1. Centre for Mental Health, Claybrook Centre, Imperial College London; Ageing Research Unit, Faculty of Epidemiology and Public Health, Imperial College London; West London Cognitive Disorders Treatment and Research Unit, Brentford Lodge, West London Mental Health Trust, London, UK
2. Imperial Clinical Trials Unit, School of Public Health, Imperial College London, UK
3. Ageing Research Unit, Faculty of Epidemiology and Public Health, Imperial College London, UK
4. Centre for Mental Health, Claybrook Centre, Imperial College London, 37 Claybrook Road, Hammersmith, London W6 8LN, UK; West London Cognitive Disorders Treatment and Research Unit, Brentford Lodge, West London Mental Health Trust, London, UK