Background: A basic assumption was that exposure to the indoor environment would increase the manifestation of respiratory symptoms in predisposed individuals. The aim was to investigate the proportion of perceived respiratory symptoms attributed to specific environmental exposures, and associations related to indoor climate risk indicators, i.e. occurrence of damp or mould, insufficient ventilation and condensation on windows.
Method: A questionnaire was mailed to a random sample of 8008 individuals, stratified for gender and age. The response rate was 84% (n=6732). Established criteria for current asthma were used to classify subjects into three subgroups: asthmatics, healthy and symptomatics (but without current asthma).
Results: The proportion of symptoms attributed to specific environmental exposures increased in the total sample and in the three subgroups when indoor climate risk indicators, particularly damp or mould, were reported. Generally, the lowest proportions were found for healthy and the highest for asthmatics. Univariate analyses presented as relative risks (RR) (95% CI) showed significantly increased risks for perceived overall influence on airways for all groups, with RR ranging from 4.3 to 6.8. Although respiratory symptoms attributed to dust, environmental tobacco smoke (ETS) and strong scents increased when risk indicators were reported, RR were generally lower in all groups.
Conclusion: The high frequency of respiratory symptoms among asthmatics increased when occurrences of risk indicators were reported. Similarly, increased symptoms were found for healthy indicating that indoor climate risk indicators may affect both healthy and unhealthy individuals.