Fig. 1

Ethical Considerations and Compliance with Guidelines: This study utilised data from the China Health and Retirement Longitudinal Study (CHARLS), which is a publicly available dataset that has been approved by the Peking University Biomedical Ethics Committee (Approval Number: IRB00001052-11015). All the study methods were performed in accordance with the relevant guidelines and regulations, including the ethical principles outlined in the “Regulations on Ethical Review of Biomedical Research Involving Human Beings”. The data that were used in this study were anonymised, and the study did not involve any direct interaction with human participants, thus ensuring the protection of participants’ privacy and confidentiality. Additionally, the use of CHARLS data complied with the guidelines for the use of harmonised datasets, which are designed to facilitate international comparative research while maintaining data integrity and ethical standards.