Evolving relationships between air pollution attenuation and AECOPD hospitalizations during a stringent control period in Shijiazhuang, China, 2017–2024

Background Shijiazhuang, a typical industrial city, faced severe air pollution that elevated AECOPD risk. The period 2017–2024 coincided with stringent air pollution control, providing a key window to examine the evolving relationship between air quality improvements and AECOPD hospitalizations. Methods We analyzed 57,782 AECOPD hospitalizations (2017–2024) and air pollution data using a generalized additive Poisson time-series model. The analysis incorporated distributed lag non-linear terms while adjusting for meteorological conditions, seasonal trends, and day-of-week effects, with sensitivity analyses confirming result reliability. Results PM 2.5 , PM10, and SO 2 concentrations fell by 46%, 68%, and 85%, respectively. PM 2.5 -attributable excess cases under WHO standards dropped by 37.1%. Crucially, the association strength (relative risk) between most pollutants and hospitalizations showed a significant attenuating trend over time. Conclusion During this stringent air pollution control period in Shijiazhuang, marked air quality improvements were associated with reduced AECOPD hospitalizations and attenuated pollutant-health associations. Persistent ozone pollution highlights the need for coordinated VOC-NO x management.