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4 DISABILITY IN AMERICA disability have been significantly limited by the narrowness of conceptual views and inadequate data. This report gives special attention to issues related to conceptual clarity and data needs and presents a model for study- ing the progression of conditions toward disability. The disability model described in this report should facilitate the development of improved surveillance systems, an epidemiology of disability, and more effective means of pre- vention. Interfering with the development of effective prevention programs, how- ever, is the lack of an effective public health surveillance network for monitoring the incidence and prevalence of disability, including predisposing risk fac- tors. Without such a surveillance network, programs and policies intended to prevent disability will continue to be based on educated guesses rather than a solid data base that describes the sizable population of people that either have disabilities or a high risk of developing them. Furthermore, the fragmentation, gaps, and redundancies in the nation's disability-related programsâ the focus of criticism in other quarters besides this reportâwill persist. Although the current system for providing medical and social support to people with disabling conditions suffers from many inadequacies, most of the elements required for longitudinal care, as recommended by this committee, are likely to be in place. Additional financial resources may not be needed for many of the prevention measures noted here so much as a commitment to coordination, program planning, and service delivery to form a network that is readily accessible by consumer populations. TOWARD A COMPREHENSIVE APPROACH TO DISABILITY PREVENTION Despite an officially stated national goal of independence and equality of opportunity for people with disabilities, current approaches to preventing disability and improving the lives of people with disabling conditions lack conceptual clarity and unity of purpose. Reducing the prevalence and inci- dence of disability poses challenges on many fronts and requires coherent, comprehensive responses rather than the piecemeal actions that now characterize medical, rehabilitative, and social programs related to disability. In short, disability prevention requires new thinking, new collaborations among re- searchers, new relationships between agencies and organizations, both pub- lic and private, new approaches to delivering services, and new societal attitudes. In developing its framework for a national disability prevention program, the committee sought to identify issues and needs that cut across the major categories of health conditions that can result in disability. It developed a model for disability and disability prevention (see Chapter 3) based on the work of Saad Nagi and the World Health Organization, and expanded it to
SUMMARY AND RECOMMENDATIONS 5 include risk factors and quality of life. The committee then reviewed cur- rent knowledge in four major areas; developmental disabilities (Chapter 4); injury-related disabilities, specifically those related to spinal cord injury and traumatic brain injury (Chapter 5); disabilities associated with chronic diseases and^aging (Chapter 6); and secondary conditions associated with primary disabling conditions (Chapter 7). Needs and challenges specific to each category of disability are identified in the individual chapters. Time and resources did not permit a review of all areas of disability. Mental health conditions, for example, are discussed only briefly as secondary conditions and, to a lesser extent, as primary conditions. Chapter 8 discusses the obstacles to and opportunities for a comprehensive approach to disabil- ity prevention, and Chapter 9 presents the committee's recommendations for a National Agenda for the Prevention of Disability. A summary of chapters 3-7 appears below, beginning with a discussion of the committee's model and followed by the committee's recommendations for a national agenda for the prevention of disability (Chapter 9 in its entirety). A Model of Disability There are two major conceptual frameworks in the field of disability: the International Classification of Impairments, Disabilities, and Handicaps (ICIDH), and the "functional limitation," or Nagi, framework, which is not accompanied by a classification system. The ICIDH is a trial supplement to the World Health Organization's International Classification of Diseases; it has stimulated extensive discussions of disability concepts, received both positive and negative reviews in the literature, and is used widely around the world. Several European countries including France and the Netherlands have adopted the ICIDH and use it extensively in administrative systems and clinical settings. As a classification system that has received broad international sponsorship the ICIDH deserves considerable attention, and the WHO is to be commended for its efforts in developing a system that has met with such success. As has been pointed out in the literature, however, the ICIDH is neither a classifi- cation of persons nor a research tool. The original intent of the ICIDH classification system was to provide a framework to organize information about the consequences of disease. As such, it has been considered by some as an intrusion of the medical profes- sion into the social aspects of lifeâa "medicalization of disablement." The WHO is planning to revise the ICIDH in the near future, which will provide opportunities for significant improvements. Both frameworks (i.e., the ICIDH and the Nagi or functional limitation framework) have four basic concepts. In the ICIDH the four concepts are disease, impairment, disability, and handicap. In the Nagi framework, the four concepts are pathology, impairment, functional limitation, and disabil-
6 DISABILITY IN AMERICA ity. Both frameworks recognize that whether a person performs a socially expected activity depends not simply on the characteristics of the person but also on the larger context of social and physical environments. Concep- tual clarity, however, seems to be a problem with some of the classifications in the ICIDH. As discussed in the literature, some of the ICIDH classifica- tions are confusing; for example, certain social role limitations (e.g., family role, occupational role) are classified as "behavior disabilities," instead of "occupation handicaps" or "social integration handicaps." Another example cited is the distinction between "orientation handicaps" and disabilities associated with self-awareness, postural, or environmental problems. In considering the options for a conceptual framework, the committee was faced with the fact that the ICIDH includes the term "handicap" in its classification. Traditionally, handicap has meant limitations in performance, placing an individual at a disadvantage. Handicap sometimes has been used to imply an absolute limitation that does not require for its actualization any interaction with external social circumstances. In recent years, the term has fallen into disuse in the United States, primarily because people with disabling conditions consider handicap to be a negative term. Yet the shadow of "handicap" as a commonly used term hovers behind the concept of quality of life, and has the effect of reducing quality of life even though impairment, functional limitation, and disability do not necessarily do so. Much as the term "cripple" has gone out of style, handicap seems to be approaching obsolescence, at least within the community of people with disabilities in the United States. The committee concurs with those who have noted internal inconsisten- cies and a lack of clarity in the ICIDH concepts of disability and handicap, and it notes the need for its pending revision. It prefers not to use handicap in this report and offers an alternative framework that does not focus on the consequences of disease. The committee's alternative framework draws on the widespread acceptance and success of the ICIDH and the conceptual clarity and terminology of the Nagi framework, and then adds risk factors and quality of life into a model of the disabling process. Committee mem- bers found that this framework and model improved their understanding of the relationships among and between components of the disabling process and helped them identify strategic points for preventive intervention. It is hoped that this framework will be considered as a viable alternative in the revisions of the WHO ICIDH. The conceptual framework used in this report is composed of four related but distinct stages: pathology, impairment, functional limitation, and dis- ability. In the course of a chronic disorder, one stage can progress to the next. But depending on the circumstances, progressively greater loss of function need not occur, and the progression can be halted or reversed. Thus disability prevention efforts can be directed at any of the three stages
SUMMARY AND RECOMMENDATIONS PATHOLOGY â¢* IMPAIRMENT -+⢠FUNCTIONAL LIMITATION -* DISABILITY Interruption or Loss and/or Restriction or lack Inability or interference of abnormality of of ability to perform limitation in normal bodily mental, emotional, an action or activity performing socially processes or physiological, or in the manner or defined activities structures anatomical structure within the range and roles expected or function; considered normal of individuals includes all losses that results from within a social or abnormalities, impairment and physical not just those environment attributable to active pathology; also includes pain Level of reference Cells and tissues Organs and organ systems Organismâ action or activity performance (consistent with the purpose or function of the organ or organ system) Societyâ task performance within the social and cultural context Example Denervated muscle in arm due to trauma Atrophy of muscle Cannot pull with arm Change of job; can no longer swim recreationally Figure 3. An overview of the concepts of pathology, impairment, functional limita- tion, and disability. that precede disability, as well as at the disability stage itself, where efforts can focus on reversal of disability, restoration of function, or on prevention of complications (secondary conditions) that can greatly exacerbate existing limitations or lead to new ones. Figure 3 summarizes the four stages of the framework. As mentioned above, the committee's model for disability builds on the conceptual frameworks of Nagi and the WHO, placing disability within the appropriate context of health and social issues (Figure 4). It depicts the interactive effects of biological, environmental (physical and social), and lifestyle and behavioral risk factors that influence each stage of the disabling
8 DISABILITY IN AMERICA process; the relationship of the disabling process to quality of life; and the stages of the disabling process that often precede disability. A brief de- scription of the components of the model follows. Risk Factors Risk factors are biological, environmental (social and physical), and lifestyle or behavioral characteristics that are causally associated with health-related conditions. Identifying such factors can be a first step toward determining a mechanism of action in the disabling process and then developing preven- tive interventions. The disability research and service communities have not yet adopted a systematic, comprehensive conceptual model for under- standing disability risk factors. A model that incorporates biological, envi- ronmental (physical and social), and lifestyle and behavioral risk factor categories will help move the disability research and service communities nearer to a more unified understanding of disability and disability preven- tion. Quality of Life The quality of life concept subsumes many aspects of personal well- being that are not directly related to health. It is becoming increasingly clear, however, that health is the product of a complex array of factors, many of which fall outside the traditional province of health care. Similarly, the health of the nation's citizens has commercial, economic, and social importance. Thus quality of life is assuming greater importance and acceptance, and its enhancement, in addition to curing disease or improving survival, is becoming an accepted goal of the health-related professions. As depicted in Figure 4, quality of life affects and is affected by the outcomes of each stage of the disabling process. Within the disabling process, each stage interacts with an individual's quality of life. There is no universal thresholdâno particular level of impairment or functional limita- tionâat which people perceive themselves as having lost their personal autonomy and diminished the quality of their lives. Yet perceptions of personal independence and quality of life are clearly important in determin- ing how individuals respond to challenges at each of the four stages of the disabling process. Similar theoretical models for health status and quality of life have been described by others. The Disabling Process At the center of the model is the disabling process. Although it seems to indicate a unidirectional progression from pathology to impairment to functional
SUMMARY AND RECOMMENDATIONS Risk Factors Environment / \ Lifestyle and (Social and I I Behavior Physical) Figure 4. Model of disability showing the interaction of the disabling process,. quality of life, and risk factors. Three types of risk factors are included: biological (e.g., Rh type); environmental (e.g., lead paint [physical environment], access to care [social environment]); and lifestyle and behavior (e.g., tobacco consumption). Bidirectional arrows indicate the potential for "feedback." The potential for additional risk factors to affect the progression toward disability is shown between the stages of the model. These additional risk factors might include, depending on the stage of the model, diagnosis, treatment, therapy, adequacy of rehabilitation, age of onset, financial resources, expectations, and environmental barriers.
10 DISABILITY IN AMERICA limitation to disability, and although a stepwise progression often occurs, progression from one stage to another is not always the case. An individual with a disabling condition might skip over components of the model, for example, when the public's attitude toward a disfiguring impairment causes no functional limitation but imposes a disability by affecting social interac- tion. Also, the effects of specific stages in the model can be moderated by such interventions as assistive devices. Similarly, environmental modifica- tion (e.g., elimination of physical obstacles and barriers) is an important form of disability prevention, as is such landmark antidiscrimination legis- lation as the recently enacted Americans with Disabilities Act. A variety of personal, societal, and environmental factors can influence the progression of a disabling condition from pathology to disability. They can also affect the degree of limitation or disability a person experiences and the occurrence of secondary conditions. A few of these factors are health status, psychological state, socioeconomic status, educational attain- ment and vocational training, climate, and the presence of multiple conditions and disabilities. As indicated in the model, quality of life is an integral part of the disabling process. Research indicates that a person's perception of quality of life influences his or her responses to potentially disabling conditions and therefore outcomes. In turn, each successive stage in the disabling process poses an increasing threat of diminished quality of life. Measures that reduce this threatâfor example, providing assistive technology that enables an indi- vidual to remain autonomous in at least some roles or modifying the work site to accommodate a person's limitationsâcan be effective interventions for preventing disability. Thus disability is the product of a complex interactive process involving biological, behavioral, and environmental (social and physical) risk factors, and quality of life. Although disability always begins with a pathological condition, it is not inevitable even for people with incurable diseases or injury-caused conditions that carry the highest risks. There are usually, if not always, many points in the progression to disability at which to intervene and improve the quality of life for people with potentially disabling condi- tions. The next four sections briefly discuss some of the information from each of the focus chapters. In the full report, these chapters each cover the magnitude of disability related to that category of disability, data needs, and prevention strategies. Although some primary prevention measures are de- scribed and discussed, the emphasis in the chapters and in these sections is on prevention for people who already have potentially disabling conditions (i.e., secondary and tertiary prevention).
SUMMARY AND RECOMMENDATIONS 11 Developmental Disabilities Developmental disabilities affect about 4 percent of the population under age 21 and are caused by a variety of conditions, including cerebral palsy, seizure disorders, mental retardation, hearing and vision impairments, au- tism, structural birth defects (e.g., spina bifida) that cannot be corrected by surgery, and social and intellectual deprivation. These conditions, which usually persist throughout an individual's lifetime, are diagnosed in an esti- mated 80,000 children each year. Because of their early onset, developmental disabilities account for a large percentage of the cumulative total of disabil- ity years' for all age groups. In 1984, federal, state, and local governments spent an estimated $16.5 billion on programs and services for children with developmental disabilities. Not included in this cost estimate are programs and services for the additional 5-10 percent of all children who have learn- ing disorders and require special education services. Research has led to a number of important measures for preventing po- tentially disabling conditions that are acquired during childhood or that are the product of events during prenatal development. For example, lead screening followed by environmental lead abatement programs can reduce the incidence of lead toxicity. The removal of lead from gasoline has significantly reduced environmental exposure to lead. In the late 1970s an estimated 1.5 million children ages 6 months to 5 years had blood lead levels greater than or equal to 25 |J.g/dl. It has also been estimated that, in 1984, only 200,000 children (ages 6 months to 5 years) in standard metropolitan statistical areas (SMSA) had blood lead levels greater than or equal to 25 H-g/dl. Recent studies indicate, however, that adverse effects on the fetus and child prob- ably begin at blood lead levels of 15 |J.g/dl and below. A lower recommended threshold (currently 25 pig/dl) will probably be set, and more aggressive measures are being advocated for removing lead from the environment. Interventions to prevent many birth defects and developmental disabilities have not yet been developed. Even when the means are known, they are often not adopted. For example, abstinence from alcohol during pregnancy prevents fetal alcohol syndrome, which can result in mental retardation, growth deficiency, facial abnormalities, and other conditions. The prevalence of fetal alcohol syndrome in the general population is estimated to be 1.7 cases per 1,000 births, but much higher rates have been reported for certain groups. *A "disability year" is a year of life lived with a defined disability. Similar to "years of potential life lost," disability years provide an indicator of public health significance.
12 DISABILITY IN AMERICA Injury-related Disabilities About 57 million Americans sustain injuries each year at a total lifetime cost of $158 billion. For every death caused by injuriesâabout 142,000 annuallyâ16 people are hospitalized and 381 additional people incur inju- ries that do not require inpatient treatment. About $108 billion in economic costs, more than two-thirds of the total estimated lifetime cost of injuries, stem from nonfatal injuries. In this report, the committee focused on head injuries and spinal cord injuries, which can cause significant physical, neurological, and psychosocial deficits and result in economic costs per person that are among the highest for injury-caused pathologies and impairments. Each year, about 1.3 million people suffer head injuries, and 70,000 to 90,000 of these individuals sus- tain moderate to severe traumatic brain injuries. Total annual medical costs for people who sustain head injuries were estimated to be $12.5 billion in 1982. At highest risk of sustaining traumatic brain injuries are people between the ages of 15 and 24, especially males. Demographic studies indicate that the incidence of traumatic brain injury is greatest for nonwhite urban populations and lowest for white populations living in suburban and rural areas. Motor vehicle collisions and falls are the leading causes of such injury. To the extent that they are discernible, trends over the past 10 years indicate that improvements in emergency medical services and acute management of head injuries have substantially increased the proportion of people who survive these injuries. Each year, between 10,000 and 20,000 people sustain spinal cord inju- ries. Estimated lifetime costs for consequent medical treatment for such injuries range from $210,400 to $751,900, depending on the extent of injury. The most common major impairments are muscle paralysis and loss of sen- sation. Older adolescent males and young men are at greatest risk of spinal cord injury. Motor vehicle collisions and falls are the leading causes, followed by acts of violence, especially those involving firearms. In the 1950s, only people with low-level paraplegia were generally expected to survive; today, even people with high-level quadriplegia survive and live lives of high quality. A national study found that quadriplegia continues to be the outcome for half of all people who sustain spinal cord injuries; however, the proportion of people with quadriplegia who have neurologically incomplete lesions and therefore retain some motor control and sensation increased from 38 percent in 1973 to 54 percent in 1983. Disabilities Associated with Chronic Disease and Aging The prevalence of chronic diseaseâincurable, long-lasting pathologies such as osteoarthritis, cancer, heart disease, and diabetesâhas increased to near-epidemic proportions in the United States. Almost half of all working-
SUMMARY AND RECOMMENDATIONS 13 age people have one or more chronic conditions. An estimated 80 percent of the elderly have a chronic condition, and about 40 percent have some form of activity limitation due to chronic conditions. Chronic conditions increase a person's risk of disability, although the degree of risk varies among conditions. Indeed, the most prevalent condi- tions, such as sinusitis, hypertension, and hearing impairment, generally pose low risks of activity limitation, whereas the least prevalent conditions, such as multiple sclerosis and lung or bronchial cancer, pose very high risks of disability. Thus conditions that frequently result in disability may be more appropriate targets for primary prevention strategies, and those that pose lower risks of developing into disability may be more appropriately addressed by secondary or tertiary prevention strategies. Many chronic conditions are associated with the aging process, which contributes to the widely held stereotype that aging is synonymous with a decline in functional capacity. An increasing body of research contradicts this stereotype, demonstrating that the physical and mental health status of elderly people can improve as well as deteriorate. Studies show, for example, that the adoption of health-promoting practices even late in life is beneficial. Potentially debilitating problems such as those associated with incontinence and osteoporosis are amenable to skillful rehabilitation. Prospects are good for increasing the number of disability-free years in the average life span, but much more research on the aging process, on potentially effective inter- ventions, and on the delivery and coordination of services is needed. Secondary Conditions Associated with Disability People with disabling conditions are often at risk of developing second- ary conditions that can result in further deterioration in health status, func- tional capacity, and quality of life. Secondary conditions by definition are causally related to a primary disabling condition and include decubitus ulcers, contractures, physical deconditioning, cardiopulmonary conditions, and mental depression. Considerable research has been done on the etiology and prevention of certain secondary conditions (e.g., pressure sores); in general, however, secondary conditions have received very little attention from researchers and health care and social service providers, despite the causal relationship that makes many of them easily predictable. Much of what is known about the prevention of many secondary condi- tions is incidental and often results from deduction based on individual or clinical experience. There is a clear need for systematic evaluations of currently used interventions, as well as for research devoted to developing treatment protocols for people with specific types of disabilities. Such protocols would list assessment and treatment strategies for patients whose conditions matched prespecified characteristics, addressing not only medical
