The impacts of fine particulate matter on ankylosing spondylitis incidence in Southwest China.

Ankylosing spondylitis (AS), a chronic inflammatory disease affecting the spine and sacroiliac joints, is influenced by both genetic and environmental factors. This study investigates the impact of air pollution and meteorological conditions on AS incidence in 14 cities across Southwest China from 2014 to 2021, focusing on immune-environmental interactions. Using a two-step approach, we applied the Fixed Effects Model to city-level data to assess the influence of air pollutants (PM10, PM2.5, SO2, NO2, CO, O3_8H) and meteorological factors (humidity, temperature, precipitation, sunshine hours) on AS incidence, and the Distributed Lag Non-Linear Model (DLNM) to individual patient data to explore non-linear and delayed effects on immune parameters. Results indicate a significant association between PM2.5 exposure and increased AS incidence, with a potential two-year lag effect and a correlation with humidity. No consistent relationships were found with other pollutants or meteorological factors. In male AS patients, PM2.5 exposure was linked to elevated monocyte counts, suggesting heightened inflammatory activity. These findings highlight PM2.5 as a potential environmental risk factor for AS, underscoring the need for targeted public health interventions.