REFINING OF ASTHMA PREVALENCE SPATIAL DISTRIBUTION AND VISUALIZATION OF OUTDOOR ENVIRONMENT FACTORS USING GIS AND ITS APPLICATION FOR IDENTIFICATION OF MUTUAL ASSOCIATIONS.

INTRODUCTIONAsthma is a heterogeneous disease, usually characterized by chronic airway inflammation. It is defined by the history of respiratory symptoms such as wheeze, shortness of breath, chest tightness and cough that vary over time and in intensity, together with variable expiratory airflow limitation. 1-18% of the populations in different countries suffer from this chronic respiratory disease. It is generally believed that a disease inception and persistence is driven by gene-environment interactions. The most important of these interactions may occur in early life and even in-utero. Multiple environmental factors, both biological and sociological, may be important in the development of asthma (1).In the Czech Republic, numbers of registered asthmatics progressively increase especially in children, as annually monitored by the Institute of Health Information and Statistics of the Czech Republic (IHIS). 1.94% of asthmatic children (aged 0-14 years) and 1.68% of asthmatics among youth (aged 15-19 years) were registered by general practitioners for children and youth in the Czech Republic in 2000. In 2012, the proportion increased to 4.28% in children and 7.29% in youth. The highest values were reported from Hradec Kralove and Karlovy Vary Regions, the lowest from Zlin Region (2, 3). A prevalence study of the National Institute of Public Health (NIPH) presents asthma occurrence in children aged 5, 9, 13 in the year 1996 as 3.9%, in 2001 as 5.1%, in 2006 as 8.2%, and in 2012 as 9.6% (4). Higher asthma occurrence is generally thought to be related to the deterioration of environmental conditions, as proved by a number of studies. The most often discussed hazard factors are air pollutants emitted from the traffic and industry. There are connections between asthma occurrence and particulate matter less than 10 μm in aerodynamicdiameter (PM10) and smaller (5-10), NO2 (5, 11-14) and SO2 (6). Generally, the quality of the environment is also affected by other parameters like land use and agricultural production (15, 16).A very useful tool for the assessment of connections between disease occurrence and quality of the environment is the Geo- graphical Information Systems (GIS). GIS is used for health data processing, analysis of geographical distribution and variation of diseases mapping, monitoring and management of health epidemics. In addition, this system makes it possible to combine the spatial localization of the monitored disease and layers with information about the quality of the environment (7, 10, 14, 16-19).In this paper, we present an application of GIS analyses for refining asthma prevalence spatial distribution in the Czech Republic and for visualization of environmental factors which can be connected with the disease occurrence. All data were converted into the grid 1 × 1 km and joined with the grid number as a unique indicator. The result of data integration was a data set which contains the information about disease prevalence and all monitored characteristics of the outdoor environment for each spatial unit (grid). This data set served for statistical evaluation of associations between asthma prevalence and particular factors of the environment.MATERIAL AND METHODSAsthma Prevalence DataData from NIPH cross-sectional questionnaires as well as data annually reported by all general practitioners for children and youth and gathered by IHIS were processed for this study. The asthma occurrence was visualized based on the child's residence or paediatrician surgery address.The NIPH cross-section questionnaire survey was performed in five-year intervals in the framework of the Environmental Health Monitoring System in the Czech Republic, when anamnesis (including the information about asthma occurrence) of a representative sample of children aged 5, 9, 13 and 17 was obtained from the surgeries of selected paediatricians. According to the methodology of given survey, respondents were localized only by the address of responsible nursing paediatricians in 2006 and 2011, and in the year 2012, the collected data was also supplemented by the child's residence address for a further specification (Table 1). …