Association of short-term exposure to ambient fine particle matter with hospital admission risks and costs in China, a case-crossover study

As Fine particulate matter (PM_2.5) levels declined in China in past years, the health and social benefits brought about by the air quality improvement are beginning to emerge. We did a time-stratified, case-crossover study which including in total of 106, 120, 862 hospital admissions from 1040 class 3 hospitals in 268 cities, 31 provinces in China, from January 1, 2013 to December 31, 2017, obtained from High Quality Monitoring System (HQMS). We obtained PM_2.5 and ozone concentrations from a high-resolution model and joined daily air pollution estimates for each patient based on hospital location. To assess the association between main air pollutants and hospital admission, hospital days, and hospitalization expenses, we applied conditional logistic regressions to perform a risk assessment associated with main pollutants (PM_2.5 and Ozone) in two-pollutant models. The results show that the risk of hospital admission was positively associated with short-term exposure to PM_2.5 in all major diseases. Specifically, every 10 μg/m³ increase in the concentration level of PM_2.5 (adjusted for ozone) was associated with 0.27% (95% CI: 0.25%, 0.29%) increase in hospital admission, 39.00 (95% CI: 36.11, 41.89) yuan increase in hospitalization expense per admission, and 0.0280 (95% CI: 0.0259, 0.0300) days increase in hospital days per admission. Moreover, the relative risk increases of mental disorders, respiratory diseases and circulatory diseases showed significant associations with short-term PM_2.5 exposure. Based on our calculations, improved air quality since 2013 saved 2.28 billion yuan in medical expenses in 2017.