In this issue of Arthritis Care & Research, Escalante and del Rincon develop a map of the disablement process in rheumatoid arthritis (1). In doing so, they bring the fruits of approximately thirty years of research on theoretical models of disability (2–8) to bear on this disease. Of particular importance, they note that disability is only the end result of a long process. That process begins with the onset of pathology (typically measured in rheumatoid arthritis [RA] by such proxies as extent of inflammation), then may move to impairment (measured by such parameters as extent of swelling or limited range of motion), functional limitation (measured by extent of mobility limitations, strength, or dexterity), before finally affecting the ability to function in more integrative activities — what we call disability.
The authors are to be commended for the rigor with which they have applied disability models to RA, but more importantly for outlining some of the important issues that arise when one puts the entire scope of RA research in the context of the process by which disability arises. Clearly, the majority of research in rheumatology, including virtually all that takes place in the basic sciences, concerns the onset and course of pathology. Just as clearly, these advances do not impart much wisdom as to why people with rheumatic diseases cease to perform activities, precisely because the factors affecting the onset and course of disease are so removed from the disability outcomes. This is the conundrum that is familiar to every clinician: some patients with apparently mild disease stop performing activities soon after onset, while others with extremely severe illness are able to get up and go about their business with only a modicum of impact. As Escalante and del Rincon state so eloquently: “… current approaches to the treatment of RA, informed by the biomedical model of disease, stress drugs and other biomedical interventions and neglect the psychosocial contributors to disease outcomes … disability in RA is explained by psychosocial factors almost to the same extent as by biomedical factors.” Others, in fact, have shown that non-biomedical factors may be more important in determining disability outcomes (9, 10).
Escalante and del Rincon also make another important contribution to the study of disability in RA by distinguishing between psychosocial factors that are intrinsic and extrinsic to the individual. Just as almost all of the research within rheumatology has focused on the pathologic end of the disability process, almost all of the research on psychosocial factors has focused on those that are inherent in the individual. Indeed, it is perhaps more than a point of semantics to observe that labeling these factors “psychosocial” may cause the reader to infer that the psychological make-up of the individual necessarily plays a central role in whether he or she will experience disability. However, what little research that has been done indicates that extrinsic factors may be even more important. For example, the social structure of the workplace has been shown to be the strongest determinant of employment outcomes in RA and other forms of musculoskeletal disease, far stronger than more traditional measures of disease severity, demographic background, or even psychological predisposition of the individual (10, 11). Adequate levels of social support, in the form of personal assistance or emotional support, appear to help individuals maintain valued life activities (12–14). At any rate, in rheumatology research as in disability research in general, precious little effort has been spent in understanding how the physical and social environments affect disability after onset of disease.
Avoiding or reducing disability remains a primary goal of patients with arthritis (15, 16). When disability occurs and valued life activities can no longer be performed, individuals appear to be at heightened risk of developing high levels of depressive symptoms (17, 18). In fact, the strong association between loss of the ability to perform some types of valued life activities and psychological distress suggests that disability theory should be extended to encompass the effects of disability on psychological well-being and quality of life.
All activities are not created equal in terms of their link to psychological well-being. The inability to perform recreational activities and/or participate in social interactions is a strong predictor of the later development of depressive symptoms (18). The economic costs attributable to depression, including the costs associated with depression in patients with musculoskeletal conditions, were estimated to be $44 billion a decade ago (19). Depression also exerts a negative influence on health in diverse ways, including increasing the risk of physical decline, poor treatment adherence, and mortality (20–22). Work disability is also linked to psychological distress (23), in addition to having substantial social costs. Work disability among persons with all forms of musculoskeletal conditions has been estimated to cost over $90 billion a year, while work disability among patients with various forms of arthritis has been estimated to cost over $64 billion a year (24). Unfortunately, total cessation of employment rather than attenuated employment is the norm. As a result, all of the work loss costs associated with musculoskeletal conditions occur among those who have stopped working; persons with these conditions who remain employed do not lose income relative to similar persons without them (24).
With this work, Escalante and del Rincon join a long list of disability theorists with strong ties to rheumatologic research (7–10). It should not be surprising that these ties exist: musculoskeletal conditions in general and various forms of arthritis in particular are associated with high rates of activity limitation (25). Indeed, all forms of arthritis are the most common condition associated with activity limitation for men and women from middle age onward (8). Moreover, although we now recognize that certain rheumatic conditions are associated with elevated rates of mortality (26), disability, especially long-term disability, remains the norm for patients with these conditions and a far more common outcome. Individuals with rheumatoid arthritis are at particular risk of disability. Compared to subjects matched for age, sex, and area of residence, persons with RA experience a greater number of losses in almost every major domain of human activity compared to persons without RA (27, 28). Work disability is a very frequent outcome in RA, with as many as 50% of persons with this condition stopping work within the first decade after disease onset, and 90% leaving work prior to normal retirement age (29). Other activity domains in which substantial activity losses have been observed over a relatively short (five-year) period are social, leisure, and service activities (30).
With disability rates so high among patients with RA, it makes perfect sense that Escalante and del Rincon have chosen to bring disability theory to RA research. In doing so, they challenge us to seek to redress disability in RA by intervening in those factors with the strongest impact on the performance of activities; that is, by finding out why impairment begets limitation, and limitation begets activity loss, and by finding out the extent to which it makes better sense to alter the environment rather than factors inherent in the individual. The answer to the latter question is likely to change over time. Medical and surgical treatments of RA are certainly more efficacious than in the past and may affect the disability process more than those formerly available. Emerging therapies may prove even more effective than those currently available. If so, it may make more sense to intervene in the pathophysiology of the RA than it now does to alleviate disability (it goes without saying that there are other reasons to use new, effective treatments). Nevertheless, the weight of the currently available evidence suggests that the return from research on the impact of altering the environment is likely to be substantial.
Previous research also challenges us to find ways to address the potential psychological distress that may be the result of disability. One way is to try to minimize disability, or avoid it when possible. Another point of intervention is available after disability occurs, when individuals are trying to cope with the activity losses that they may experience. Support for those coping efforts might take the form of providing psychological counseling, assisting in finding new activities to substitute for ones that can no longer be performed, providing assistive devices, helping individuals find assistance, or helping them marshal emotional support from friends and family members.
Each of these challenges is outside the realm of biomedical research in rheumatology/immunology in which the majority of research dollars are spent, yet have great potential to improve the physical functioning and psychological well being of patients with arthritis. Whether such research will be funded at an adequate level to produce answers to some of these questions raised by disability research remains to be seen.