Received: 1 October 2020
Accepted: 7 April 2021
First Online: 24 May 2021
: The 2018 wave of CLHLS study was approved by the Biomedical Ethics Committee of Peking University (IRB00001052–13074). All participants or their legal representatives signed written consent forms in the baseline and follow-up surveys.
: Not Applicable.
: YY is an editorial board member of BMC Geriatrics. DG is a senior editorial board member of BMC Geriatrics.