Updates are available Correction dated 2021-04-16

Article History

Received: 16 May 2019

Accepted: 1 December 2020

First Online: 2 January 2021

Change Date: 24 February 2021

Change Type: Update

Change Details: Figure 2 was published based on incorrect file with lower quality and incorrect legends. This article has been updated to correct this error.

Change Date: 16 April 2021

Change Type: Correction

Change Details: A Correction to this paper has been published:

Change Details: https://doi.org/10.1186/s12877-021-02167-0

Ethics approval and consent to participate

: The research design and methods were reviewed and approved by the LSE Research Ethics board, as per guidance at the time. The work was conducted shortly prior to the introduction of the Research Governance Framework, now superseded by the UK Policy Framework for Health and Social Care Research. Written consent to participate was obtained from participants – or where necessary, their proxies.

: Not applicable.

: The author declares no competing interests.