Definitions of urban areas feasible for examining urban health in the European Union.

INTRODUCTION: As part of the EU-funded project, European Urban Health Indicator System (EURO-URHIS), a definition of urban areas (UAs) and of urban populations was needed to be able to identify comparable UAs in all member states. METHODS: A literature review on existing definitions, as well as those used by other relevant projects, was performed. A survey of national experts in public health or land planning was also conducted. An algorithm was proposed to find UAs, which were feasible for the focus of EURO-URHIS. RESULTS: No unique general definition of UAs was found. Different fields of research define UAs differently. None of the definitions found were feasible for EURO-URHIS. All of them were found to have critical disadvantages when applied to an urban health project. An ideal definition for this type of project needs to provide a description of the situation without recourse to administrative boundaries yet inform the collection of routine data for urban health monitoring. These requirements were found to contradict each other and were not met in any existing definition. An algorithm was developed for the definition of UAs for the purpose of this study whereby national experts would select regions which are urban as an agglomeration or as a metropolitan area and which are potentially interesting in terms of public health; identify the natural boundaries, where countryside ends and residential or commercial areas of the region begin (e.g. by aerial photos); identify local government boundaries or other official boundaries used for routine data collection purposes which approximate the natural UA as closely as possible and list all administrative areas which are contained in the larger UA. CONCLUSION: The aggregation of all administrative areas within the original region formed the UA which was used in the project.