- Correspondence to Dr Daming Wang, National Center of Gerontology, Beijing Hospital, Beijing 100730, China;
- Received November 8, 2018
- Revised December 14, 2018
- Accepted December 17, 2018
- First published January 28, 2019.
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.