| Spatial Epidemiology: Current Approaches and Future Challenges Paul Elliott1 and Daniel Wartenberg2 1Small Area Health Statistics Unit, Department of Epidemiology and
Public Health, Imperial College London, London, United Kingdom; 2Environmental
and Occupational Health Sciences Institute and The Cancer Institute of New
Jersey, University of Medicine and Dentistry of New Jersey, Robert Wood Johnson
Medical School, Piscataway, New Jersey, USA Abstract
Spatial epidemiology is the description and analysis of geographic variations in disease with respect to demographic, environmental, behavioral, socioeconomic, genetic, and infectious risk factors. We focus on small-area analyses, encompassing disease mapping, geographic correlation studies, disease clusters, and clustering. Advances in geographic information systems, statistical methodology, and availability of high-resolution, geographically referenced health and environmental quality data have created unprecedented new opportunities to investigate environmental and other factors in explaining local geographic variations in disease. They also present new challenges. Problems include the large random component that may predominate disease rates across small areas. Though this can be dealt with appropriately using Bayesian statistics to provide smooth estimates of disease risks, sensitivity to detect areas at high risk is limited when expected numbers of cases are small. Potential biases and confounding, particularly due to socioeconomic factors, and a detailed understanding of data quality are important. Data errors can result in large apparent disease excess in a locality. Disease cluster reports often arise nonsystematically because of media, physician, or public concern. One ready means of investigating such concerns is the replication of analyses in different areas based on routine data, as is done in the United Kingdom through the Small Area Health Statistics Unit (and increasingly in other European countries, e.g., through the European Health and Environment Information System collaboration) . In the future, developments in exposure modeling and mapping, enhanced study designs, and new methods of surveillance of large health databases promise to improve our ability to understand the complex relationships of environment to health. Key words: disease clusters, disease mapping, environmental pollution, epidemiology, geographic studies, methods. Environ Health Perspect 112:998-1006 (2004) . doi:10.1289/ehp.6735 available via http://dx.doi.org/ [Online 15 April 2004]
This article is part of the mini-monograph "Health and Environment Information Systems for Exposure and Disease Mapping, and Risk Assessment." Address correspondence to P. Elliott, Small Area Health Statistics Unit, Department of Epidemiology and Public Health, Imperial College London, Faculty of Medicine, St. Mary's Campus, Norfolk Place, London W2 1PG, United Kingdom. Telephone: 44 0 20 75943328. Fax: 44 0 20 7262 1034. E-mail: p.elliott@imperial.ac.uk The Small Area Health Statistics Unit is funded by a grant from the Department of Health, Department of the Environment, Food and Rural Affairs, Environment Agency, Health and Safety Executive, Scottish Executive, Welsh Assembly Government, and Northern Ireland Department of Health, Social Services and Public Safety. This research was also supported by grants R01 CA92693 from the National Cancer Institute and U61/ATU272387 from the Agency for Toxic Substances and Disease Registry, Centers for Disease Control and Prevention, to D.W. The views expressed in this publication are those of the authors and not necessarily those of the funding bodies. The authors declare they have no competing financial interests. Received 12 September 2003 ; accepted 15 April 2004.
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