Short-term ozone exposure on stroke mortality and mitigation by greenness in rural and urban areas of Shandong Province, China

Short-term exposure to ozone (O 3 ) has been associated with higher stroke mortality, but it is unclear whether this association differs between urban and rural areas. The study aimed to compare the association between short-term exposure to O 3 and ischaemic and haemorrhagic stroke mortality across rural and urban areas and further investigate the potential impacts of modifiers, such as greenness, on this association. A multi-county time-series analysis was carried out in 19 counties of Shandong Province from 2013 to 2019. First, we employed generalized additive models (GAMs) to assess the effects of O 3 on stroke mortality in each county. We performed random-effects meta-analyses to pool estimates to counties and compare differences in rural and urban areas. Furthermore, a meta-regression model was utilized to assess the moderating effects of county-level features. Short-term O 3 exposure was found to be associated with increased mortality for both stroke subtypes. For each 10-µg/m 3 (lag0-3) rise in O 3 , ischaemic stroke mortality rose by 1.472% in rural areas and 1.279% in urban areas. For each 0.1-unit increase in the Enhanced Vegetation Index (EVI) per county, the ischaemic stroke mortality caused by a 10-µg/m 3 rise in O 3 decreased by 0.60% overall and 1.50% in urban areas. Our findings add to the evidence that short-term O 3 exposure increases ischaemic and haemorrhagic stroke mortality and has adverse effects in urban and rural areas. However, improving greenness levels may contribute to mitigating the detrimental effects of O 3 on ischaemic stroke mortality.