Definition And Prevalence
Disabilities have become a major health-related issue for an increasing number of people in the United States. Based on data from the 1988 National Health Interview Survey, it is estimated that 35 million Americans have a disability (Pope and Tarlov 1991). Furthermore, the overall prevalence of disabilities has been increasing in the United States, primarily because of biomedical advances that are able to keep people alive longer. This is the case for all ages across the lifespan, from very premature infants to the elderly. However, maintaining life does not always mean cure. Many more individuals live with the residue of what cannot be cured; they live with chronic conditions, and many chronic conditions create disability or gradually lead to disability over time. By definition, disability is the inability to engage in any substantial gainful activity by reason of some medically determined physical or mental impairment that can be expected to last or has lasted for a continuous period of not less than twelve months. Disability is the gap between a person's capabilities and what the environment expects a person to be able to perform in personal, familial, and social roles (Pope and Tarlov 1991). When estimates of the prevalence of disabilities are made, primary social roles are defined as follows: "playing" for children under five years; "going to school" for children ages five to seventeen; "working or keeping house" for adults ages eighteen to sixty-nine; and "living independently" for adults over seventy.
The main causes of activity limitation leading to disability are mobility impairments (38%); chronic diseases (32%); sensory impairments (8%); and intellectual impairments, including mental retardation (7%) (LaPlante 1988). Both the prevalence and the severity of disabilities increase with age. The percent of each age group with a disability is 2 percent of children under five years, 8 percent of children ages five to seventeen years, 10 percent of adults eighteen to forty-four years, 23 percent of adults forty-five to sixty-four years, 36 percent of adults sixty-five to sixty-nine years, and 38 percent of adults over seventy (National Center for Health Statistics 1989). For children under eighteen years, intellectual limitations and chronic diseases are the major causes. Above eighteen years, mobility impairments are the primary cause. For those between eighteen and forty-four years of age, accidents and injuries are a major contributing factor to mobility impairment; among older ages, mobility impairment is more the result of chronic disease, such as arthritis.
Not all chronic conditions are associated with disability. Some chronic conditions cause no limitations. For those that do, the degree of limitation varies from minor to being unable to perform a major activity, such as working. For those conditions associated with disability, families increasingly have taken over a major role in providing assistance and care for their members who are disabled (Chilman, Nunnally, and Cox 1988). Very few families can expect to go through their life course without caring for at least one member with a disability. In many instances, however, the onset and severity of disability can be prevented or postponed, especially those related to chronic diseases. This is influenced by the person's lifestyle, access to regular medical care, and willingness to take an active role in managing his or her health condition. The family, of course, is a critical social context influencing how an individual responds to a chronic condition, as well as how an individual responds to physical, intellectual, and sensory impairment. In this way the family can have a major impact on the course of chronic conditions, if and when disability emerges, and how severe the disability is.