Conceptual Issues in Defining Work Disability1
This chapter discusses the meaning of the term “disability” and the relationship between the generic concept of disability and the term “work disability.” The meaning assigned to these terms depends on the uses to be made of the concepts. As indicated in Chapter 1, the primary concern of the present study is with disability as used in the Social Security Administration (SSA) disability programs—the inability to engage in any substantial gainful activity because of physical or mental impairments that are medically determinable. However, in order to place the concept of work disability in perspective, first, definitions of disability are examined in a wider context.
CONCEPTS OF DISABILITY AND WORK DISABILITY
Defining disability has occupied the attention of many individuals and groups in the United States for many years. The problem of defining disability to determine eligibility for income maintenance, the perspective of the SSA, may be viewed in the context of the researchers and scholars who have considered this question in different cultures and in different
Much of the information in this chapter is drawn from the background paper “Conceptual Issues in the Measurement of Work Disability,” commissioned by the committee from Alan Jette and Elizabeth Badley for its Workshop on Survey Measurement of Work Disability held in 1999. The committee appreciates their contribution. The full text of the paper can be found in the workshop report (IOM, 2000) and is reproduced in Part II of this report.
contexts. Considerable conceptual controversy exists, growing out of different traditions that have generated several major disability frameworks found in contemporary literature. Processes of social change—including, for example, civil rights movements and development of assistive technology—have contributed to the emergence of varied, even competing, frameworks. Nonetheless, across the several different schools of thought, one can identify scholarly consensus on what constitutes the phenomenon of disability, which is the first step to achieving a common language.
How a society defines and treats persons with a limitation in ability or disability has roots in many different cultures. Contemporary Western thought can be traced to functionalism as expressed in Talcott Parsons’ definition of illness as “a state of disturbance in the normal functioning of the total human individual including both the state of the organism as a biological system, and of his personal and social adjustments” (Parsons, 1951, p. 431). This sociological perspective was the basis for definitions of disability focusing on functional status for many decades, resulting in an emphasis on the individual and individual adjustment with less attention to the extrinsic or environmental factors that influence a person’s ability to work or engage in meaningful activity. The Americans with Disabilities Act (ADA), for example, defines the term disability “with respect to an individual—(A) a physical or mental impairment that substantially limits one or more of the major life activities of such individual; (B) a record of such an impairment; or (C) being regarded as having such an impairment” (ADA, 2001).
Researchers have attempted to define disability by designing models that document the process of becoming disabled. Some of these models include: the Functional Limitation Paradigm (Nagi, 1965, 1979); the International Classification of Impairments, Disabilities, and Handicaps (ICIDH) (WHO, 1980), recently revised and renamed the International Classification of Functioning, Disability and Health (ICF); the Institute of Medicine (IOM) models (IOM, 1991, 1997b); and variations from other authors in many different contexts (Patrick and Peach, 1989; Verbrugge and Jette, 1994). While each of these models suggests a theoretical definition of disability, none offers a detailed operational definition, although the extensive classification system of the ICF permits multiple coding for individuals.
Scholarly definitions differ among themselves, but they share one thing in common. As long as they are confined to the abstract, theoretical level, they are free to add to, subtract from, or modify any of their terms and conditions, subject only to canons of logic and the scholar’s considered judgment. However, once the definitions are applied under real-world conditions, they necessarily operate under constraints of one sort or another, leading to numerous definitions used in public laws and pri-
vate contracts offering different kinds of benefits or services or in a survey context to measure inability to undertake major activities of daily living. No single definition is feasible or desirable that will fit all purposes of assessment.
Consider the main purposes to which definitions of disability are applied. A major purpose of most relevance to this report is eligibility for cash benefit programs such as Social Security Disability Insurance (SSDI) and Supplemental Security Income (SSI). Under these programs, the definition is used as a screening device. People who meet the definition receive the benefit, while those who fail to meet the definition are denied access to the benefit. The immediate and obvious constraint is that the screening of candidates for access to the benefit involves costs in terms of time of both applicants and screeners. The nature and type of these constraints under which the administering agency chooses to operate will depend on the value of the benefit that is being offered and the number of applicants. For example, the situation is obviously quite different comparing the benefits offered to applicants for a handicapped parking program and for the Social Security disability programs. No doubt the handicapped parking space is valuable to the applicant, but its value surely pales in comparison to that of income maintenance that may last a lifetime.
The monetary value of the benefit is relevant, but the resources available to screen the applicants are also important. In the Social Security disability programs, the benefits are quite valuable, whereas the resources devoted to screening applicants are limited in relationship to the demand for benefits. As the statutory definition makes clear, a person is considered “work disabled” based on the existence of a medical impairment or injury that precludes substantial gainful activity (SGA). With millions of applicants each year, SSA has to resort to administrative shortcuts in making decisions. Consequently SSA uses Listings of Impairments (Listings) as a critical early decision step to award or deny benefits. These Listings consist of medical evidence of more than 100 conditions that are considered to be of such severity that the condition can be presumed to constitute work disability regardless of the individual’s age, education, previous occupation, or other relevant factors.
Similar problems can be seen in the administration of other benefit programs such as workers’ compensation. In that state program, various states use different methods to judge eligibility for benefits. One benefit found in most of the state jurisdictions is for a permanent partial disability. An example of this is the American Medical Association Guides to the Evaluation of Permanent Impairment (AMA, 1993), which is a standardized system for translating the extent of an injury of a body part into a percentage of disability of the whole person. This type of system has been used for the assessment of compensation payments, including
workers’ compensation. Such a benefit is paid to a worker who is left with a partial disability after an accident or exposure to an occupational illness. Some states make these awards on the basis of a demonstrated actual wage loss that occurs because of the effects of the injury or as a sequel to the injury or exposure.
Other jurisdictions make these awards on the basis of the identifiable medical impairment or loss of limb, while still others make their decisions on the basis of what they term “loss of wage-earning capacity.” Essentially the latter concept uses the evaluation of the impairments and then modifies them according to the age and occupation of the worker. In spite of these differences, the theoretical basis for the awards is the same in all jurisdictions (Berkowitz and Burton, 1987). The awards are made because of the economic losses suffered by the worker by reason of the partial inability to participate in the labor force. The methods of evaluating these losses differ as each state seeks some method of approximating the concept in an administratively feasible manner in these large benefit programs. SSA faces the same necessity to find some easily understood method of making decisions in its disability programs.
In addition to benefit programs, the other main purpose of disability definitions that is most relevant to this report is in the field of surveys that have their own space and time constraints. The broad conceptual definitions are necessarily shortened, and particular portions emphasized, as survey personnel seek to fit their questions into the prescribed few lines or few minutes of time.
Recognizing these real-world constraints does not diminish the importance of the theoretical abstract concepts on which the survey or benefit definitions are based. It is the theory that gives us the objectives to which the program strives. Whether disability is a purely medical concept that can be decided by examining an individual or whether it is a relational concept is an issue that first must be explored on a theoretical level. The process of applying these concepts for providing benefits or conducting a survey may obscure the theoretical foundations, but they are surely present.
MAJOR SCHOOLS OF THOUGHT
Several schools of thought have defined disability and related concepts. Jette and Badley’s paper “Conceptual Issues in the Measurement of Work Disability” (IOM, 2000) examines in detail the different concepts or definitions including those set forth by Nagi, the World Health Organization (WHO), the IOM, Verbrugge and Jette, and others. This chapter highlights some of the key points made in that paper. As discussed by Jette
and Badley, the major differences in these frameworks lie more in the terms used to describe disability and related concepts, and in the placing of the boundaries between these concepts, than in their fundamental content. Both Nagi’s Disablement Model and WHO’s ICIDH frameworks have in common the view that overall disablement represents a series of related concepts that describe the consequences or impact of a health condition, in an interaction with a person’s environment, on the person, on the person’s activities, and on the wider participation of that person in society. After reviewing terms within each framework, the two major models along with their major derivatives can be compared and contrasted and their relationships more generally to the concept of work disability can be explored.
According to the conceptual framework of disability developed by sociologist Saad Nagi (1965), disability is the expression of a physical or a mental limitation in a social context. In striking contrast to the SSA’s definition of work disability as inability to work as a consequence of a physical or mental impairment, Nagi specifically views the concept of disability as representing the gap between a person’s capabilities and the demands created by the social and physical environment (Nagi, 1965, 1976, 1991). This is a fundamental distinction of critical importance to scholarly discussion and research related to disability phenomena.
According to Nagi’s own words:
Disability is a limitation in performing socially defined roles and tasks expected of an individual within a sociocultural and physical environment. These roles and tasks are organized in spheres of life activities such as those of the family or other interpersonal relations; work, employment, and other economic pursuits; and education, recreation, and self-care. Not all impairments or functional limitations precipitate disability, and similar patterns of disability may result from different types of impairments and limitations in function. Furthermore, identical types of impairments and similar functional limitations may result in different patterns of disability. Several other factors contribute to shaping the dimensions and severity of disability. These include (a) the individual’s definition of the situation and reactions, which at times compound the limitations; (b) the definition of the situation by others, and their reactions and expectations—especially those who are significant in the lives of the person with the disabling condition (e.g., family members, friends and associates, employers and co-workers, and organizations and professions that provide services and benefits); and (c) characteristics of the environment and the degree to which it is free from, or encumbered with, physical and sociocultural barriers. (Nagi, 1991, p. 315)
Nagi’s definition stipulates that a disability may or may not result from the interaction of an individual’s physical or mental limitations with the social and physical factors in the individual’s environment. Consistent with Nagi’s concept of disability, an individual’s physical and mental limitations would not invariably lead to work disability. Not all physical or mental conditions would precipitate a work disability, and similar patterns of work disability may result from different types of health conditions. Furthermore, identical physical and mental limitations may result in different patterns of work disability.
Nagi’s Disablement Model has its origins in Functionalism identified most closely with Talcott Parsons (1951). In the early 1960s, as part of a study of decision making in the SSDI program, Nagi (1964) constructed a framework that differentiated from three other distinct yet interrelated concepts: active pathology, impairment, and functional limitation. This conceptual framework has come to be referred to as Nagi’s Disablement Model.
In their work on the disablement process, Verbrugge and Jette (1994) maintained the basic Nagi concepts and his original definitions. Within the dimension of disability however, they categorized subdimensions of social roles that can be considered under Nagi’s concept of disability. Some of the most commonly applied dimensions include activities of daily living, instrumental activities of daily living, paid and unpaid role activities, social activities, and leisure activities. Within their framework, work disability is clearly delineated as a specific subdimension under the concept of disability.
A further elaboration of Nagi’s conceptual view of the term disability is contained in Disability in America (IOM, 1991) and in a more recent IOM revision of the disablement model highlighted in a report titled Enabling America: Assessing The Role of Rehabilitation Science and Engineering (IOM, 1997b). The 1991 IOM report uses the original main disablement pathways put forth by Nagi with minor modification of his original definitions. That report makes two important additions to the Disablement Model: the concepts of “secondary conditions” and “quality of life.” In 1997, in an effort to emphasize that disability is not inherent in the individual (as defined by SSA) but rather is a product of the interaction of the individual with the environment, the IOM issued the second report, Enabling America, where it referred to disablement as “the enabling–disabling process.” This effort was an explicit attempt to acknowledge within the disablement framework itself that disabling conditions not only develop and progress but can be reversed through the application of rehabilitation and other forms of explicit intervention.
The ICIDH, now revised and renamed the International Classification of Functioning, Disability and Health (WHO, 2001), has moved away
from a “consequence of disease” classification (WHO, 1980) to a “components of health” classification that includes a list of environmental factors that describe the context in which individuals live. Components of functioning and disability include the body component, the activities and participation component, and contextual factors, including a list of environmental factors and personal factors. A person’s functioning and disability are conceived as dynamic interaction between health conditions and contextual factors. The basic construct of environmental factors is the facilitating or hindering impact of features of the physical, social, and attitudinal world.
Concept of Social Roles
Social roles, such as being a parent, a construction worker, or a university professor, are basically organized according to how individuals participate in a social system. According to Parsons, “… role is the organized system of participation of an individual in a social system” (Parsons, 1958, p. 316). Tasks are specific activities through which the individual carries out his or her social roles. Social roles are made up of many different tasks, which may be modifiable and interchangeable. Some social roles are more flexible than others; that is, there is greater societal acceptance for modifying and interchanging tasks in some roles than others.
Fundamental to differentiating the concept of disability from those of pathology, impairment, and functional limitation is consideration of the difference between concepts of attributes or properties on the one hand and relational concepts on the other (Cohen, 1957).
To take the example of limitation in the performance of one’s work role, work disability typically begins with the onset of one or more health conditions that may limit the individual’s performance in specific tasks through which an individual would typically perform his or her job. The onset of a specific health condition—for example, a stroke or a back injury—may or may not lead to actual limitation in performing the work role—a work disability. The development of work disability will depend, in part, on the extent to which the health condition limits the individual’s ability to perform specific tasks that are part of one’s occupation, and alternatively, the degree of work disability may depend on external factors, for example, workplace attitudes, such as flexible working hours, that may restrict employment opportunities for persons with specific health-related limitations. Work disability also might be affected by accessible modes of transportation to the workplace, environmental barriers in the workplace, or willingness to modify the individual workstation to accommodate a health condition. Viewed from the perspective of role perfor-
mance, the degree of work disability could be reduced by improving the individual’s capacity to accomplish functional activities (a very traditional view of rehabilitation) or by manipulating the physical or social environment in which work occurs.
The fundamental conceptual issue of concern is that a health-related restriction in work participation may not be solely or even primarily related to the health condition itself or its severity. In other words, although the presence of a health condition is a prerequisite, “work disability” may be caused by factors external to the health condition’s impact on the structure and functioning of a person’s body or the person’s accomplishment of a range of activities.
The Dynamic Nature of Disability
The earliest disablement models represented by Nagi (1965) and the ICIDH-1 formulation (WHO, 1980) presented the disablement process as more or less a simple linear progression of response to illness or consequence of disease. One consequence of this traditional view is that disabling conditions have been viewed as static entities (Marge, 1988). This traditional, early view of disablement failed to recognize that disablement is more often a dynamic process that can fluctuate in breadth and severity across the life course. It is anything but static or unidirectional.
More recent disablement formulations or elaborations of earlier models have explicitly acknowledged that the disablement process is far more complex (IOM, 1991, 1997b; Verbrugge and Jette, 1994; Badley, 1995; WHO, 1997, 2001; Fougeyrollas, 1998). These more recent studies note that a given disablement process may lead to further downward spiraling consequences. IOM (1991) uses the term secondary conditions to describe any type of secondary consequence of a primary disabling condition. IOM (1991) also included quality of life in the conceptual model, although little attention was given to how to define this concept or make it operational for persons with disabilities. Patrick (1997), in rethinking preventive interventions for people with disabilities, focused on opportunity as the intersection between the total environment and the disabling process and defined opportunity as the four goals of the ADA, including economic self-sufficiency and full participation, which are highly related to work. Quality of life is viewed as people’s perceptions of their position in life in the context of culture and personal goals and expectations. Quality of life is the final outcome and is influenced by all aspects of the total environment, experience with health care, the disabling process, and level of opportunity.
The Concept of Work Environment
The social context for disability assessment concepts is implied in most schools of thought. The social context for SSA is the work environment. Establishing whether a person is capable of performing past relevant work or any type of substantial gainful activity in the national economy is part of the disability decision process. SSA has been using the Department of Labor’s (DOL’s) Dictionary of Occupational Titles (DOT) and selected characteristics of occupations as a basis for defining the work environment. SSA plans to replace the DOT as a description of work environment with the Occupational Information Network (O*NET) database of work requirements that is being developed by the DOL. (DOT and O*NET are discussed further in Chapter 6.) The importance of these descriptions is the interaction between the concept of an individual’s impairment and the requirements of work as influencing the ability to work in the national economy.
Relating Definitional Issues to the Measurement of Work Disability
The underlying structure of models of disablement, as discussed above, maps a pathway between a health condition or injury and the ensuing work disability. Close inspection of the definitions given above suggests that a number of steps can be identified in the pathway between the health condition and the social consequences described as work disability. At a micro level there are pathological changes in the body and impairment in the structure and functioning of organs and body systems. There may be an impact on the activity of the person, ranging from simple movements, to basic activities of daily living, to instrumental activities of daily living, and so on. These then can contribute to the individual’s capacity to perform more complex social roles, and ultimately the person’s participation in all aspects of society can be adversely affected. Work is one such social role.
As indicated earlier, work disability is a function of whether the person can perform specific work-related tasks and of external factors. From the point of view of the measurement of work disability, it may be useful to distinguish between the degree of difficulty a person may have in carrying out an activity and the other factors (such as barriers in the environment, attitudes of employers or coworkers, and other restrictions) that might prevent the performance of that activity in daily life. In this way, the levels of impact described within the conceptual models are of importance because they allow us to locate where many of the current types of assessment of work disability might fit in.
Discrete or Continuous Phenomena
Disability is commonly presented as an all or nothing phenomenon, either a person “is disabled or not.” In reality, disability in particular roles or activities is usually encountered in terms of degree of difficulty, limitation, or dependence, ranging from slight to severe. The question then becomes: Where on the disability spectrum is the threshold that determines whether a person has a disability or work disability? The question needs to take into account any assistive devices or accommodations that the person may have. In the current context, work participation is often determined as being an end point, in that people either have a work disability or they do not. In reality, the situation is likely to be more complex. For example, many people with functional and activity limitations may continue to work, but their labor force participation may be compromised in some way by the condition, including the opportunity to work. To the extent that it is, these people might be said to have some degree of work disability. In measuring work disability, a clear definition of the threshold used needs to be made.
Duration or Chronicity
There is a pervasive assumption that work disability is a long-term state. Stereotypes about disability are dominated by the archetype of a person who uses a wheelchair. Embedded in this is the notion of some disabling event, a period of adjustment and rehabilitation, and then the resumption of as full a life as possible with the assistance of any necessary assistive devices or accommodations. With much impairment, the reality of disability is somewhat different. The majority of individuals in the working age population with long-term activity restriction report that this restriction is due to musculoskeletal, circulatory, or respiratory disorders (LaPlante et al., 1996). These conditions may also be associated with varying degrees of “illness,” so that it is not just an issue of physical performance. Other considerations are pain, fatigue, and other symptoms. Many of these conditions are episodic in nature and may have trajectories of either deterioration or recovery (the latter being less common). Apart from any environment barriers or facilitators, the day-to-day or month-to-month experience of disability may be variable and may need to be taken into account in any measurement scheme.
In summary, researchers have attempted to define disability by designing models (or paradigms) that document the process of becoming disabled. While each of these models suggests a theoretical definition of disability, none offers a detailed operational definition. All definitions agree, however, in viewing disability as an intersection between the indi-
vidual intrinsic situation and the external environment that places demands and provides opportunities for individuals with disabilities.
Due to the necessity for finding some economical administrative methods of deciding eligibility in this mass production benefit program, in the majority of applications an adult is considered work disabled based solely on the existence of a medical impairment or injury that is presumed to preclude SGA. The foundation of the current work disability determination process, however, rests on medical evidence of more than 100 medical conditions (organized into Listings of Medical Impairments) that are considered to be of such severity that the condition can be presumed to constitute work disability. The determination process generally does not take into explicit account the relation of the individual within the work context.
The problem with this approach with regard to the definition and determination of work disability, as indicated by the above discussion of disability concepts and frameworks, is that a one-to-one relationship is unlikely between the presence of medical conditions and the resultant impairments and subsequent disability in substantial gainful employment. The presumption within the current SSA determination process that work disability is a direct reflection of the severity of the person’s medical condition and/or resultant impairment may have outlived its usefulness. In light of the ADA, medical advances, and new developments in technology, more attention needs to be paid to the environment, particularly in the context of work disability and vocational rehabilitation.
The committee recognizes the administrative difficulties that might be involved and that such attention may require drastic shifts in the orientation of the Social Security disability programs. Primary attention may have to shift to ways to influence the environment in which the applicant might work and to “return to work” activities. In the face of these challenges in incorporating contemporary concepts of disablement that include the dynamic nature of work, functioning, and health, SSA should undertake research focused on the relationship between the individual and the work environment and the evaluation of vocational factors as they affect work disability.
Recommendation 3-1: The committee recommends that the Social Security Administration develop systematic approaches to incorporate economic, social, and physical environmental factors in the disability determination process by conducting research on
the dynamic nature of disability;
the relationship between the physical environment and social environment and work disability; and
understanding the external factors affecting the development of work disability.
If such research is fruitful, incorporating such changes in the Social Security disability determination process will begin to move it away from a predominantly medically driven approach to consider factors beyond physical, sensory, cognitive, or emotional impairments and may ultimately involve changes in SSA’s implementing regulations.
As this chapter has shown, a full understanding of work disability needs to take into account the individual’s circumstances and the social and physical environment of the workplace. The research challenge is to apply the insights provided by the current models of disability to come to a common understanding of work disability concepts, and to understand the dynamics of the pathway between health conditions and work disability. Researchers need to find ways to incorporate an understanding of external factors influencing the development of work disability into future measurement strategies.