Socioeconomic Inequalities\nin the External Exposome\nin European Cohorts: The EXPANSE Project

Socioeconomic inequalities in the exposome have been\nfound to be\ncomplex and highly context-specific, but studies have not been conducted\nin large population-wide cohorts from multiple countries. This study\naims to examine the external exposome, encompassing individual and\nenvironmental factors influencing health over the life course, and\nto perform dimension reduction to derive interpretable characterization\nof the external exposome for multicountry epidemiological studies.\nAnalyzing data from over 25 million individuals across seven European\ncountries including 12 administrative and traditional cohorts, we\nutilized domain-specific principal component analysis (PCA) to define\nthe external exposome, focusing on air pollution, the built environment,\nand air temperature. We conducted linear regression to estimate the\nassociation between individual- and area-level socioeconomic position\nand each domain of the external exposome. Consistent exposure patterns\nwere observed within countries, indicating the representativeness\nof traditional cohorts for air pollution and the built environment.\nHowever, cohorts with limited geographical coverage and Southern European\ncountries displayed lower temperature variability, especially in the\ncold season, compared to Northern European countries and cohorts including\na wide range of urban and rural areas. The individual- and area-level\nsocioeconomic determinants (i.e., education, income, and unemployment\nrate) of the urban exposome exhibited significant variability across\nthe European region, with area-level indicators showing stronger associations\nthan individual variables. While the PCA approach facilitated common\ninterpretations of the external exposome for air pollution and the\nbuilt environment, it was less effective for air temperature. The\ndiverse socioeconomic determinants suggest regional variations in\nenvironmental health inequities, emphasizing the need for targeted\ninterventions across European countries.