aDivision of Psychiatry, University college London, and Dementia UK

bResearch Department of Behavioural Science and Health

cDivision of Psychiatry, University College London

dFaculty of Health and Life Sciences, De Montfort University, Leicester, and Dementia UK

eGeller Institute of Ageing and Memory (GIAM), University of West London

fCentre for Psychiatry and Mental Health, Wolfson Institute of Population Health, Queen Mary University of London, London, UK

Correspondence to Pat Brown, UCL Division of Psychiatry, 6th Floor Wing A, Maple House, 149 Tottenham Court Road, London W1T7BN, UK. E-mail: [email protected]