| Exploring Associations between Residential Location and Breast Cancer Incidence in a Case-Control Study Christopher Paulu,1 Ann Aschengrau,2 and David Ozonoff1 1Department of Environmental Health and 2Department of Epidemiology and Biostatistics, Boston University School of Public Health, Boston, Massachusetts, USA Abstract
Locating geographic hot spots of cancer may lead to new causal hypotheses and ultimately to new knowledge of cancer-causing factors. The Cape Cod region of Massachusetts has experienced elevated incidence of breast cancer compared with statewide averages. The origins of the excess remain largely unexplained, even after the Upper Cape Cod Cancer Incidence Study investigated numerous potential environmental exposures. Using case-control data from this study (258 cases and 686 controls) , we developed an exploratory approach for measuring associations between residential location and breast cancer incidence, adjusting for individual-level risk factors. We measured crude and adjusted odds ratios over the study region using fixed-scale grids and a smoothing algorithm of overlapping circular units. Polycircular hot spot regions, derived from the peak values of the smoothed odds ratios, delineated geographic areas wherein residence was associated with 60% [odds ratio (OR) , 1.6 ; 95% confidence interval (CI) , 0.8-3.2] to 210% (OR, 3.1 ; 95% CI, 1.3-7.2) increased incidence relative to the remainder of the study population. The findings suggest several directions for further research, including the identification of potential environmental exposures that may be assessed in forthcoming case-control studies. Key words: breast cancer, case-control studies, cluster analysis, epidemiologic methods, spatial analysis. Environ Health Perspect 110:471-478 (2002) . [Online 1 April 2002] http://ehpnet1.niehs.nih.gov/docs/2002/110p471-478paulu/ abstract.html Address correspondence to C. Paulu, Environmental Toxicology Program, Bureau of Health, State of Maine, Key Plaza, 8th Floor, 11 State House Station, Augusta, ME 04333-0011 USA. Telephone: (207) 287-9932. E-mail: cpaulu@mac.com We gratefully acknowledge the study participants, who gave their valuable time and the benefit of their experience. We also thank P. Cyr and C. Barsotti for their assistance in digitizing location data, and N. Maxwell, R. Clapp, and D. Kriebel for their comments on the manuscript. This publication was made possible by grant 2P42 ES07381 from the National Institute of Environmental Health Sciences (NIEHS) , National Institutes of Health (NIH) , with funds from the U.S. Environmental Protection Agency (U.S. EPA) . Support for this work was also provided by Silent Spring Institute with funds appropriated by the Massachusetts legislature and administered by the Massachusetts Department of Public Health (DPH) . The contents of this article are solely the responsibility of the authors and do not necessarily represent the official views of the NIEHS, NIH, U.S. EPA, Massachusetts DPH, or Silent Spring Institute. Received 10 July 2000 ; accepted 16 November 2001.
The full version of this article is available for free in HTML or PDF formats. |
