Epidemiology without borders : an anational view of global health

BACKGROUND: Most analyses of global health use country as a unit of observation, not least because countries are intrinsic to health services and to many international organisations. However, this can mask geographical influences on population health, which do not respect political boundaries. METHODS: A global anational database was constructed with one degree cells of latitude and longitude, and used to calculate densities for population and key health indicators. These data were aggregated into 240 15 degrees ansectors, 171 of which were populated. Differences in ansector rank orders between population density and health outcomes (infant, maternal and HIV-related deaths and income) were calculated and mapped as quintiles. FINDINGS: Individual ansectors contained parts of 1-21 countries. Mapping by ansector showed that the four outcomes analysed were strongly geographically correlated. Sub-Saharan Africa was consistently disadvantaged in terms of health outcomes, while the Indian sub-continent was at an advantage in terms of HIV mortality, despite poverty. INTERPRETATION: Although in most cases it makes sense to analyse health on a national basis, these findings highlight the often unquestioned assumptions involved in doing so. Even if global patterns of health do not turn out so differently when analysed anationally, some major effects on health, such as climate change, are not nationally based, and should not necessarily be nationally analysed. Progress towards Millennium Development Goals must be evaluated on a population basis, rather than by counting countries achieving targets. Data files are available in Excel format and attached as separate files to this paper (see Supplementary files under Reading Tools online)