and better lives and due to displacement from war and civil conflict. 30-60% of urban population already live in slums, which may have a lack of access to basic needs such water, sanitation, and adequate housing, or inadequate food supplies and expensive and scarce fuel. Slums are characterized by high population densities and location on hazardous sites. Children are at high risk.     

Shifting obesity trends in Brazil

OBJECTIVE: To describe secular trends in obesity in various settings and socio-economic groups of the adult population of Brazil. METHODS: Trend analysis of the prevalence of obesity in adults aged over 20 y (body mass index >/=30.0 kg/m2) applied to anthropometric and socio-economic data collected by three comparable household surveys undertaken in the two most populated Brazilian regions in 1975 (n=95,062), 1989 (n=15,585) and 1997 (n=10,680). RESULTS: While previous trends (1975-1989) showed increasing obesity prevalence for all population groups except for men in rural areas, recent trends (1989-1997) have pointed to a much more complex picture where increases in obesity tend to be more intense in men than in women, in rural than in urban settings and in poorer than in richer families. Particularly notable was the fact that, in the recent period, obesity was actually reduced for women belonging to the upper income groups, especially in urban settings. CONCLUSION: Earlier obesity trends in Brazil entirely agree with what has been described for both developed and developing countries where reliable secular trend information exists, but the 1989-1997 trend of a substantial reduction in the prevalence of obesity among upper income urban women (12.8-9.2%, or a 28% reduction), is unique in a developing country and, indeed, up to now has only been detected in Scandinavian populations. It is speculated that this declining obesity trend may be a result of an intense mass media work focused on combating a sedentary life style and promoting better food habits.     

我国中年人群超重率和肥胖率的现状及发展趋势

目的：了解我国中年人群超重率和肥胖率现状，定量估价近十余年来超重率和肥胖率发展趋势。方法：选择城乡不同地区、不同职业的15个人群（每个人群1000人左右，男女各半，年龄35－59岁）共计15389人为调查对象，以BMI≥25为超重，BMI≥30为肥胖，分别计算超重率和肥胖率，并与20世纪80年代初和90年代初可比资料比较。结果：①各地人群超重率和肥胖率存在极大差异。在超重严重的地区，中年人群超重率已超过50％；②一般来说这种人群差别表现为：北方高于南方，中城市高于内地农村，女性高于男性；③中年人群的超重目前尚主要表现为“肥胖前期”，肥胖率在绝大多数人群中低于10％；④与80年代初相比，90年代初各人群超重率和肥胖率均上升；与90年代初相比，90年代末多数人群超重率肥胖率均再次 大幅度上升。结论：对我国人群超重和肥胖的干预迫在眉睫。     

Urbanization and health in developing countries

In developing countries the level of urbanization is expected to increase to 39.5% by the end of this century and to 56.9% by 2025. The number of people living in slums and shanty towns represent about one-third of the people living in cities in developing countries. This article focuses upon these poor urban populations and comments upon their lifestyle and their exposure to hazardous environmental conditions which are associated with particular patterns of morbidity and mortality. The concept of marginality has been used to describe the lifestyle of the urban poor in developing countries. This concept is critically examined and it is argued that any concept of the urban poor in developing countries being socially, economically or politically marginal is a myth. However, it can certainly be claimed that in health terms the urban poor are marginal as demonstrated by some of the studies reviewed in this article. Most studies of the health of the urban poor in developing countries concentrate on the environmental conditions in which they live. The environmental conditions of the urban poor are one of the main hazards of the lifestyle of poor urban residents. However, other aspects of their way of life, or lifestyle, have implications for their health. Issues such as smoking, diet, alcohol and drug abuse, and exposure to occupational hazards, have received much less attention in the literature and there is an urgent need for more research in these areas.     

Maternal immunisation in developing countries

Maternal immunisation could help to prevent the 2-3 million neonatal and early infant deaths that occur in the developing world each year. Determining the causes of neonatal and early infant deaths in developing countries is difficult as most occur at home. However, it is likely that at least half are due to infections, several of which might be prevented by maternal immunisation. Even in poor countries with few health facilities, a high percentage of pregnant women attend an antenatal clinic at least once during pregnancy. Thus, an effective delivery system for maternal immunisation already exists and, because of the success of maternal tetanus immunisation, this approach to the prevention of serious illness or death in young infants is widely accepted by the general population. However, the high prevalence of HIV and malaria found in pregnant women in some parts of the developing world, especially sub-Saharan Africa, could have an effect on the efficacy of maternal immunisation as both of these infections adversely affect placental function. Nevertheless, the potential of maternal immunisation to prevent early infant deaths in developing countries needs to be fully explored. The incidence of pneumococcal infections is high in many developing countries and about 25% of these infections occur at an age before protection could be anticipated following vaccination with a pneumococcal conjugate vaccine in infancy. Thus, a strong case can be made for a trial of the effectiveness of maternal immunisation with a pneumococcal vaccine in preventing serious illness or death in young infants in developing countries.     

Diphtheria in North America.

The incidence of diphtheria has declined in North America during the last fifty years until it is now an uncommon disease. This general pattern is similar to that seen in other developed countries with well-organized immunization programmes, but certain noteworthy characteristics have been observed in recent years: foci of infection lingered in two population groups of low socio-economic status, in both of which the skin has been an important reservoir. In central areas of certain cities, endemic diphtheria, chiefly cutaneous, has occurred amongst indigent adult males living in unhygienic conditions; and in the native Indian population of Northern Canada diphtheria infection has been endemic in infants and children, many of the infections being of the skin or ear and toxic disease being uncommon. During the last few years, diphtheria outbreaks have not been reported in urban areas and possibly endemicity is now restricted to northern native populations. The number of infections detected in these northern endemic areas is steadily decreasing.     

Diphtheria in North America

The incidence of diphtheria has declined in North America during the last fifty years until it is now an uncommon disease. This general pattern is similar to that seen in other developed countries with well-organized immunization programmes, but certain noteworthy characteristics have been observed in recent years: foci of infection lingered in two population groups of low socio-economic status, in both of which the skin has been an important reservoir. In central areas of certain cities, endemic diphtheria, chiefly cutaneous, has occurred amongst indigent adult males living in unhygienic conditions; and in the native Indian population of Northern Canada diphtheria infection has been endemic in infants and children, many of the infections being of the skin or ear and toxic disease being uncommon. During the last few years, diphtheria outbreaks have not been reported in urban areas and possibly endemicity is now restricted to northern native populations. The number of infections detected in these northern endemic areas is steadily decreasing.     

Prevalence of markers of hepatitis B virus infection in various countries: a WHO Collaborative Study

A WHO collaborative study on viral hepatitis B in which 21 laboratories in 20 countries participated is described. The aim of the study was to define the prevalence of hepatitis B surface antigen (HBsAg), its subtypes, and its antibody (anti-HBs) by age and sex and urban or rural residence in normal populations in different parts of the world. High-risk groups in the populations and patients with various diseases were also investigated. The results of the study confirmed that HBsAg and anti-HBs prevalence rates were higher in African and Asian countries than in the Americas, Australia, and northern and central Europe. Some eastern and southern European countries, however, were also shown to have high HBsAg and anti-HBs prevalence rates, comparable with those in Africa and Asia. In countries with low HBsAg and anti-HBs prevalence, there seems to be a gradual build-up during late childhood or early adolescence, whereas in countries with high HBsAg and its antibody prevalence, they were frequently detected in preschool children. Although the trend was towards a higher frequency of HBsAg and anti-HBs in urban than in rural and in male than in female populations, the differences were in most cases not significant. On the other hand, a significantly higher prevalence of markers of hepatitis B virus infection was seen in high-risk population groups than in normal populations. This was, however, clearly defined only in areas with low HBsAg and anti-HBs prevalence in the normal population. The geographical distribution of HBsAg subtypes showed a higher prevalence of the ad subdeterminant over ay in central European countries, whereas in eastern and southern Europe the ay subtype predominated. In West Africa, ayw was the only variant found, whereas in East Africa ad occurred more frequently than ay. In Australia, both adw and ayw subtypes were detected, whereas in the Far East and South-east Asia only adw and adr were seen.     

贫穷与疾病

多年来人们就注意到贫穷与疾病有关,即在贫穷落后的国家或地区传染病发病率高。在移民、流动人口等弱势人群中患病率高,农村传染病发病率高于城区。寄生虫病、病毒性疾病、细菌性疾病也是贫穷病,主要流行于发展中国家,与发展中国家缺乏卫生设施、经济落后、住房简陋、收入和受教育程度低、环境卫生差等条件密切相关。贫病相连,因病致贫、返贫是发展中国家面临的严峻挑战。揭示贫穷与疾病的关系有助于职能部门采取有效对策来控制疾病和消除贫困。