Integrating response shift into health-related quality of life research: a theoretical model

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Abstract

Patients confronted with a life-threatening or chronic disease are faced with the necessity to accommodate to their illness. An important mediator of this adaptation process is `response shift' which involves changing internal standards, values and the conceptualization of quality of life (QOL). Integrating response shift into QOL research would allow a better understanding of how QOL is affected by changes in health status and would direct the development of reliable and valid measures for assessing changes in QOL. A theoretical model is proposed to clarify and predict changes in QOL as a result of the interaction of: (a) a catalyst, referring to changes in the respondent's health status; (b) antecedents, pertaining to stable or dispositional characteristics of the individual (e.g. personality); (c) mechanisms, encompassing behavioral, cognitive, or affective processes to accommodate the changes in health status (e.g. initiating social comparisons, reordering goals); and (d) response shift, defined as changes in the meaning of one's self-evaluation of QOL resulting from changes in internal standards, values, or conceptualization. A dynamic feedback loop aimed at maintaining or improving the perception of QOL is also postulated. This model is illustrated and the underlying assumptions are discussed. Future research directions are outlined that may further the investigation of response shift, by testing specific hypotheses and predictions about the QOL domains and the clinical and psychosocial conditions that would potentiate or prevent response shift effects.

Introduction

An orthopaedic surgeon once commented that it must be difficult to study quality of life (QOL) since it not only means different things to different people, but can also mean different things to the same person over a disease trajectory. He recounts the story of a woman who, after hearing her diagnosis of osteosarcoma, told him that if her bone tumor prevented her from being able to walk, life would no longer be meaningful to her and she would prefer euthanasia. When the time came that this woman was confined to a wheelchair, she informed him that life still held value for her but that if she were to become incontinent or bedridden, then life would loose its meaning and she would prefer euthanasia. However, when the time came that she was incontinent and bedridden, the woman stated vehemently that life still held meaning for her and that she was not ready for euthanasia. This story illustrates how internal standards, values and the conceptualization of life quality can change over the course of the disease trajectory and that these changes may be inherent to the process of accommodating the illness.

This patient has undergone what is called `response shift'. The working definition of response shift, adopted in this paper, refers to a change in the meaning of one's self-evaluation of a target construct as a result of: (a) a change in the respondent's internal standards of measurement (scale recalibration, in psychometric terms); (b) a change in the respondent's values (i.e. the importance of component domains constituting the target construct); or (c) a redefinition of the target construct (i.e. reconceptualization) (see also Schwartz and Sprangers, 1999).

Whereas the previous story is anecdotal, there is ample evidence of paradoxical and counter-intuitive findings in the literature which can be interpreted in terms of response shift. For example, patients with a life-threatening disease or disability were found to report a stable QOL Andrykowski et al., 1993, Bach and Tilton, 1994. Moreover, a number of researchers have documented that people with a severe chronic illness report a level of QOL neither inferior nor better than that of less severely ill patients or healthy people Cassileth et al., 1984, Stensman, 1985, Breetvelt and Van Dam, 1991, Andrykowski et al., 1993, Groenvold et al., 1999. Additionally, health care providers and significant others tend to underestimate patients' QOL as compared to patients' evaluations of their own QOL Sprangers and Aaronson, 1992, Friedland et al., 1996, Sneeuw et al., 1996. Furthermore, cancer patients are more willing to undergo risky and toxic treatments with minimal chance of benefit than healthy people or people with a benign disease Llewellyn-Thomas et al., 1989, O'Connor, 1989, Slevin et al., 1990, indicating that patients may have lowered their standards of tolerance and/or changed their values. Perhaps most profound is the discrepancy between clinical measures of health and patients' own evaluations of their health (Daltroy, 1999; Padilla et al., 1992, Kagawa-Singer, 1993). All of these lines of evidence suggest that response shift plays an important yet not explicitly measured role in assimilating illness.

The concept of response shift has its foundation in research on educational training interventions (Howard et al., 1979b) and organizational change (Golembiewski et al., 1976). Whereas Howard and colleagues defined response shift in terms of changes in internal standards of measurement, Golembiewski and colleagues introduced the component of reconceptualization in addition to this scale recalibration. While changes in values are inherent in Golembiewski's description of reconceptualization, the working definition adopted in this paper includes this as a separate third component that is relevant to the change in the meaning of one's self-evaluation. Making it a distinct third aspect will thus highlight its importance and emphasizes the need to measure it carefully.

The extent to which the three components of response shift are distinct or interconnected is still unknown. It may be the case that these aspects of response shift are ineluctably intertwined. Alternatively, changes in internal standards, values or conceptualization may only reflect response shift when they occur in pairs. For example, changes in internal standards may only reflect response shift when they are coincident with changes in values or changes in conceptualization. The interconnection may also reflect a hierarchical nature. For example, Golembiewski and colleagues adopted the following hierarchy, where reconceptualization needs to be ruled out before changes in internal standards can be detected. This approach makes sense since changes in internal standards of measurement will have lost their meaning if the construct itself has changed over time. Conversely, it is difficult to imagine that changes in internal standards might occur without affecting the conceptualization of the construct. Thus, while clearly distinguishing the three aspects of response shift is needed to elucidate the concept, recognizing their interconnectedness is also necessary to acknowledge the complexity and richness of the phenomenon (see also Schwartz and Sprangers, 1999).

Since response shift refers to a change in the meaning of one's self-evaluation, it may occur in any field where self-reports are required (Howard et al., 1979b). The focus of this paper will be on response shifts that may take place in the area of health-related QOL, as a result of changes in health status. Integrating response shift into health-related QOL research would enhance the sensitivity and relevance of this line of research. Understanding response shift requires a sound theoretical model. In this paper, a theoretical model is proposed to clarify and predict the occurrence or absence of response shift effects and how response shift may affect perceived QOL (Fig. 1). Additionally, future research directions are outlined that may further the investigation of the response shift phenomenon, by testing specific hypotheses and predictions about the QOL domains and the clinical and psychosocial conditions that may yield response shift effects.

Section snippets

Theoretical model

The proposed model addresses how response shift may affect health-related QOL as a result of changes in health status. It has five major components: (1) a catalyst, (2) antecedents, (3) mechanisms, (4) response shift and (5) perceived QOL. The catalyst in QOL research would refer to a change in the respondent's health status, that may or may not result from a treatment. The antecedents refer to stable or dispositional characteristics of the individual. Examples of such antecedents include

Illustration

Three examples are provided to elucidate this preliminary model. Imagine three women, Jane, Ann and Mary, all of whom are diagnosed with Stage 3 breast cancer. Jane expects that she is able to control important features of her day-to-day life, and thus has a generalized expectancy of an internal locus of control. When confronted with her diagnosis, Jane would seek to maintain a sense of control. However, her focus remains on controlling disease-specific domains which are not currently within

Discussion of the model

Conceiving the proposed model as a single process would be overly simplistic and would do injustice to the complex, multifaceted, and dynamic reality of psychological adaptation to illness. Rather, the model is meant as a framework which may guide the conceptualization and measurement (Schwartz and Sprangers, 1999) of QOL over time. Additionally, this model is not new from clinical (Wilson, 1999) or theoretical perspectives. For example, it has similarities with control theory's approach to the

Future research directions

There are many aspects of this theoretical model that need to be developed in future research. The components of the model, including the catalyst, antecedents, mechanisms and perceived QOL, would benefit from investigations which highlight or identify the specific conditions which would potentiate or prevent response shifts. Regarding the catalyst, it would be important to identify what parameters of health state changes or interventions would initiate the response shift process. Parameters

Acknowledgements

We would like to acknowledge the invaluable contribution of the following social and medical scientists who participated in the Response Shift Workshop held in Boston, December 1996 and funded by AHCPR (grant No. 1 RO1 HSO8582-01A1) to Dr. Schwartz and matched by a contribution from Frontier Science and Technology Research Foundation, Inc. These participants included: Achilles A. Armenakis, Ph.D.; Katy Benjamin, S.M., M.S.W.; Lawren H. Daltroy, Ph.D. P.H.; Susan Folkman, Ph.D.; Maureen

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