Ambient particulate matter pollution of different sizes associated with recurrent stroke hospitalization in China: A cohort study of 1.07 million stroke patients

To estimate the associations between ambient particulate matter (PM) pollution of different sizes (PM1, PM2.5, and PM10) and risk of rehospitalization among stroke patients, as well as the attributable burden in China. We built a cohort of 1,066,752 participants with an index stroke hospitalization in Sichuan, China from 2017 to 2019. Seven-day and annual average exposures to PM pollution prior to the date of the index hospitalization were linked with residential address using a bilinear interpolation approach. Cox proportional hazard models were constructed to assess the association between ambient PM and the risk of rehospitalization. The burden of stroke rehospitalization was estimated using a counterfactual approach. 245,457 (23.0 %) participants experienced rehospitalization during a mean of 1.15 years (SD: 0.90 years) of follow-up. Seven-day average concentrations of PM were associated with increased risk of rehospitalization: the hazard ratios (HRs) per 10 μg/m3 were 1.034 (95 % confidence interval [CI]: 1.029–1.038) for PM1, 1.033 (1.031–1.036) for PM2.5, and 1.030 (1.028–1.031) for PM10; the hazard ratios were larger for annual average concentrations: 1.082 (1.074–1.090) for PM1, 1.109 (1.104–1.114) for PM2.5, and 1.103 (1.099–1.106) for PM10. The associations were stronger in participants who were female, of minority ethnicity (non-Han Chinese), who suffered from an ischemic stroke, and those admitted under normal conditions. Population attributable fractions for stroke rehospitalization ranged from 4.66 % (95 % CI: 1.69 % to 7.63 %) for the 7-day average of PM1 to 17.05 % (14.27 % to 19.83 %) for the annual average of PM10; the reducible average cost of rehospitalization per participant attributable to PM ranged from 492.09 (178.19 to 806) RMB for the 7-day average of PM1 to 1801.65 (1507.89 to 2095.41) RMB for the annual average of PM10. Ambient PM pollution may increase the risk of rehospitalization in stroke patients and is responsible for a significant burden of stroke rehospitalization.