Objectives:

To conduct a systematic review and a meta-analysis of observational and experimental studies that explore the relation between asthma and cold exposure.

Materials and methods:

Systematic review of experimental and observational studies published up to August 2015 in Pubmed, Embase and Lilacs. Two researchers selected studies that measured the occurrence of asthma in individuals exposed to different environmental temperatures. A meta-analysis used RevMan 5.3's random effects model to calculate a summary weighted Odds Ratio with 95% confidence intervals, and a sensitivity analysis identified the influence of each study. Subsequent subgroup analyses identified summary measures by type of cold exposure and study design. Additional analysis measured heterogeneity and risk of bias.

Results:

We found 86 studies measuring the relation between cold exposure and asthma. We included 11.6% (10/86) of the studies in the meta-analysis and found an association between cold exposure and asthma with all the studies (ORw 2.0 95%CI 1.28-3.14), with the subgroup of experimental studies (ORw 3.8 IC95% 1.70-8.86), and with cold environmental air (ORw 1.59 IC95% 1.10-2.30). The studies had high risk of bias and statistical heterogeneity [I2: 63.1% (27%-81.4%)].

Conclusions:

The results support the hypothesis of an association between asthma and cold exposure. This study encourages to explore the concepts proposed by traditional medicine to establish its benefits on prevention and care of respiratory diseases, such as asthma.

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