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Article History

Received: 14 May 2024

Accepted: 29 April 2026

First Online: 21 May 2026

Competing interests

: The authors declare no competing interests.

: This study is based on secondary data from the China Health and Retirement Longitudinal Study (CHARLS) and the China City Statistical Yearbook. The CHARLS survey was approved by the Biomedical Ethics Review Committee of Peking University (IRB00001052-11015). All procedures involving human participants were conducted in accordance with the ethical standards of the institutional research committee and with the Declaration of Helsinki. The present study uses anonymized, publicly available secondary data and does not involve direct interaction with human participants. The China City Statistical Yearbook data are publicly available aggregated statistical data published by the National Bureau of Statistics of China and contain no individual-level information. Therefore, no ethical approval was required.

: Informed consent was obtained from all participants in the original CHARLS survey at the time of data collection. For the present study, only de-identified secondary data were used, and no additional informed consent was required. The China City Statistical Yearbook data do not involve human participants and are publicly available in aggregated form. Therefore, informed consent was not applicable.