Received: 28 March 2019
Accepted: 14 June 2019
First Online: 15 July 2019
Ethics approval and consent to participate
: No ethical approval was required for this systematic review of existing published literature.
: Not applicable
: All authors have completed the ICMJE uniform disclosure form at ExternalRef removed and declare HS reports funds from the UCL Dementia Scholarship 2017. GL has grants from the National Institute for Health Research (NIHR)/Economic and Social Research Council, NIHR Health Technology Assessment and Alzheimer’s Society and is supported by the North Thames NIHR Collaboration for Leadership in Applied Health Research and Care. AS reports grants from the Wellcome Trust. GL and AS are supported by the University College London Hospitals NIHR Biomedical Research Centre.