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Environment
Original research
Short-term effects of outdoor air pollution on acute ischaemic stroke occurrence: a case-crossover study in Tianjin, China
  1. Xuemei Qi1,
  2. Zhongyan Wang2,
  3. Xiaokun Guo2,
  4. Xiaoshuang Xia1,
  5. Juanjuan Xue1,
  6. Guojing Jiang2,
  7. Yumeng Gu1,
  8. Suqin Han3,
  9. Qing Yao3,
  10. Ziying Cai3,
  11. Xiaojia Wang3,
  12. Lin Wang2,
  13. Sean X Leng4,
  14. Xin Li1
  1. 1 Department of Neurology, The Second Hospital of Tianjin Medical University, Tianjin, China
  2. 2 Department of Geriatrics, The Second Hospital of Tianjin Medical University, Tianjin, China
  3. 3 CMA-NKU Cooperative Laboratory for Atmospheric Environment-Health Research (CLAER/CMA-NKU), Tianjin Environmental Meteorology Center, Tianjin, China
  4. 4 Division of Geriatric Medicine and Gerontology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
  1. Correspondence to Dr Xin Li, Department of Neurology, The Second Hospital of Tianjin Medical University, Tianjin 300211, China; lixinsci{at}126.com; Dr Sean X Leng, Division of Geriatric Medicine and Gerontology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA; sleng1{at}jhmi.edu

Abstract

Objective Ambient air pollution is associated with ischaemic stroke incidence. However, most of the previous studies used stroke-related hospital admission rather than stroke onset itself. This study aimed to evaluate the relationship between ambient air pollutant exposures and acute ischaemic stroke based on the timing of symptom onset.

Methods A time-stratified, case-crossover analysis was performed among 520 patients who had ischaemic stroke admitted to the Second Hospital of Tianjin Medical University (Tianjin, China) between 1 April 2018 and 31 March 2019 (365 days). Daily air pollutant concentrations of particulate matter with aerodynamic diameter 2.5 µm, particulate matter with aerodynamic diameter 10 µm (PM10), sulfur dioxide, nitrogen dioxide, carbon monoxide and ozone were obtained from fixed-site monitoring stations. We used conditional logistic regression to estimate OR and 95% CI corresponding to an increase in IQR of each air pollutant after adjusting for the effects of temperature and relative humidity.

Results Overall, a higher risk of ischaemic stroke was found between April and September. During this period PM10 was associated with an increased risk of ischaemic stroke (1-day lag: OR=1.49, 95% CI 1.09 to 2.02; 3-day mean: OR=1.58, 95% CI 1.09 to 2.29) among patients between 34 and 70 years old. Positive associations were also observed between PM10 (1-day lag: OR=1.51, 95% CI 1.10 to 2.07; 3-day mean: OR=1.57, 95% CI 1.08 to 2.29), ozone (1-day lag: OR=1.83, 95% CI 1.16 to 2.87; 3-day mean: OR=1.90, 95% CI 1.06 to 3.42) and ischaemic stroke occurrence among those with hyperlipidaemia.

Conclusion Our results suggest that air pollution is associated with a higher risk of ischaemic stroke in younger people or people with hyperlipidemia. These findings still need to be further investigated.

  • air pollution
  • environment
http://creativecommons.org/licenses/by-nc/4.0/

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

https://doi.org/10.1136/oemed-2019-106301

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    Footnotes

    • Contributors XQ collected the data, performed the statistical analysis and drafted the manuscript. ZW, XG and XX collected the data and revised the manuscript. JX, GJ and YG collected the clinical data and revised the manuscript. SH, QY, ZC and XW collected the meteorological and air pollution data and revised the manuscript. LW revised the manuscript. SXL designed the study and revised the manuscript. XL designed the study, double-checked the statistical analysis and revised the manuscript.

    • Funding This work was supported by the Major Social Science Program of Tianjin Municipal Education Commission (grant number 2017JWZD36), Key Technology Research and Development Program of Science and Technology of Tianjin (grant number 18ZXDBSY00210), and Key Subject of Tianjin Health Committee (grant number 15KG136).

    • Competing interests None declared.

    • Patient consent for publication Not required.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Data availability statement No data are available.