According to the 2011 World Report on Disability, approximately 1 billion people worldwide live with disability.¹ The U.S. Census Bureau puts the number of Americans with disabilities at roughly 57 million or about 19% of the population.² Both in the United States and around the globe, persons with disabilities are much more likely than others to experience significant disadvantages in education, employment, income, housing, and transportation, as well as other eco-social determinants of health.^1,3 In addition, people with disabilities often experience disparities in their health care, for example, receiving fewer screening and preventive services than do persons without disabilities. People with disabilities are more likely to experience inactivity, putting them at higher risk of chronic diseases. On average, individuals with disabilities are much more likely to report fair or poor health than are nondisabled persons.

Disabilities are diverse in their causes, nature, timing, pace, and personal and social implications. Some are congenital, others acquired. Some arrive suddenly with injury or accident; others progress slowly over time. Some gradually limit but do not threaten life; others hasten death. Some are visible to outsiders; others remain hidden. Some engender stigmatization and blame; others prompt pity and paternalism. Some are seen primarily as “diseases” (e.g., end-stage cancer, emphysema, schizophrenia), even when profoundly disabling. Anyone can become disabled, and in the fullness of time, most people do.

Given this diversity, speaking of “persons with disabilities” as a single subpopulation is almost meaningless. Even within categories of impairments—such as lower extremity mobility difficulties—the causes, manifestations, and clinical implications are wide ranging. This chapter does not discuss specific medical conditions that cause disabilities. Instead, it offers an overview of the key social and health policy issues and selected major practice concerns raised by disability, focusing on persons with disabilities related to seeing, hearing, and walking. For convenience, this chapter uses the term “disability” when referring to sensory or physical impairments. Nonetheless, it makes no presumption that individuals with these conditions are, in fact, disabled, however they choose to define the word. People with other potentially disabling conditions, such as serious and persistent mental illness or developmental disability, might require somewhat different assessments or accommodations than those described later.

Identifying individuals as disabled is complex, with multilayered personal, administrative, legal, and societal ramifications. Over the last century, various definitions of disability have appeared for diverse purposes, with little consensus across definitions. A “medical model” treats disability “as a problem of the person, directly caused by disease, trauma, or other health condition, which requires medical care. Management of the disability is aimed at cure or the individual’s adjustment and behavior change.”^1,2 In the past 50 years, a “social model” has viewed disability “mainly as a socially created problem, and basically as a matter of the full integration of individuals into society. Disability is not an attribute of an individual, but rather a complex collection of conditions, many of which are created by the social environment.”² Judy, for example, sees communication problems she confronts in her workplace not as her personal deficit, but as failures of the majority hearing world to accommodate communication with a linguistic minority.

In 2001, the World Health Organization approved the International Classification of Functioning, Disability and Health (ICF), which attempts to integrate medical and social models of disability.^2,3 The ICF identifies three interrelated concepts: “Impairments are problems in body function or structure such as a significant deviation or loss. Activity is the execution of a task or action by an individual. [and] Participation is involvement in a life situation.” The ICF defines disability as an “umbrella term for impairments, activity limitations or participation restrictions,” conceiving “a person’s functioning and disability … as a dynamic interaction between health conditions (diseases, disorders, injuries, traumas, etc.) and contextual factors,” including environmental and personal attributes.² As discussed in the following, the Americans with Disabilities Act (ADA, P.L. 101-336) adopted an even more expansive definition of disability.

Today’s broad definition of disability carries important lessons for clinicians, primarily because of potential effects on patient–clinician communication and incorporating the disability appropriately into treatment plans. Clinicians should approach clinical encounters with persons with disabilities just as they do with other patients, starting with the chief complaint and then, as necessary, learning more about any impairments when asking history questions. It is useful for the clinician to learn the patient’s view of the impairment. In some instances, impairments may be irrelevant to the reason patients seek care. For example, Judy’s identification as a linguistic minority rather than as someone with a disability should be known and respected, regardless of how social programs or legal mandates would categorize her.

In addition, the social definition highlights the relationships between individuals and their daily environments. Interventions that affect the interplay between them (e.g., various assistive technologies) or even the environment itself (e.g., ramps at home entrances) may prove extremely efficacious in restoring persons to safe and independent functioning; thus, the health care provider’s role in “treating” disability includes adjustments not only to the impairment, but in recommended adjustments to the environment and the interplay between them.

Varying definitions impede efforts to determine the population prevalence of disability. Patterns of disability (e.g., by age, sex) vary depending on perspective. Nearly 20% of community-dwelling, civilian, US residents aged 5 years and older report at least some disabling condition, with rates rising sharply (to 50%) among persons aged 65 and older.² As noted earlier, disability frequently tracks with personal attributes that characterize vulnerable populations, including minority race, low educational attainment, high level of unemployment, and poverty.

Conditions relating to aging are the most common causes of sensory and physical disabilities. Cataracts and glaucoma, along with presbyopia, are the main causes of vision loss⁴; presbycusis is the most common reason for hearing loss⁵; and arthritis is the single most disabling condition among adult Americans.⁵ Overall, because of very high rates of hearing problems among white men, white persons are more likely than African-American, Hispanic, and other race individuals to report any sensory or mobility disability. However, African Americans report higher rates of mobility disabilities than do whites; relative rates for Hispanics vary depending on the nature of the physical impairment.

SOCIAL SECURITY PROGRAMS

In the late 1950s, Social Security began two programs authorizing cash benefits for persons, such as Jimmy, who cannot work because of disability: SSDI (under Title II of the Social Security Act) and Supplemental Security Income (SSI, under Title XVI). SSDI gives benefits to persons who are “insured” by virtue of having worked and contributed to the Social Security trust fund through withholdings on their earnings (SSDI also covers certain disabled dependents of insured persons). The 1972 Social Security Act amendments granted eligibility for Medicare to individuals who have received SSDI cash benefits for 2 years. Title XVI provides SSI payments to persons, including children, who are disabled, blind, or elderly and have passed a means test documenting limited income and resources. Persons qualifying for SSI immediately receive Medicaid coverage. Poor persons receiving SSDI also can obtain SSI benefits after passing the means test; some states supplement the federal income benefit with additional cash payments.

SSDI and SSI use identical definitions to determine whether working-age adults are “disabled”: Under a yes/no standard, persons either can or cannot engage in “substantial gainful activity” because of medically proven sensory, physical, or mental impairments.⁶ As codified by 1968 regulations, the disability evaluation starts with the “Listings of Impairments” (the so-called List), which itemizes impairments, grouped by body system, that should be sufficiently severe to preclude substantial gainful employment among adults.⁷ The List stipulates specific tests (e.g., radiographs) and physical examination findings (e.g., joint range of motion) required to validate each condition. Musculoskeletal conditions are the leading cause of disability eligibility.⁷

PHYSICIAN ROLE IN ELIGIBILITY ASSESSMENT

Typically, officials determining eligibility seek information from applicants’ own physicians, presuming that they have the greatest clinical knowledge of their patients’ conditions. Thus, when Jimmy sought benefits from Social Security, he was referred to his physician for an evaluation and completion of the appropriate paperwork. This sometimes causes tensions between patients and physicians, especially when physicians think that patients can still work and the patient disagrees. After all, physicians must document all forms honestly, based on their professional judgments. In such instances, physicians should thoroughly explore the reasons why persons wish to stop working. For example, in Jimmy’s case, his physician might believe that he is not significantly impaired and could work at another job requiring less physical labor.

How disagreements between patients and physicians are handled often depends on the nature of the interpersonal and professional relationships. When there is disagreement, one strategy is to show the patient the final evaluation, asking if he or she would like the physician to submit it. Often, if the patient is unhappy, he or she may simply seek the advice of another physician. Finally, it is important to note that in the final analysis, it is not the clinician who grants disability, but it is the agency or courts (see “Core Competency”).

AMERICANS WITH DISABILITIES ACT

According to its opening statement, the aim of the Americans with Disabilities Act is “to provide a clear and comprehensive national mandate for the elimination of discrimination against individuals with disabilities.” Title I charges the Equal Employment Opportunity Commission, established initially with the Civil Rights Act of 1964, with ensuring that employers do not discriminate because of disability against otherwise qualified individuals “in regard to job application procedures, the hiring, advancement, or discharge of employees, employee compensation, job training, and other terms, conditions, and privileges of employment” (Sec. 102(a)). Discrimination includes “not making reasonable accommodations to the known physical or mental limitations” (Sec. 102(b)(5)(A)). Title II prohibits discrimination or denial of services provided by public entities, while Title III prohibits discrimination involving public accommodations and services operated by private entities, including the “professional office of a health care provider, hospital, or other service establishment” (Sec. 301(7)(F)).

The ADA defines disability as: “(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” (Sec. 3(2)). In operationalizing this definition, the ADA differs fundamentally from other civil rights laws. For instance, to sue for racial or gender discrimination, plaintiffs do not need to prove that they belong to a particular race or gender group. However, to litigate under the ADA, individuals must prove, sometimes to a skeptical judiciary, that they are disabled before they can broach questions about discrimination.

Through various cases (Sutton et al. v. United Air Lines, Inc. and Murphy v. United Parcel Service, Inc., 1999; Toyota Motor Manufacturing Inc. v. Williams, 2002), the US Supreme Court further constrained the ADA’s reach, largely by delimiting the “major life activities” clause. Rejecting Supreme Court holdings in such cases, the Congress passed the Americans with Disabilities Amendments Act (ADAAA), which was signed into law in 2008. The ADAAA aims to broaden coverage by including lists of conditions that qualify as disabilities and eliminating other strictures that limited disability claims. Under ADAAA provisions, with his physician’s assertions about his debilitating lower extremity arthritis and difficulty working, Jimmy might pass muster as “disabled” even though he still functions around home, doing light chores and preparing meals.

Walking not only physically moves persons at will from point A to point B, but it also carries tremendous cultural significance. The US ethos assumes citizens are free to move at will, act independently, be self-reliant, and take control, not be a burden to others. Bipedal, upright movement permeates aphorisms, connoting independence, autonomy, perseverance, strength, achievement: “standing on your own two feet,” “walking tall,” “standing up for yourself,” “taking things in stride,” and “climbing the ladder of success.” If their walking progressively fails, people can become embarrassed, ashamed, terrified of losing control, and afraid of being called lazy. Especially when older, people can feel that worsening walking is inevitable, something to be borne without complaint and hidden from view, something physicians can do little to help.⁸ Some, such as Tom, believe they can beat the problem by sheer willpower. In addition, Tom fears, not without reason, that he will lose his job if his boss notices his increasing debility.

THE ACT OF WALKING

Walking involves multiple interactive components, including gait, balance, strength, and endurance. Gait is the physical action of walking—a repeating cycle of movements encompassing one step with each foot. The gait cycle involves the stance phase (about 60% of the gait cycle) and the swing phase (the other 40%). The stance phase splits further into the double-leg stance (both feet contacting the ground) and the single-leg stance. One way to increase stability is to increase the time spent in double-leg stance. As people age, stride length shortens, thus resulting in larger proportions of walking time spent with two-leg support.

During the gait cycle, a person’s center of mass (COM, located midway between the hips) moves rhythmically up and down and side to side, while transferring weight from one leg to the other. People naturally adjust their limb and trunk muscles, counterbalancing arm swings and walking speeds to minimize COM movements and maintain their balance (the ability to control upright posture). Abnormalities that distort smooth, wavelike COM movement, such as the hemiplegic gait of strokes or efforts to avoid weight bearing on painful hips or knees, increase the energy required to walk. Walking slowly actually demands more energy for muscles and other structures to provide additional balance. If persons with impairments walk slowly, they therefore consume more energy than do others while walking the same distance.

TAKING A WALKING HISTORY AND EVALUATING MOBILITY

Asking about physical activity should be part of a complete primary care evaluation. Patients’ abilities to walk distances or perform other physical activities have long been used as explicit clinical indicators of cardiorespiratory endurance. Carefully questioning patients with, for example, heart failure or chronic obstructive pulmonary disease about how far they can walk before becoming short of breath provides important information about the severity of those diseases. Sometimes clinicians make patients walk around the office while monitoring their oxygenation via an oximeter. However, this does not constitute a formal gait analysis.

Major primary care textbooks say little about evaluating gait, and primary care clinicians often fail to recognize fully patients’ functional deficits. Some primary care clinicians observe patients as they walk into examining rooms or climb onto examining tables; however, these efforts are neither rigorous nor consistent. Only a few ask their patients to walk down the corridor and formally evaluate their gait. Evaluation tools do exist to assess walking, requiring nothing more sophisticated than a hallway, chair, and stopwatch. One that has been validated for elderly populations is the “Get Up and Go Test.”⁹ At a minimum, assessments provide a critical baseline evaluation (Box 42-1).