Received: 21 July 2019
Accepted: 17 October 2019
First Online: 1 November 2019
Ethics approval and consent to participate
: The study protocol was approved by the Ethical Committee of Tokyo Metropolitan Institute of Gerontology. Participants were informed about the study purpose, method, survey items, and merits of participation. The return of the questionnaire was viewed as consent to participate in the mail-in questionnaire the survey. Written consent was received from all participants of the home-interview survey.
: Not applicable.
: The authors declare that they have no competing interest.