title: Can a deprivation index be used legitimately over both urban and rural areas?
abstract: BACKGROUND
  Although widely used, area-based deprivation indices remain sensitive to urban-rural differences as such indices are usually standardised around typical urban values. There is, therefore, a need to determine to what extent available deprivation indices can be used legitimately over both urban and rural areas.
  
  
  METHODS
  This study was carried out in Brittany, France, a relatively affluent region that contains deep rural areas. Among the 1,736 residential census block groups (IRIS) composing the Brittany region, 1,005 (57.9%) are rural. Four deprivation indices were calculated: two scores (Carstairs and Townsend) developed in the UK and two more recent French measures (Havard and Rey). Two standardisation levels were considered: all of the IRIS and only the urban IRIS of the region. Internal validity (Kappa coefficients and entropy values) and external validity (relationship with colorectal cancer screening [CCS] attendance) were investigated.
  
  
  RESULTS
  Regardless of the deprivation measure used, wealthy areas are mostly clustered in the West and at the outskirts of major towns. Carstairs and Rey scores stand out by all evaluation criteria, capturing both urban and rural deprivation. High levels of agreements were found across standardisation levels (κ = 0.96). The distributions of deprivation scores were balanced across urban and rural areas, and high Shannon entropy values were observed in the capital city (≥0.93). Similar and significant negative trends were observed between CCS attendance and both deprivation indices, independent of the degree of urbanisation.
  
  
  CONCLUSIONS
  These results provide support, despite potential sociological objections, for the use of a compromise index that would facilitate comparisons and interpretations across urban and rural locations in public health research.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Bertin
authors.forename: Cécile
authors.initials: C
authors.lastname: Chevrier
authors.forename: Fabienne
authors.initials: F
authors.lastname: Pelé
authors.forename: Tania
authors.initials: T
authors.lastname: Serrano-Chavez
authors.forename: Sylvaine
authors.initials: S
authors.lastname: Cordier
authors.affiliation: INSERM-IRSET n° 1085, "Epidemiological Research on Environment, Reproduction and Development", University of Rennes 1, Rennes, France. jean-francois.viel@univ-rennes1.fr.
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Viel
mesh_terms: D000368:Aged; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000191:economics* / Q000453:epidemiology*; D005260:Female; D005602:France / Q000453:epidemiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012424:Rural Population; D012959:Socioeconomic Factors; D014505:Urban Population