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1 Introduction pain is the most common presenting complaint seen by physicians (Lawrence and McLemore, 19831. Sometimes the pain is the result of obvious injury or is associated with readily identifiable disease; at other times, it has no obvious cause or seems disproportionate to the disease or injury. Some pain disappears with healing or is self-limited, but some persists. Some disease processes, of course, cause long-lasting, severe, and even debilitating pain; but for most people, an episode of acute pain does not become chronic. Musculoskeletal conditions such as low back pain, joint pain, arthritis, and rheumatism are the leading causes of disabil- ity in people during their working years (Kelsey et al., 1979; U.S. Department of Health and Human Services, 19801. Back complaints are second only to upper respiratory conditions in accounting for work absenteeism (Rowe, 19691. Many different kinds of chronic pain can be identified. Each has its own characteristics and different effects on patients. For patients the experience of pain is also highly variable. Some people with moderate pain are severely impaired, whereas others with severe pain are able to continue functioning normally. How an individual experiences and manifests pain depends on a complex interaction among numerous physiological, psychological, social, and cultural variables, as well as on past pain experiences and how the pain has been handled by the practitioners the patient consults. Because of the considerable differences in types of pain and patients, it is inappropriate to speak of "the" chronic pain patient as if there 12

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INTRODUCTION 13 were only one type. Similarly, we do not use the term "chronic pain syndrome," as it implies a homogeneity among conditions that are actually quite dissimilar. The experience of pain is more than a simple sensory process. It is a complex perception involving higher levels of the central nervous system, emotional states, and higher order mental processes. As is true for other symptoms, people who experience pain, especially pain of Tong duration, tend to develop behavioral and psychological responses to their symptoms. It is not always possible to identify the causes of pain, how it is expressed, and its behavioral and psychological reac- tions and consequences. In common parlance, one may hear about "shirkers" (or malingerers) and other people in "real" pain. In fact, experienced clinicians believe that true malingerers are relatively rare. Further, "real" pain is an extraordinarily complicated phenom- enon. The physical and neurological disorder cannot provide a com- plete explanation for chronic pain or the patient's experience of pain. Moreover, neurological mechanisms for pain are not yet fully under- stood. For example, even in the case of the impingement of a lumbar disc into a nerve root, a condition that is associated with intense back pain for many people, neurologists cannot really explain why pain is experienced. What, then, accounts for the development of chronic pain? The concept of illness behavior, a social psychological term used to describe the responses of persons to being ill or to believing that they are ill, elucidates and provides a framework for understanding the observed differences among pain patients. Illness behavior is a process that includes a perception of one's own symptoms, an attribution of mean- ing to them (from something trivial to an ominous indicator of serious illness), and the way in which one seeks help in dealing with the symptoms. Such behavior is influenced by the person's personality and coping style and by the surrounding culture and society. The fact that such factors can be strong influences on the pain or other symptoms that people experience does not, however, make the pain any less real. Not only is pain a symptom that can cause substantial discomfort, suffering, and alterations in way of life, but as a clinical problem it is often resistant to diagnosis and treatment. For physicians, who are trained to diagnose and cure disease, pain reports that are not fully accounted for by a diagnosable disease can be frustrating. For the patient in chronic pain who visits a doctor expecting to find relief and an explanation for the pain, going away with neither can be equally frustrating. In a search for the pain's cause and for a way of relieving

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14 PAIN AND DISABILITY it, long rounds of tests, treatments, and referrals to specialists may ensue, often to no avail and sometimes compounding the problem. A breakdown in basic trust strains the doctor-patient relationship, mak- ing medical encounters increasingly difficult for both parties. In addition to its significance as a personal and clinical problem, chronic pain has become a sociopolitical and economic problem for public and private disability insurers. The Social Security Adminis- tration (SSA) is particularly concerned about how pain should be considered in the process of determining eligibility for disability benefits, especially when such pain seems disproportionate to objective medical findings (e.g., histories, physical examinations, x rays, and laboratory tests) relating to a past injury or ongoing disease process. Although recognizing that pain is ultimately a subjective experience, insurers must have criteria for determining eligibility for benefits that not only are fair but also can be replicated by multiple assessors. A serious problem is posed by having to decide how much dysfunction can be attributed to pain when the severity cannot be measured. Although medical professionals are relied on for data about disease and dysfunc- tion, the ultimate judgment about who qualifies for benefits is made by program administrators, and sometimes judges, who must assess such data in light of the applicable laws and regulations. From a sociopolitical and economic perspective, the question is how to assure benefits for all who need them, while avoiding a policy so generous that it imposes an unacceptable fiscal burden. Every society defines some categories of people who are exempt from work because of their age or infirmity. The distinction between those who are expected to work and those who need to be supported by public funds varies from program to program and from country to country. Criteria for eligibil- ity are often arbitrary, such as the age at which one becomes eligible for "old age" benefits or the point at which defective vision constitutes "legal blindness." Whereas many programs here and abroad recognize disability as partial and temporary as well as total and permanent, the SSA's definition is more stringent: "inability to engage in any substantial gainful activity by reason of a medically determinable physical or mental impairment which can be expected to result in death or has lasted or can be expected to last for a continuous period of not less than 12 months" (42 USC, 423 (~) (111. Although disability programs may set different boundaries to divide those judged disabled from those able to work, the criteria for those boundaries, even if arbitrary, must readily distinguish the two groups and be feasible to apply fairly and equitably. A society may accept conventional definitions of, for exam-

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INTRODUCTION 15 pie, "elderly" as a basis for exemption from work, but may find it considerably more difficult to judge that a medical disorder is so incapacitating that it keeps one entirely from working In the case of a symptom complaint such as pain without identifiable disease pro- cesses that fully account for it, the task can be extremely complex. Because the experience of pain is different for each person, how is it possible to assess pain and determine a severity beyond which one should not be expected to work? This is the crux of the problem for the SSA and for others who insure against disability. OVERVIEW OF THE REPORT Part I of the report describes the SSA's disability system, exploring its history, rationale, and sociopolitical context; describing program characteristics and procedures; and identifying problem areas and tensions in the way the system works. Many forces and pressures operate at every level of the system, from an individual's initial decision to apply for disability benefits, through the eligibility deter- mination process by which a claimant must show proof of disability to an agency charged with helping those in need while safeguarding public money, to the often differing viewpoints of the agency and the courts as to how disability decisions should be made. Part II provides a broad view of chronic pain and disability from the perspectives of economics and epidemiology. Chapter 5 summarizes what is known about the costs of disability and examines the relation between disability rates and features of the economy. During times of economic downturn and high unemployment, more people apply for, and receive, disability compensation. Estimates of the prevalence of chronic pain in the general population and its relation to work disability are examined in Chapter 6. Part III focuses on the patient who supers from chronic pain. Chapter 7 reviews the anatomy and neurophysiology of pain drawing primarily on studies of experimentally induced acute pain. Possible physiological mechanisms to explain chronic pain and promising directions in the area of pain measurement are explored. The experi- ence of pain, how the patient behaves in response to it, and the social and psychological pressures contributing to its development and main- tenance are discussed in Chapters 8 and 9. Issues in the clinical management, assessment, and rehabilitation of chronic pain and associated dysfunction are examined in Part IV. Chapter 10 includes a discussion of the many aspects of diagnosing and treating chronic pain and elements of the doctor-patient relationship

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16 PAIN AND DISABILITY that may be adversely affected by the often Biscuit search for a diagnosis and relief. Because pain cannot be measured directly, vari- ous indirect methods for assessing its effects on patients have been devised. Chapter 11 reviews a variety of assessment techniques and suggests ways to use them more appropriately in clinical practice and in disability determination. Although it is generally believed that early rehabilitation of pain patients would be an effective means of managing pain and limiting dysfunction, few data exist to support the idea. Various approaches to pain rehabilitation are discussed in Chapter 12. Studies of treatment outcomes, including those that explore the hypothesized effect of receipt of disability benefits on outcomes, are analyzed. Finally, Part V contains the committee's conclusions and recommen- dations. It should be noted that the committee worked from the assumption that the existing legal definition of disability for the SSA (requiring the total inability to work and implying permanent impair- ment) was so rooted in the philosophical and political issues that led to the creation of the program and that have accompanied it throughout its history (discussed in Chapter 2) that it would not be fruitful to entertain seriously recommendations for changing the definition. Fur- ther, such an endeavor would be beyond this study's scope and mandate. Within the constraints of this definition, however, many programmatic and procedural issues were considered. The committee's conclusions and recommendations (1) address ways to improve the assessment of chronic pain patients within the Social Security disabil- ity programs; (2) suggest demonstration projects to provide further information for such improvement; (3) offer views on the clinical management of patients with chronic pain; and (4) identify promising research and data collection activities that would add significantly to the existing knowledge about chronic pain, illness behavior, disability, and their interrelations. Because of its breadth, this report should interest many different audiences, including those policymakers, insurers, program adminis- trators, health care professionals, clinical researchers, and members of the public who are concerned about the nature of chronic pain and how it relates (and might better relate) to disability benefits. The detailed discussions of the nature of pain, the origins and treatment of pain, and the pathway from acute to chronic pain and then to chronic disabling pain should provide useful information to clinicians, re- searchers, and the public. This discussion is also the context for the analysis of disability policy and procedures, thereby contributing to the ongoing process of informing public policy.

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INTRODUCTION 1 7 A NOTE ABOUT DEFINITIONS Terms relating to chronic pain and resulting disability are defined and used in a number of different ways both in the literature and by disability program administrators. For example, the SSA uses the word "impairment" with two quite different meanings: an impairment is a disease, such as rheumatoid arthritis, and also the inability to do something that results from a disease. The HHS Commission on the Evaluation of Pain (U.S. Department of Health and Human Services, 19S7) defined impairment as the psychophysiological manifestation of an injury or disease. This lack of uniformity arises both from the varied disciplines concerned with these issues and from the complexity and incomplete understanding of the concepts themselves. Recognizing that there is room for disagreement, the committee chose to adopt a modified version of the World Health Organization (WHO) definitions of several key terms. These definitions are used consistently throughout this report in order to avoid misunderstanding. ~ Impairment: Any loss or abnormality of psychological, physiolog- ical, or anatomical structure or function. (This is the same as the WHO definition.) The functions that are lost or become abnormal because of chronic pain may include walking, sitting, bending over, anticipation, mem- ory, cognition, and mood. Functional limitation: Any restriction or lack of ability to perform an activity in the manner or within the range considered normal for a human being that results from an impairment. (This is the WHO definition of"disability.") This is a loss of capabilities as a result of the inability to effectively integrate purposeful functions (physical and/or psychosocial) because of pain, disease, or impairment. This Toss may include functions such as visiting family or friends, typing for hours, gardening, houseclean- ing, shelving merchandise, or operating a chain saw. Disability: A disadvantage for a given individual (resulting from an impairment or a functional limitation) that limits or prevents the fulfillment of a role that is normal (depending on age, sex, social, and cultural factors) for that individual. (This corresponds to the WHO definition of"handicap.") Disability limits or prevents fulfilling a role in life. Because of pain, a person may no longer be able to perform satisfactorily at home, school, and work and in social settings (i.e., as a father, mother, employee, student, etc.~.

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18 PAIN AND DISABILITY The committee emphasizes that patients with chronic pain are heterogeneous. Any time period used to define chronic pain is arbi- trary. The committee chose to use the terms acute pain and chronic pain as they were defined by the HHS Commission. Acute pain: Pain of recent onset and probable limited duration. Chronic pain: Pain lasting for Tong periods of time. More than 6 months is a commonly used duration. Such pain may be associated with a residual structural defect that persists long after the acute episode or pain associated with the persistence of the disease process, as in arthritis. Chronic pain may also be pain persisting past healing time without objective physical findings of residual structural defect or pain persisting past the active state of a disease process. Pain that recurs regularly and frequently over long periods of time is also considered chronic pain. As we have noted, all of these terms can and have been used differently. We try in this report to be as clear as possible. Often, we use terms such as work disability, social disability, and legal disabil- ity, as appropriate. Low back pain is used as an example throughout this report for several reasons: more clinical, epidemiological, and administrative information is available for back pain than for other types of pain; chronic musculoskeletal pain, and particularly chronic low back pain, is the most common of the "problem" cases for the SSA disability system; and the issues surrounding the assessment arid management of back pain and patients with such pain are illustrative of those of chronic pain conditions in general. This does not mean that back pain is necessarily representative of all other types of pain. REFERENCES Kelsey, J.L., White, A.A., Pastides, H., and Bisbee, G.E. The impact of musculoskeletal disorders on the population of the United States. Journal of Bone and Joint Surgery 61A:959~964, 1979. Lawrence, L., and McLemore, T. 1981 Summary: National Ambulatory Medical Care Survey. NCHS Advance Data, No. 88. U.S. Department of Health and Human Services Pub. No. (PHS)83-1250, 1983. Rowe, M.L. Low back pain in industry: a position paper. Journal of Occupational Medicine 11:161-169, 1969. United States Department of Health and Human Services. Report of the Commission' on the Evaluation of Pain. Washington, DC: U.S. Government Printing Office, 1987. United States Department of Health and Human Services. Social Security Administra- tion. Disability Survey 72. SSA Pub. No. 13-11812, 1980.