Published on in Vol 8, No 10 (2020): October
Preprints (earlier versions) of this paper are
available at
https://preprints.jmir.org/preprint/21759, first published
.
1 The Key Laboratory of Geriatrics, Beijing Institute of Geriatrics, Beijing Hospital, National Center of Gerontology, National Health Commission, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, China