In 1948, the World Health Organisation declared health to be “a state of complete physical, mental and social well-being, and not merely the absence of disease” (WHO 1978). Today, any evaluation of a new treatment should include evidence of its impact on health and quality of life (Jackowski and Guyatt 2003). Quality of life is a normative concept that could mean different things to different people (Fayers and David 2000; Cella and Nowinski 2002). Within health outcome research, the concept has been compiled to focus on those aspects that are more directly affected by a health condition and facets relating to factors such as economic status or social surroundings have been excluded. This confined
concept is called “health-related quality of life” (HRQL) and it has been defined to include the perception of an individual of his or her degree of physical, psychological and social well-being and the effects that illness and treatment
have on daily life (Jette 1993; Muldoon et al. 1998; Patrick and Chiang 2000). It is considered especially important to study
HRQL in groups with chronic conditions when the goal of care is “to make the patient’s life as comfortable, functional and satisfying as possible” (Sullivan et al. 1999)