Footnotes

• Contributors Both authors contributed to the writing of this paper.

• Funding This work was supported by the National Institute for Health Research (NIHR) Biomedical Research unit in Dementia based at University College London Hospitals (UCLH) and University College London (UCL). The views expressed by the authors are not necessarily those of the NHS, NIHR or the Department of Health. Dr Schott is a HEFCE Clinical Senior Lecturer and receives funding from Alzheimer's Research UK and the Alzheimer's Society. Dr Warren is in receipt of a Wellcome Trust Senior Clinical Fellowship (Grant No. 091673/Z/10/Z).

• Competing interest None.

• Provenance and peer review Commissioned, externally reviewed.