Asthma and respiratory symptoms related to the housing environment

Abstract: The overall aim of this dissertation was to study the housing environment with a focus on indoor climate factors which may maintain or worsen respiratory symptoms among persons with asthma.Quasi-experimental and cross-sectional designs and a case-control approach were used. In Study I data was collected from a consecutive series of patients with asthma (n=21) and in the three other studies from a randomly selected sample, representative of the general population (n=6732). This sample was classified into subgroups (Study II): persons with asthma (n=261), healthy persons (n=5266) and persons with symptoms (n=1205). In Study III persons with asthma (n=49) were compared to persons without asthma (n=48), and the same group, persons with asthma (n=49) was also included in Study IV. Data were gathered using subjective information from diaries and questionnaires as well as objective measurements of medical and environmental factors.Lung function was improved and there was a tendency for the indoor climate to improve after the removal of textile wall-to-wall carpets or the increase of air exchange rate. No statistically significant differences were found in the housing environment when persons with and without asthma were compared. However in some individual homes, environmental factors at levels that could increase symptoms were identified. In single-family houses higher levels of humidity, insufficient ventilation and the occurrence of house dust mites indicated a less favorable indoor climate compared to multi-family houses. Respiratory symptoms attributed to specific environmental exposures increased in both healthy and unhealthy persons when they reported occurrence of indoor climate risk indicators. No statistically significant associations were found between separate risk indicators, identified by a ‘Housing Environmental-index’, or the frequency of indicators and clinical tests. The lack of significant associations may show that the chosen cut-off levels in the index were too high in reference to persons with asthma and further research is needed to establish relevant cut-off levels.In some of the investigated houses there was a need for secondary preventive interventions to improve the indoor climate in order to decrease the exposure of allergens and airway irritants. In this dissertation one aspect of the complex relationship between the person and the environment, i.e. accessibility, has been studied. Further research is needed to address the aspect of usability, i.e. the person’s own evaluation of the degree to which they can be in and use the environment.