1 Centre for Primary Care and Public Health, Barts and The London School of Medicine & Dentistry, Londres, Reino Unido; The Westborough Road Medical Centre, Westcliff-on-Sea, Reino Unido. Electronic address: l.garcia-morzon@qmul.ac.uk.
2 The Westborough Road Medical Centre, Westcliff-on-Sea, Reino Unido.
4 Centro de Salud Universitario Villanueva de la Cañada, Departamento de Medicina, Universidad Autónoma de Madrid, Villanueva de la Cañada, Madrid, España.