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