Cities are the predominant mode of living, and the growth in cities is related to the expansion of areas that have concentrated disadvantage. The foreseeable trend is for rising inequities across a wide range of social and health dimensions. Although qualitatively different, this trend exists in both the developed and developing worlds. Improving the health of people in slums will require new analytic frameworks. The social-determinants approach emphasizes the role of factors that operate at multiple levels, including global, national, municipal, and neighborhood levels, in shaping health. This approach suggests that improving living conditions in such arenas as housing, employment, education, equality, quality of living environment, social support, and health services is central to improving the health of urban populations. While social determinant and multilevel perspectives are not uniquely urban, they are transformed when viewed through the characteristics of cities such as size, density, diversity, and complexity. Ameliorating the immediate living conditions in the cities in which people live offers the greatest promise for reducing morbidity, mortality, and disparities in health and for improving quality of life and well being.

Vouchers increased uptake of services and, in some cases, improved service quality and reach to specific groups. Nevertheless, robust evaluation designs are required to measure efficiency.

For 18 months in 2009-2010, the Rockefeller Foundation provided support to establish the Roundtable on Urban Living Environment Research (RULER). Composed of leading experts in population health measurement from a variety of disciplines, sectors, and continents, RULER met for the purpose of reviewing existing methods of measurement for urban health in the context of recent reports from UN agencies on health inequities in urban settings. The audience for this report was identified as international, national, and local governing bodies; civil society; and donor agencies. The goal of the report was to identify gaps in measurement that must be filled in order to assess and evaluate population health in urban settings, especially in informal settlements (or slums) in low- and middle-income countries. Care must be taken to integrate recommendations with existing platforms (e.g., Health Metrics Network, the Institute for Health Metrics and Evaluation) that could incorporate, mature, and sustain efforts to address these gaps and promote effective data for healthy urban management. RULER noted that these existing platforms focus primarily on health outcomes and systems, mainly at the national level. Although substantial reviews of health outcomes and health service measures had been conducted elsewhere, such reviews covered these in an aggregate and perhaps misleading way. For example, some spatial aspects of health inequities, such as those pointed to in the 2008 report from the WHO's Commission on the Social Determinants of Health, received limited attention. If RULER were to focus on health inequities in the urban environment, access to disaggregated data was a priority. RULER observed that some urban health metrics were already available, if not always appreciated and utilized in ongoing efforts (e.g., census data with granular data on households, water, and sanitation but with little attention paid to the spatial dimensions of these data). Other less obvious elements had not exploited the gains realized in spatial measurement technology and techniques (e.g., defining geographic and social urban informal settlement boundaries, classification of population-based amenities and hazards, and innovative spatial measurement of local governance for health). In summary, the RULER team identified three major areas for enhancing measurement to motivate action for urban health-namely, disaggregation of geographic areas for intra-urban risk assessment and action, measures for both social environment and governance, and measures for a better understanding of the implications of the physical (e.g., climate) and built environment for health. The challenge of addressing these elements in resource-poor settings was acknowledged, as was the intensely political nature of urban health metrics. The RULER team went further to identify existing global health metrics structures that could serve as platforms for more granular metrics specific for urban settings.

In the coming decades, the global population will urbanize and age at high rates. Today, half of the world's populations lives in cities. 1 By 2030, that proportion will rise to 60%, and urbanization will occur most greatly in developing countries. 1 At the same time, the world's population aged 60 and over will double from 11% to 22% by 2050, 2 and that growth will be concentrated in urban areas in less developed countries. 3 All of these trends challenge public health workers, doctors, researchers, and urban planners to ensure healthy livable cities for older people.In response to those trends, the WHO has released a guide, Global Age-Friendly Cities, aimed at urban planners, that details the features of age friendly cities: transportation, housing, social participation, respect and social inclusion, civic participation and employment, communication and information, community support and health services, and outdoor spaces and buildings. 1,4 In developing the guide, the WHO conducted 158 focus groups with people aged 60 and over in 35 international cities to determine the age-friendly features of their city, the problems they encounter, and what is missing in the city that could potentially benefit the health or quality of life of the aging population. In addition, the WHO hosted focus groups with a number of caregivers and service providers to complement the information provided by older people. The guide concludes that age-friendly cities must provide adequate and accessible housing, transportation services and infrastructures linked to social, civic, economic, and health services and opportunities, inclusion of older people in notable social and civic positions, and open information distribution.The American Association of Retired Persons (AARP) defines a livable community, in much the same vein, as "one that has affordable and appropriate housing, supportive community features and services, and adequate mobility options, which, together facilitate personal independence and the engagement of residents in civic and social life". 5 Large, dense cities, especially in the developed world, offer more mass transit facilities and ADA paratransit than rural areas. Older residents in rural and suburban areas must rely on cars to reach almost any destination, and if unable to drive, their mobility is severely limited. At the same time, cities offer more social and civic opportunities, such as entertainment, neighborhood and community organizations, and volunteer charities, which, as the AARP report notes, are all related to successful aging. 5 Such social engagement has even been linked to improvements in physical health. 6 Research has also shown that dense urban areas with mixed uses and good pedestrian sidewalks are associated with increased walking among older residents, allowing them to engage their communities and maintain their physical health. 7-10 All of these benefits tend to be concentrated in naturally occurring retirement communities (NORCs).

By 2030, 60% of the world_s population will live in cities; 1 in such an environment, intelligent urban design is needed to encourage the health and civility of citizens. Jane Jacobs, an influential urban critic of the 20th century who passed away this past year, pioneered thoughtful and responsible city design that would build not on the imaginary theories of city planners, but on observations and records of city life. In her seminal work, The Death and Life of Great American Cities, 2 Jacobs observed how the complex interaction of multiple variables within cities affects residents_ quality of life. For Jacobs, Bhealthy^cities are ones where the physical environment is organized in a way that strengthens social networks of streets and communities to promote crime reduction and collective action.Although her ideas have had pervasive influence in urban design, criminology, and political science, their integration into public health research is only a recent phenomenon. For instance, in research on neighborhood-level health outcomes, green space often is hailed for its positive health effects (for recent examples, see Maas, et al 3 and Takano et al 4 ). In Jacobs_ conception, the possible effects are more nuanced; although parks can function as community centers when properly integrated, misallocated green space can negatively impact neighborhoods. When located in a low-traffic area such as at the residential edge of a neighborhood, parks may become havens for transient populations or criminal activity. Greenery does not automatically lead to physical activity or positive psychosocial health, and the positioning of parkland can be a driving factor in how green space is used and perceived. Jacobs_ theories have been integrated in conceptual models of mechanisms producing health outcomes, 5 but further development and testing of such models can only broaden understanding of the relationship between green space and health.