1. Department of Rheumatology, Dudley Group of Hospitals NHS Trust, Russells Hall Hospital, Dudley, West Midlands, UK
2. School of Sport, Health and Exercise Sciences, Bangor University, Bangor, Gwynedd, Wales, UK
3. Wolfson Computer Laboratory, University Hospital Birmingham NHS Foundation Trust, Queen Elizabeth Hospital Birmingham, UK
4. Arthritis Research UK Epidemiology Unit, University of Manchester, Manchester, UK