Measures of indoor dampness and asthma symptoms in children: A meta-analysis

Rationale: Numerous studies have shown relationships between indoor dampness or mold and respiratory symptoms in children. However, this relationship is currently not well understood due to the heterogeneity in study designs across the literature. Objective: Systematically examine the association between measures of indoor dampness and respiratory symptoms in children and explore reasons for differences in measures of effect across observational studies. Methods: We identified relevant articles in a MEDLINE search using the MESH headings asthma, fungi or humidity, and the keywords indoor or wheezing. Information on study design, participant characteristics, and exposure and outcome assessment was extracted in duplicate. A random effects model was used to pool data from individual studies both for a main analysis and for apriori identified subgroup analyses. Results: 7 out of 66 retrieved articles met our eligibility criteria. The pooled odds ratio (OR) (1.6; 95% confidence interval (CI), 1.2, 2.2) indicates that indoor dampness is a risk factor for respiratory symptoms with significant heterogeneity (p<0.001) across studies. The pooled OR was higher when "wheezing symptoms" was used as the outcome of interest than when "doctor diagnosed asthma" was used as the study outcome. There was little difference in the pooled OR by exposure definition (dampness vs. mold). Conclusions: Exposure to elevated levels of dampness or mold appears to increase the odds of respiratory symptoms in children. However, these results may be systematically biased away from the null due to differential reporting of exposure or outcome. Future studies should use standardized tools which measure exposure cumulatively.