Quality of life in health

 The focus on the measurement of quality of life in health research can be traced back to a historical transition from a predominantly curative focus of medical care in the first half of the 20th century to an emphasis on the side-effects of medical treatments and the impact of disease and illness on physical, social, and emotional wellbeing. This transition is exemplified in the following well-known definition of health offered by the World Health Organization (WHO): “Health is a state of complete physical, mental and social wellbeing and not merely the absence of disease or infirmity”. However, although this definition of health is widely cited as providing the impetus for the measurement of quality of life in health research, the term quality of life was initially not frequently used for the purposes of health outcomes measurement. Rather, the WHO‟s definition was first followed by studies on the relationships between health, wellbeing, life satisfaction and happiness, and, until 1985, these terms were more frequently encountered in citations indexed in PubMed (National Center for Biotechnology Information) than was the term quality of life.
 In PubMed (National Center for Biotechnology Information), most of the studies pertaining to life satifaction or wellbeing were indexed under the medical subject heading (MeSH ) “personal satisfaction,” which was defined as “the individual's experience of a sense of fulfillment of a need or want and the quality or state of being satisfied” (National Library of Medicine). The term “life satisfaction” was first used in a PubMed citation report pertaining to an influential publication by Neugarten, Havigurst, and Tobin entitled “The Measurement of Life Satisfaction,” which was published in the Journal of Gerontology. The authors specifically reported on the development of two instruments for the measurement of life satisfaction.
 The term quality of life has increasingly been used to refer to the measurement of broadly defined health outcomes. After 1985, the frequency of the term quality of life occurring in the title or abstract of citations in PubMed exceeded that of the terms life satisfaction, wellbeing, or happiness, and the term quality of life has been used in more than 1% . Thus, the use of the term quality of life to refer to the measurement of health outcomes is a fairly recent phenomenon in health research, and the initial focus that arose from the WHO definition of health was on the measurement of life satisfaction and wellbeing, and not, explicitly on the measurement of quality of life. The initial focus on life satisfaction and wellbeing continues to be reflected in the definitions of quality of life and health-related quality of life that are frequently encountered in health research publications.
 Even though the term quality of life is now widely used, there exists considerable ambiguity about its meaning. In congruence with the previously mentioned description of the medical subject heading for quality of life, the term is now generally used to refer to a wide range of broadly defined health outcomes, such as symptoms, functional status, and perceived health status, as well as global appraisals of life satisfaction, happiness, and wellbeing pertaining to life as a whole