Formaldehyde exposure and asthma in children: a systematic review.

OBJECTIVE

Despite multiple published studies regarding the association between formaldehyde exposure and childhood asthma, a consistent association has not been identified. Here we report the results of a systematic review of published literature in order to provide a more comprehensive picture of this relationship.

DATA SOURCES

After a comprehensive literature search, we identified seven peer-reviewed studies providing quantitative results regarding the association between formaldehyde exposure and asthma in children. Studies were heterogeneous with respect to the definition of asthma (e.g., self-report, physician diagnosis). Most of the studies were cross-sectional.

DATA EXTRACTION

For each study, an odds ratio (OR) and 95% confidence interval (CI) for asthma were either abstracted from published results or calculated based on the data provided. Characteristics regarding the study design and population were also abstracted.

DATA SYNTHESIS

We used fixed- and random-effects models to calculate pooled ORs and 95% CIs; measures of heterogeneity were also calculated. A fixed-effects model produced an OR of 1.03 (95% CI, 1.021.04), and random effects model produced an OR of 1.17 (95% CI, 1.011.36), both reflecting an increase of 10 microg/m3 of formaldehyde. Both the Q and I2 statistics indicated a moderate amount of heterogeneity.

CONCLUSIONS

Results indicate a significant positive association between formaldehyde exposure and childhood asthma. Given the largely cross-sectional nature of the studies underlying this meta-analysis, further well-designed prospective epidemiologic studies are needed.