Do differences in the administrative structure of populations confound comparisons of geographic health inequalities?

Jackson, A.L., Davies, C.A. and Leyland, A.H. (2010) Do differences in the administrative structure of populations confound comparisons of geographic health inequalities? BMC Medical Research Methodology, 10(74), (doi:10.1186/1471-2288-10-74)

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Background: Geographical health inequalities are naturally described by the variation in health outcomes between areas (e.g. mortality rates). However, comparisons made between countries are hampered by our lack of understanding of the effect of the size of administrative units, and in particular the modifiable areal unit problem. Our objective was to assess how differences in geographic and administrative units used for disseminating data affect the description of health inequalities.

Methods: Retrospective study of standard populations and deaths aggregated by administrative regions within 20 European countries, 1990-1991. Estimated populations and deaths in males aged 0-64 were in 5 year age bands. Poisson multilevel modelling was conducted of deaths as standardised mortality ratios. The variation between regions within countries was tested for relationships with the mean region population size and the unequal distribution of populations within each country measured using Gini coefficients.

Results: There is evidence that countries whose regions vary more in population size show greater variation and hence greater apparent inequalities in mortality counts. The Gini coefficient, measuring inequalities in population size, ranged from 0.1 to 0.5 between countries; an increase of 0.1 was accompanied by a 12-14% increase in the standard deviation of the mortality rates between regions within a country.

Conclusions: Apparently differing health inequalities between two countries may be due to differences in geographical structure per se, rather than having any underlying epidemiological cause. Inequalities may be inherently greater in countries whose regions are more unequally populated.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Davies, Dr Carolyn and Leyland, Professor Alastair
Authors: Jackson, A.L., Davies, C.A., and Leyland, A.H.
College/School:College of Medical Veterinary and Life Sciences > Institute of Health and Wellbeing > MRC/CSO SPHSU
College of Medical Veterinary and Life Sciences > School of Medicine, Dentistry & Nursing > Centre for Population and Health Sciences
Journal Name:BMC Medical Research Methodology
Publisher:BioMed Central
ISSN (Online):1471-2288
Published Online:18 August 2010
Copyright Holders:Copyright © 2010 The Authors
First Published:First published in BMC Medical Research Methodology 10(74)
Publisher Policy:Reproduced under a Creative Commons License

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