Why is age-appropriate a subjective term

Health-related quality of life

Literature:

Barthel, D. et al. (2017). The validation of a computer-adaptive test (CAT) for assessing health-related quality of life in children and adolescents in a clinical sample: Study design, methods and first results of the Kids-CAT study. Quality of Life Research, 26(5), pp. 1105-1117. doi: 10.1007 / s11136-016-1437-9.
Ellert, U. & Kurth, B.-M. (2013). Health-related quality of life among adults in Germany. Results of the study on adult health in Germany (DEGS1). Federal Health Gazette - Health Research - Health Protection, 56, Pp. 643-649. doi: 10.1007 / s00103-013-1700-y.
Morfeld, M., Kirchberger, I. & Bullinger, M. (2011). SF-36. Health questionnaire - German version of the Short Form-36 Health Survey. 2nd edition, Göttingen: Hogrefe.
Ravens-Sieberer, U. & Bullinger, M. (1998). Assessing health-related quality of life in chronically ill children with the German KINDL: First psychometric and content analytical results. Quality of Life Research, 7(5), pp. 399-407.
Ravens-Sieberer, U. & The KIDSCREEN Group Europe (2006). The KIDSCREEN questionnaires: Quality of life questionnaires for children and adolescents. Handbook. Lengerich: Pabst Science Publishers.
Robert Koch Institute (2018). KiGGS - Study on the Health of Children and Adolescents in Germany. Accessed on July 23, 2019 at www.kiggs-studie.de/deutsch/home.html.
The DISABKIDS Group Europe (2006). The DISABKIDS questionnaires for children with chronic conditions. Lengerich: Pope Science Publishers.
Ware, J. E. Jr. & Sherbourne, C. D (1992). The MOS 36-Item short-form health survey (SF-36): I. Conceptual framework and item selection. Medical Care, Jan.(6), pp. 473-483.
WHOQOL Group (1995). The World Health Organization quality of life assessment (WHOQOL): Position paper from the World Health Organization. Social Science & Medicine, 41(10), pp. 1403-1409.

Further sources:

International Society for Quality of Life Research - ISOQOL (2019). Accessed on July 23, 2019 at www.isoqol.org.
Mapi Research Trust (2019). PROQOLID [patient-reported outcome and quality of life instruments database]. Accessed on July 23, 2019 at https://eprovide.mapi-trust.org/about/about-proqolid.
RAND Corporation (1994-2019). 36-Item Short Form Survey (SF-36). Accessed on July 23, 2019 at www.rand.org/health-care/surveys_tools/mos/36-item-short-form.html.
Ravens-Sieberer, U. (2013). Kids-CAT study on the well-being of children and adolescents. Accessed on July 23, 2019 at www.kids-cat.org.
Ravens-Sieberer, U. (2011). KIDSCREEN - recording the health-related quality of life of children and adolescents by means of self-assessment and external judgment. Accessed on July 23, 2019 at www.kidscreen.org.
Ravens-Sieberer, U. & Bullinger, M. (1998). KINDL R. Revised questionnaire for CHILDREN and adolescents for recording health-related quality of life. Accessed on July 23, 2019 at www.kindl.org.
Ravens-Sieberer, U., Klasen, F., Bichmann, H., Otto, C., Quitmann, J. & Bullinger, M. (2013). Recording the health-related quality of life of children and adolescents. [Assessment of health-related quality of life in children and adolescents]. Healthcare, 75(10), 667-678. doi: 10.1055 / s-0033-1349555.
Robert Koch Institute (undated). Health in Germany up-to-date. Accessed on July 23, 2019 at www.geda-studie.de/deutsch/home.html.
Robert Koch Institute (undated). Study on the health of adults in Germany. Accessed on July 23, 2019 at www.degs-studie.de/deutsch/home.html.
Schumacher, J., Klaiberg, A. & Brähler, E. (2003). Diagnostics of quality of life and well-being - an introduction. In: J. Schumacher, A. Klaiberg & E. Brähler (Eds.). Diagnostic procedures for quality of life and well-being. Göttingen: Hogrefe.
Springer Nature Switzerland AG (undated). Quality of life research - An international journal of quality of life aspects of treatment, care and rehabilitation - An official journal of the International Society of Quality of Life Research. Accessed on July 23, 2019 at https://link.springer.com/journal/11136.
The DISABKIDS Group (2018). DISABKIDS [The DISABKIDS project and questionnaires on health-related quality of life in chronically ill children]. Accessed on July 23, 2019 at www.disabkids.org.

References:

Quality of life - a concept of individual and social welfare

We would like to thank Ms. Bärbel Kurth for her active collaboration on earlier versions of this guiding principle.