1. Universidad Católica de la Santísima; Concepción Chile
2. Autonomous University of Barcelona; Doctoral Program in Research Methodology and Public Health; Barcelona Spain
3. University of the Basque Country; Department of Preventive Medicine and Public Health; Barrio Sarriena S.N. Leioa Bizkaia Spain E-48080
4. University of Concepción; Concepción Chile
5. Cochrane Centre School of Medicine Universidad de Valparaiso; Interdisciplinary Centre for Health Studies CIESAL; Viña del Mar Chile
6. CIBER Epidemiología y Salud Pública (CIBERESP); Iberoamerican Cochrane Centre, Biomedical Research Institute Sant Pau (IIB Sant Pau); Sant Antoni Maria Claret 167 Pavilion 18 Barcelona Catalunya Spain 08025