1 Center for Economic and Social Studies in Health, Hospital Infantil de México Federico Gómez, Mexico City, Mexico.
2 Geriatric Epidemiology Unit, Research Department, Instituto Nacional de Geriatría, Av. Contreras 428, Col. San Jerónimo Lídice, Alcaldía Magdalena Contreras, Mexico City, Mexico. marifercave@yahoo.com.mx.
3 Epidemiological and Health Services Research Unit Aging Area, Centro Médico Nacional, Siglo XXI, Mexico City, Mexico.
4 Research Unit in Evidence-Based Medicine, Hospital Infantil de México Federico Gómez, Mexico City, Mexico.
5 Research Department, Hospital Infantil de México Federico Gómez, Mexico City, Mexico.