Geographical distribution of COPD prevalence in Europe, estimated by an inverse distance weighting interpolation technique

Abstract

Existing data on COPD prevalence are limited or totally lacking in many regions of Europe. The geographic information system inverse distance weighted (IDW) interpolation technique has proved to be an effective tool in spatial distribution estimation of epidemiological variables, when real data are few and widely separated. Therefore, in order to represent cartographically the prevalence of COPD in Europe, an IDW interpolation mapping was performed. The point prevalence data provided by 62 studies from 19 countries (21 from 5 Northern European countries, 11 from 3 Western European countries, 14 from 5 Central European countries, and 16 from 6 Southern European countries) were identified using validated spirometric criteria. Despite the lack of data in many areas (including all regions of the eastern part of the continent), the IDW mapping predicted the COPD prevalence in the whole territory, even in extensive areas lacking real data. Although the quality of the data obtained from some studies may have some limitations related to different confounding factors, this methodology may be a suitable tool for obtaining epidemiological estimates that can enable us to better address this major public health problem.

Keywords: GIS; Geographic Resources Analysis Support System; epidemiology; geographic information system.

Figure 1

COPD mean prevalence in Europe. Notes: In this IDW interpolation map, the COPD prevalence is represented by a red–blue scale. Black spots indicate the places of origin of the data obtained from 62 selected studies. Some black spots are also shown in some nearby countries of North Africa and Middle East for guidance. Abbreviation: IDW, inverse distance weighting.

Figure 2

COPD mean prevalence in Europe. Note: The IDW interpolation map shows the prevalence values of COPD at the points of origin of the patients, both in Europe and in some neighboring countries in North Africa and the Middle East. Abbreviation: IDW, inverse distance weighting.

Figure 3

COPD mean prevalence in Europe. Notes: In this IDW interpolation map, spots and numerical values have been removed to allow a clearer view of the colors with which the different regions appear colored. Although there is not an exact equivalence between the qualitative data provided by the color scale and the numerical values obtained from published studies, there is an approximate correlation between them, which allows interpreting findings of the mapping with reasonable certainty. Abbreviation: IDW, inverse distance weighting.