Global Asthma Disparities: Deciphering the Multifaceted Environmental Exposome Between Eastern and Western Populations.

Early-life environmental exposures are critical determinants of the onset of childhood asthma, with risk patterns demonstrating significant heterogeneity across geographical and socioeconomic landscapes. While the "hygiene hypothesis" has long framed the rural-urban disparity-where urban children typically show higher asthma prevalence than their rural counterparts-this dichotomy is being reshaped by rapid globalization and urbanization. Furthermore, this pattern differs markedly between high-income countries (HICs) and low- and middle-income countries (LMICs). In HICs, the environmental distinction is sharp, with urban environments often characterized by a scarcity of protective microbial factors coupled with an accumulation of anthropogenic pollutants. In contrast, within developing economies undergoing rapid transition, the boundaries between rural and urban areas are increasingly blurred, and environmental exposures often involve a complex interaction among protective and risk factors. These divergent pathways are further complicated by socioeconomic inequities. This review summarizes the global burden of asthma, compares the multi-dimensional determinants across rural and urban environments in HICs (the West) and LMICs (the East), and constructs a refined risk map. It also seeks to identify key characteristics with potential for public health intervention, thereby providing a scientific basis for developing targeted asthma prevention strategies tailored to varying socioeconomic contexts.