QUALITY-OF-LIFE - A DYNAMIC CONSTRUCT

The principle of Einstein's theory of special relativity is that an ob server of an apparently moving body cannot be sure if the body really has moved, if he/she has moved or if both events have occurred. Althou gh Einstein was discussing physical events, a similar hypothesis may a pply to quality of life. When using quality of life instruments, one p resumes that the point of reference (the observer in Einstein's terms) does not move, i.e. that an individual's attitude towards a particula r construct will remain stable. Otherwise, changes in response to part icular variables cannot be interpreted. However, attitudes are not con stant: they vary with time and experience and are modified by such psy chological phenomena as adaptation, coping, expectancy, optimism, self -control and self-concept. For example, eating problems may be extreme ly important at one point in a person's life. However, when oral disco mfort has been diagnosed as cancer and treated with surgery or radiati on, the same individual may ''objectively'' demonstrate more problems when eating, but report them as less because they have now become rela tively unimportant. Furthermore, paradoxical reports that some groups of ill individuals rate their quality of life higher than do ''healthy '' persons raise similar questions concerning between-group point of r eference differences. Investigators in the fields of organisational ma nagement, education and psychology have developed techniques such as ' 'then ratings'', saliency indicators and individualised questionnaires in attempts to quantify within-subject variability and between-group differences pertaining to point of reference; We suggest that similar methods may help us to measure change in the impact of the different i tems of quality of life instruments; In this paper, we will describe t he theories of change associated with quality of life measurement. In addition, we will present evidence suggesting that the point of refere nce does change, the reasons for this and possible solutions to the pr oblem. (C) 1997 Elsevier Science Ltd.