The impact of ozone pollution on stroke hospitalization

ABSTRACT

This study is one of the first to examine the causal impact of ozone pollution on stroke hospitalization in a developing country, using individual-level inpatient medical records from a major Chinese city. Employing an instrumental variable (IV) approach with thermal inversion to address potential endogeneity in air pollution, our findings reveal ozone pollution has statistically significant effect on total health expenses across all exposure intervals, spanning from 1 day to 14 days. The impact of exposure to ozone pollution for less than 7 days on total expenses can be primarily attributed to changes in daily expenses, while the impact of exposure for more than 7 days is associated with an increase in the length of hospital stay. This effect, largely driven by out-of-pocket spending on medication and examination costs, is more salient for females and ischemic stroke patients.

KEYWORDS:

• Ozone pollution
• medical expenses
• length of hospital stay
• China

JEL CLASSIFICATION:

• I10
• Q53
• Q51

Acknowledgments

We acknowledge the National Tibetan Plateau/Third Pole Environment Data Center (http://data.tpdc.ac.cn) for providing us with the CHAP data.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1. Guangzhou, the capital city of Guangdong province, is a prefecture-level city located in the PRD region of China. Guangzhou is recognized as one of the four most developed ‘‘Tier-1’ cities in China (along with Beijing, Shanghai, and Shenzhen).

2. Please refer to Huang et al. (2023) for detailed information about the database.

3. The detailed information regarding ICD-10 codes is available on the website of the National Healthcare Security Administration at https://code.nhsa.gov.cn/jbzd/public/dataWesterSearch.html.

4. The ICD codes for stroke used in this paper included I60, I61, I62, I63, I64, I65, I66, I69.0, I69.1, I69.2, I69.3, I69.4, and Z82.3.

5. Referring to Yu et al. (2019), the existing literature commonly uses the most comfortable temperature bin as the reference group. Therefore, we adopt the 14–20°C bin as our omitted group.

6. Given the circumstance of obtaining medical treatment in a city other than one’s own, residences are located across various cities within Guangdong Province.

7. The numerical results are presented in Table A2 of the Appendix A. The corresponding OLS estimates are shown in Table A1 of the Appendix A.

8. The ICD-10 codes for hemorrhagic stroke include I60, I61, I62, I69.0, I69.1, and I69.2. The ICD-10 codes for ischemic stroke include I63, I64, I69.3, and I69.4.

Additional information

Funding

Xin Zhang acknowledges the financial support from the National Natural Science Foundation of China [72003014].