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Journal of Cancer Epidemiology
Volume 2013 (2013), Article ID 612514, 6 pages
http://dx.doi.org/10.1155/2013/612514
Research Article

The Impact of Adjustment for Socioeconomic Status on Comparisons of Cancer Incidence between Two European Countries

1Northern Ireland Cancer Registry, Centre for Public Health, Mulhouse Building, Grosvenor Road, Belfast BT12 6DP, UK
2MACSI, Department of Mathematics and Statistics, University of Limerick, Limerick, Ireland
3National Cancer Registry, Building 6800, Cork Airport Business Park, Kinsale Road, Cork, Ireland
4Centre for Research in Environmental Epidemiology (CREAL), Barcelona, Spain
5CIBER Epidemiología y Salud Pública (CIBERESP), Barcelona, Spain

Received 12 September 2013; Accepted 11 November 2013

Academic Editor: T. L. Vaughan

Copyright © 2013 David W. Donnelly et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Background. Cancer incidence rates vary considerably between countries and by socioeconomic status (SES). We investigate the impact of SES upon the relative cancer risk in two neighbouring countries. Methods. Data on 229,824 cases for 16 cancers diagnosed in 1995–2007 were extracted from the cancer registries in Northern Ireland (NI) and Republic of Ireland (RoI). Cancers in the two countries were compared using incidence rate ratios (IRRs) adjusted for age and age plus area-based SES. Results. Adjusting for SES in addition to age had a considerable impact on NI/RoI comparisons for cancers strongly related to SES. Before SES adjustment, lung cancer incidence rates were 11% higher for males and 7% higher for females in NI, while after adjustment, the IRR was not statistically significant. Cervical cancer rates were lower in NI than in RoI after adjustment for age (IRR: 0.90 (0.84–0.97)), with this difference increasing after adjustment for SES (IRR: 0.85 (0.79–0.92)). For cancers with a weak or nonexistent relationship to SES, adjustment for SES made little difference to the IRR. Conclusion. Socioeconomic factors explain some international variations but also obscure other crucial differences; thus, adjustment for these factors should not become part of international comparisons.