Objective: The aim of our study was to assess the prevalence of respiratory diseases in children living in a rural area in Bavaria in a systematic and standardised way to clarify whether a disease cluster exists. Reports from a parents' initiative claiming an increase of diseased children and assuming an association with air pollution due to nearby industrial sources and heavy traffic were the reason for the study.
Methods: Parents of all children living in small towns specified by the parents' initiative as affected region (central area) and parents of those children aged 6-7 or 13-14 years living in adjacent areas (control area) were asked to complete a written questionnaire. In bivariate analysis, differences in prevalences between the central area and the control area were assessed by the chi (2) test. In multivariate analysis, confounder-adjusted odds ratios with 95 % confidence intervals were calculated by logistic regression. In addition, generalized linear mixed models were used to control for potential clusters in families.
Results: The response rate was rather low (total 46 %, central area 53 %, control area 34 %). The study population comprised 121 girls and 141 boys. There was a pattern of increased prevalences of cough, wheeze and respiratory diseases caused by infections in children living in the central area compared to the control area. However, statistical significance was rarely observed. No systematic differences were observed for the prevalence of allergic rhinitis and atopic dermatitis. Selection bias due to varying response rates in the central versus the control area and information bias introduced by the preceding intensive public discussion could not be excluded. The comparison of prevalences detected in the small area with published data from other epidemiological studies in Germany did not indicate a systematically increased prevalence of respiratory symptoms or physician-diagnosed respiratory diseases in children from the whole area as well as in children from the central area only.
Conclusion: This study exemplifies the challenges of small area investigations initiated by the residential community to clarify an assumed disease cluster caused by environmental pollution. The prior comparison of small area prevalence data with results of other epidemiological studies aids the decision making as to whether a detailed study with comprehensive assessment of individual exposure is justifiable.