Stephan K. Weiland of the University of Ulm in Germany and his colleagues analyzed data collected from more than 650,000 subjects as part of the International Study of Asthma and Allergies in Childhood, which includes 155 participating centers around the world. The team compared the incidence of asthma and eczema to climate data for two groups: children between the ages of six and seven and youngsters aged 12 to 13. According to the report, for countries in western Europe each 10 percent increase in indoor humidity was linked to an almost 3 percent rise in the reported rate of asthma. What is more, cities in which the average humidity dropped below 50 percent for at least one month a year had lower rates of asthma compared to more humid locales. Higher altitude destinations and those with more variable temperatures were associated with lower asthma rates, whereas children living in cities with higher temperatures were less likely to have eczema.
Just how humidity affects asthma rates remains unclear, the authors caution, although increased exposure to dust mites and higher amounts of mold could be factors. The team notes that its study is the first to take a global view to examine the relationship between asthma and eczema and climate. The results, the authors conclude, may also have implications for the assessment of potential health effects due to climate change.