[Is the prevalence of adult asthma increasing?]

Many studies from all over the world suggest that the prevalence of asthma, especially atopic asthma, is increasing. While this was already confirmed concerning childhood asthma, evidence of an increase in the prevalence of adult asthma is now accumulating. This phenomenon is probably related to urbanization, such as air pollution, air-tightness of dwellings and buildings, favorable environment for the propagation of mites and molds, habits of keeping furry and feathered pets, and so on. Changes in the infection patterns, including M. tuberculosis infection, especially in early childhood, might be involved in the recent prevalence of asthma. There is possibility that human population with low Th1 cell function (with relatively up-regulated Th2 function), which may be related to atopic pre-disposition, are increasing in the recent world.