Funding for this research was provided by:
National Institute on Aging (R01 AG042407)
Article History
Received: 23 May 2018
Accepted: 12 March 2019
First Online: 27 March 2019
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board of the University of Southern California.
: A.A.S. is a Senior Scientist with the Gallup Organization and a consultant with Adelphi Values, inc. and IQVia, inc.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.