1. 1) United Nations, Department of Economic and Social Affairs: Population Division. World population prospects: the 2017 revision, key findings and advance tables. [Internet] Working Paper No. ESA/P/WP/248. 2017. Available from: https://esa.un.org/unpd/wpp/publications/files/wpp2017_keyfindings.pdf.
2. 2) Fundación General CSIC: Investigación sobre envejecimiento. [internet] 2016[cited 2018 May 30]; Available from: http://envejecimiento.csic.es/documentos/documentos/Informeinvestigacionenvejecimiento2017.pdf.
3. 3) Elsner B: Systematic reviews for informing clinical practice. Physiother Res Int. 2018; 23.
4. 4) Snell K, Hassan A, et al.: Types and quality of physical therapy research publications: has there been a change in the past decade? Physiother Can. 2014; 66: 382-391.
5. 5) Fernández JL, Parapar C, et al.: El envejecimiento de la población. Cuadernos de la Fundación General CSIC, LYCHNOS [Internet] 2010; 2: 1-90.