About 35 million Americans—one person in seven—have physical or mental impairments that interfere with their daily activities (National Center for Health Statistics, 1989a). The functional limitations of more than 9 million of these people are so severe that they cannot work, attend school, or maintain a household. By these two measures alone, disability ranks as the nation's largest public health problem, affecting not only individuals with disabling conditions and their immediate families, but also society at large. Many medically, socially, and economically important issues call attention to the need for developing an effective national disability prevention program. One is modern medicine's progress in prolonging life, or, more accurately, averting deaths. For example, the odds of survival for low-birthweight babies have increased steadily during the past several decades. The age-adjusted rate of deaths caused by injuries has fallen precipitously, from 57.5 deaths per 100,000 injuries in 1950 to 35.2 deaths per 100,000 injuries in 1986 (National Center for Health Statistics, 1989a). Medical victories, however, do not always translate into absolute victories. The outcome of surviving prematurity, injury, heart attack, or stroke may be disabling conditions that can result in a diminished quality of life and the need for continuing supportive services. Because assessments of the nation's health are based largely on mortality statistics, U.S. society rarely reckons with the full consequences of extending lives. As the number of people who survive life-threatening conditions increases, quality of life issues must be given fuller consideration in health and social policy decisions.
The need to intensify the search for effective strategies for disability prevention is heightened by the aging of the population. By the year 2020, people over age 65 will number 51.4 million and constitute 17.3 percent of the population, as compared with 31.7 million and 12.7 percent in 1990.
The risk of developing cardiovascular disease, rheumatoid arthritis, and many other chronic diseases increases with age, as does the likelihood of disability caused by these conditions. If these chronic conditions cannot be prevented, then the focus of medical care and support services should be on the prevention of associated conditions with the purpose of increasing the number of disability-free years in the lengthened life span.
Beyond the demonstrated need for a national disability prevention program, circumstances suggest that the beginning of the 1990s is an especially appropriate time to develop such a program. For example, two decades of efforts by disability-rights groups to increase public awareness paved the way for passage of the Americans with Disabilities Act, which bans discrimination in employment and the provision of services. This legislation affirms the goals of equal opportunity and independence for Americans with physical and mental disabilities and acknowledges the importance of their participation in the affairs of society. The act includes protection against discrimination on the basis of disability in public and private transportation, public accommodations, employment, telecommunications, and local and state government activities.
The Americans with Disabilities Act will have several beneficial effects. For example, the expected increase in the employment of people with disabling conditions should result in their enjoying higher standards of living and fuller integration into society; in addition, more individuals will have jobs commensurate with their skills and training and will receive employer-provided health benefits. Collectively, these effects should help reduce the incidence of many secondary conditions, including depression, that commonly result from discrimination and the social and economic barriers now encountered by people with disabling conditions.
Also cause for optimism in disability prevention efforts is research progress toward understanding the biological, behavioral, and environmental (physical and social) risk factors of disability. New understanding of risk factors can be translated into intervention strategies to prevent or mitigate developmental conditions, injuries, chronic diseases, and secondary conditions that increase the risk of disability. Moreover, accumulating experience shows that continuing deterioration of physical or mental health and increasing dependency need not be the outcomes of chronic diseases and functional limitations. Opportunities are increasing to reverse, interrupt, or at least slow the progression to disability, as well as to prevent the development of secondary conditions in people who already have a potentially disabling condition. A few advances in this area have been dramatic. For example, in 1990 researchers reported that administering the steroid methylprednisolone within eight hours of the occurrence of a spinal cord injury can significantly reduce the severity of resulting functional limitations (Bracken et al., 1990). Thus a person who once would have been fully paralyzed in
the legs might now retain sufficient functioning to walk with the aid of crutches and braces.
Failure to seize emerging opportunities and develop a comprehensive strategy for disability prevention is tantamount to allowing the health and quality of life of a large portion of the U.S. population to deteriorate. A growing number of health and social service professionals, policymakers, and members of the public deem such an outcome unacceptable.
In 1986, building on the work of Marge (1981), the National Council on Disability (NCD) identified and underscored the need for a national effort to prevent disability and recommended to the President and Congress that such a program be established at the Centers for Disease Control (CDC). In 1988 CDC initiated the Disabilities Prevention Program, which is designed to build capacity in disability prevention at the state and local levels, establish systems of surveillance for disabilities, use epidemiological approaches to identify risks and target interventions, and provide states with technical assistance. It is the only federal program that has been charged specifically with disability prevention. Its initial focus has been prevention of the more readily identifiable injuries and developmental disabilities, and the secondary conditions that are often associated with them.
This report, prepared by the Institute of Medicine's Committee on a National Agenda for the Prevention of Disability at the request of the CDC and the NCD, responds to the challenge to create a blueprint for a comprehensive national undertaking to reduce substantially the incidence and prevalence of disability in the United States. The report addresses many of the public health and social issues that intersect under the heading of disability. It describes a conceptual model of the characteristics and determinants of disability and outlines measures for creating a national program for disability prevention.
The remainder of this chapter describes briefly the definition and concept of disability used in this report, the application of public health concepts to disability prevention, and the report's scope and organization.
DISABILITY: DEFINITION AND CONCEPT
Although understanding of the medical, behavioral, social, and economic aspects of disability is growing, terminology continues to breed confusion, even among professionals in disability-related fields. For example, the failure of data collection agencies to use consistent definitions of disability and related concepts results in varied estimates of the prevalence of disability. Such confusion and inconsistency are common in emerging fields. Given the nascent state of disability prevention in general and of the epidemiology of disability in particular, confusion and inconsistency are understandable. But they pose obstacles to surveillance efforts and to efforts to elucidate the
many factors that underlie the disabling process and the occurrence of secondary conditions. They also impede the design and evaluation of preventive interventions. As one aspect of its work, the committee has attempted to improve conceptual clarity and sharpen the definitions of terms.
The term disability as used in this report refers to limitations in physical or mental function, caused by one or more health conditions, in carrying out socially defined tasks and roles that individuals generally are expected to be able to do (see Appendix A, this volume). The term health condition includes pathology, or active disease, as well as impairment, which refers to losses of mental, anatomical, or physiological structure or function owing to injury, active disease, or residual losses from formerly active disease. The term disabling condition refers to any physical or mental health condition that can cause disability.
Health conditions differ in the degree to which they precipitate disability, but all physical and mental health conditions that have a measurable association with or likelihood of causing disability are potentially disabling conditions. A secondary condition is any additional physical or mental health condition that occurs as a result of having a primary disabling condition. Secondary conditions quite often increase the severity of an individual's disability and are also highly preventable. An illustration of these terms applied to a hypothetical case is provided in the box below. The phrases disability prevention and prevention of disability are meant to include the prevention of potentially disabling health conditions and their progression toward disability, the prevention or reduction of disability itself, and the prevention of secondary conditions. Chapter 3 discusses these terms in greater detail in the context of a model of the disabling process developed by the committee.
AN ILLUSTRATION OF DISABILITY TERMS
Paraplegia is an example of a disabling condition. In a hypothetical scenario, a man is in an automobile crash and sustains fractured lumbar vertebrae and permanent crush-injury of the spinal cord (pathologies), which result in flaccid paralysis of the muscles of the lower limbs (paraplegia, an impairment). Consequently, he cannot walk or drive his car (functional limitations). Public transportation, sidewalks, washrooms, and work environments do not accommodate his wheelchair. As a result, he is now deprived of employment and social and cultural activities (disability). Because he is unemployed, he loses his health insurance and cannot afford to purchase an individual policy. He develops pressure sores from his wheelchair and becomes depressed (secondary conditions), which could have been prevented if he had insurance to cover appropriate educational and rehabilitative services.
In common parlance, disability is a value-laden, stereotyping term that categorizes people according to their impairments. People who have reduced ability to perform expected activities—that is, those who are said to have "disabilities"—are often viewed as permanently sick. Such a perception deprives many people with disabilities of the opportunities that should accompany their membership in society. The disability-rights and independent-living movements have struggled to overcome this stereotyping. We concur with their argument against the use of the phrase disabled people, preferring instead people with disabilities, and hasten to point out that a person's identity is the product of a host of characteristics and that disabling conditions are but a few of them. The message in this seemingly subtle preference for language is important: external factors, like stereotypes, impose obstacles to the performance of chosen roles. In fact, it is external factors like these that can transform a functional limitation into a disability.
Thus disability is not inherent in a person, nor is it determined solely by biological factors—losses or abnormalities of psychological, physiological, or anatomical structures or functions. To view disability strictly as a biological phenomenon is to categorize it as a medical entity and to ignore the complexity of factors that in combination determine whether a physical or mental impairment will progress to a functional limitation and then to disability (the inability to perform expected social and personal roles and tasks). An accurate understanding of disability requires explicit recognition of the roles of the environment and public attitudes in determining whether functional limitations become disabilities. For example, a concert pianist or a typist who loses a finger faces a more challenging rehabilitation than a computer programmer, school-teacher, or truck driver, whose work depends far less on having a full set of agile fingers.
Disability is not an unavoidable consequence of a chronic disease, an impairment, or even a functional limitation. The sophistication with which the health care system responds to an initially occurring disease, injury, or condition—in terms of medical care, assistive technology, and an array of related social support services—will affect the extent of the individual's functional limitation and the potential for progression to disability and secondary conditions. Whether disability results, and the level of severity if it does, depends on the many factors detailed in this report. These factors transcend aspects of medical care and extend to social determinants of the quality of life, including access to facilities and opportunities in everyday settings and the receptiveness of the community to persons with disabilities. Describing disability prevention in medical terms poses the danger of perpetuating the misconception that disability is purely a medical problem, confined to the domains of primary health care. Such an orientation ignores the importance of social integration and quality of life in influencing the disabling process. Major responsibility for disability prevention must rest
with society as a whole. The perceptions of the public and the willingness of society to accommodate the specific needs of people with disabilities often determine whether those individuals can carry out their chosen roles in life and be productive members of society, or whether their conditions become disabilities.
PUBLIC HEALTH AND DISABILITY PREVENTION
The public health concepts of primary, secondary, and tertiary prevention are applied to disability prevention as follows. Primary prevention seeks to avert the onset of pathologic processes by reducing susceptibility, controlling exposure to disease-causing agents, and eliminating, or at least minimizing, behaviors and environmental factors that increase the risk of disease or injury that can cause disabling conditions. Secondary prevention is the early detection of a potentially disabling condition, followed by the implementation of interventions that are designed to halt, reverse, or at least retard the progress of that condition. Secondary prevention becomes especially important as the population ages, given that the prevalence of chronic conditions increases with age as does the risk of disability associated with these conditions. Tertiary prevention concentrates on reducing the effects of an existing condition. In tertiary preventive strategies habilitative and rehabilitative measures, which include counseling, vocational training, environmental adaptations, and mobility training, are employed to restore as much functioning as possible. Tertiary measures are also intended to prevent the occurrence of secondary conditions, such as muscle atrophy, obesity, ulcers, and contracture—an area of major interest in this report.
Disability prevention measures described in this report are designed to reduce the incidence and prevalence of potentially disabling conditions in the U.S. population. The targets of these measures are high-risk groups that, because of behavioral, environmental, biologic, economic, dietary, or other factors, are more likely than the rest of the population to develop a disability. Risk factors are many and varied, and their identification is a major focus of epidemiological research, which helps to identify the often complex chain of events that can lead to disability and secondary conditions. For some disabling conditions, this chain of events begins before birth. Lack of good prenatal care beginning early in pregnancy, for example, increases the risk of prematurity and low birthweight, which in turn increases the risk of developmental disability, such as mental retardation. Because women who are socially disadvantaged and those who live in rural areas have the most difficulty obtaining obstetrical services, they are an obvious target group for preventive measures designed to increase access to and use of prenatal care.
Another example is disabilities resulting from injuries sustained in traffic
collisions. These also lend themselves to focused prevention strategies, such as seat belt laws and passive restraints, stringent drunk-driving laws and enforcement, and educational programs to encourage bicyclists to wear helmets. The obvious target population is teenagers and young adults, for whom traffic injuries are the leading cause of mortality and morbidity.
As these two examples illustrate, disabling conditions are not the products of random events. Early identification of risk factors followed by measures to eliminate or reduce them are the cornerstones of all successful prevention strategies. In this regard, disability prevention meshes well with the public health model of disease prevention, as typified by vaccination programs that immunize at-risk populations against certain infectious agents. Obviously, greater emphasis on efforts to identify risk factors across a broad range of areas and subsequently to develop intervention measures to reduce the occurrence of diseases, injuries, and other potentially disabling conditions must be a fundamental part of a national agenda for disability prevention. Clearly, there are hundreds of important health conditions that pose the risk of disability and that are, in some measure, preventable. Many of these conditions, their risk factors, and means of primary prevention have been previously addressed.1 Primary prevention strategies are also discussed in this report, but additional emphasis is placed on the needs of people who already have potentially disabling conditions, that is, secondary and tertiary prevention—a relatively unattended area of prevention.
A Life Course Perspective
One of the major goals of disability prevention is to maximize an individual's functioning, well-being, and quality of life throughout the life course. This goal incorporates the strategies of health promotion, disease prevention, and chronic illness management to prevent disability. Within a life course framework for disability prevention, the three strategies—health promotion, disease prevention, and chronic illness management—are complementary. Health
promotion helps people develop lifestyles to maintain and enhance their well-being through both community and individual measures. Disease prevention protects people from the consequences of a threat to health, such as a disease or environmental hazard (U.S. Department of Health, Education, and Welfare, 1979). Chronic illness management includes not only medical care and rehabilitation but also psychological, social, occupational, and environmental interventions to minimize or control potential disability. After the onset of a potentially disabling condition, the focus of disability prevention becomes one of retarding the progression toward disability and preventing the development of secondary conditions.
Recognizing the interactive nature of the process that can lead to disability, a life course perspective on disability prevention should address not only the factors that are directly related to health but also the other influences that determine quality of life, because good health, as well as poor health, is the result of interactions among biological, behavioral, and environmental (social and physical) factors. It is clear, for example, that inadequate housing, lack of education, and other problems that are the traditional concerns of social service agencies are also powerful influences on success or failure in preventing disability. Thus a comprehensive approach to the design and delivery of health and social services throughout the life course is an integral element of disability prevention.
SCOPE AND ORGANIZATION OF THE REPORT
In the 1985 publication Injury in America, the National Research Council and the Institute of Medicine identified death and disability caused by injury as one of the most important public health issues in the United States (National Research Council, 1985). This report expands on that effort by addressing a broader range of preventable disabling conditions and by considering approaches to ensure that people with disabling conditions have the opportunity to participate fully in society.
Injury prevention is perhaps the most developed area within the entire province of disability prevention. Yet the scope of effort in this area—in terms of surveillance and data collection, research, and the development and evaluation of interventions—is limited when compared with the magnitude of the need. In other areas of disability prevention, the disparity is even greater. Consequently, the scientific foundation on which prevention efforts must build is small. This is not to say that disability prevention efforts undertaken in these areas are not worthwhile. To the contrary, there is a great need for research and evaluation in disability prevention, and this report proposes an agenda for these activities. However, time and resources did not permit the committee to review current understanding in all areas of disability. One notable omission is mental health. In a recent analysis of
67 chronic health conditions or groups of health conditions, mental health conditions ranked as the ninth leading cause of activity limitation (LaPlante, 1989a). Moreover, depression and other mental health conditions are critically important determinants of the progression to physical disability, a point noted throughout this report. Given their importance, mental health conditions that lead to disability or that are involved in physical disability merit more in-depth study than was possible here.
In this report, the committee addresses the topic of disability prevention from general and specific perspectives, focusing most of their attention on the prevention needs of people with disabling conditions, that is, secondary and tertiary prevention. Chapter 2 describes the magnitude and dimensions of disability in the United States. Chapter 3 describes the committee's conceptual approach to disability, assesses the adequacy of existing data collection and surveillance systems for addressing this important public health issue, and describes how the tools and principles of epidemiology can be used to study health-related limitations in human activity and to develop preventive interventions.
In the four succeeding chapters, the committee concentrates on four major areas of disability: 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). In each of these chapters, the public health significance of each is assessed, current medical and social approaches to prevention are discussed, and research needs are identified.
Chapter 8 reviews government and private-sector programs concerned with disability prevention and describes and assesses the overall effectiveness of existing service programs and their guiding policies. Obstacles to and opportunities for achieving a more integrated and effective program are discussed. In the first eight chapters of the report, committee ''findings"—statements thought to be of particular importance—are printed in bold type and indented.
The concluding chapter (Chapter 9) presents the committee's overarching conclusions and recommendations. Together, they constitute a framework for assembling a national agenda for the prevention of disability. The recommendations are organized into five groups: organization and coordination of a national program for the prevention of disability, surveillance, research, access to care and preventive services, and professional and public education.
Finally, there are 3 appendixes in the report. Appendix A is a paper that was written for this committee by Saad Nagi. It describes disability concepts and offers an assessment of existing frameworks. Appendix B contains a dissenting statement from one committee member, Deborah Stone, and a response to her dissent by the other 22 members of the committee. Appendix C contains brief biographical sketches of the committee members.