1. University of Bristol, School of Social and Community Medicine, Canynge Hall, Bristol, UK
2. Department of Primary Care and Public Health, Neuadd Meirionnydd, Heath Park, Cardiff, UK
3. Section of Geriatric Medicine, Cardiff University School of Medicine, Academic Centre, University Hospital Llandough, Cardiff, UK
4. Department of Neurology, Musgrove Park Hospital, Taunton, Somerset, UK
5. London School of Hygiene and Tropical Medicine, London, UK