Learning more about the long-term effects of aging with disability is an emerging priority for researchers, service providers, and policy analysts in the fields of both gerontology and rehabilitation. Thanks to dramatic post World War II advances in life expectancy and survivorship, most people with physical disability, like the population at large, can now expect to live to later- life and some to advanced old age. The changing demographics of long-term disability affect two primary groups of people-- those aging with developmental or early-life onset of disability, including cerebral palsy, mental retardation, polio, and multiple dystrophy, and those aging with young adult onset of disability such as spinal cord injury, traumatic brain injury and rheumatoid arthritis.

Estimates indicate that there may be as many as five to 10 million people alive today in the United States who are aging with these two types of long- term physical disabilities. The problem that must be addressed is that, as they age, many of these "survivors" start to experience the onset of new symptoms and functional limitations which threaten to further erode their health and independence and increase their need for services. Regardless of etiology, individuals experiencing these "secondary disabilities" frequently report similar problems such as unaccustomed fatigue, new muscle weakness, muscle and/or joint pain, difficulties walking, increased reliance on assistive devices and personal attendant services, loss of employment, social isolation, and discouragement or depression.

To understand the impact of secondary disabilities on individuals, families, and society, it is critical that we know at what point in the lifespan they occur. For unlike their non- disabled peers, many people with life-long disabilities experience the signs and symptoms of "aging" at an earlier stage in their life, when the needs for income and the demands of work and family are the greatest. Therefore, in addition to undermining independence, the onset of secondary disabilities may violate strongly held beliefs regarding the "normal" structure of the life course.


Dearth of Research

Despite increasing prevalence, and the potential "costs"-- both human and monetary-- of secondary disabilities, little research exists describing the natural history of aging with physical disability. In fact, data on aging are typically missing from most empirical studies of life-long disability. One explanation for this gap in our knowledge is the lack of an integrated framework that combines the bio-psycho-social theories of aging and adult development from gerontology with the disability models and functional assessment tools of medical rehabilitation.

The life course perspective of sociology offers a promising framework for expanding our knowledge of age-related changes associated with long-term disabilities. Unlike most rehabilitation approaches, which emphasize impairment and functional limitations, the life course perspective focuses on describing the temporal structure of disability and examining the consequences of variations in the timing of disability events for the well-being of survivors as they age.


The Life-Course Perspective

Drawing on the work of Scheer and Luborsky, Figure 1 presents a schematic diagram of aging with a disability from a life course perspective. Within this framework, the long- term effects of disability are seen as a complex process involving the intersection of individual or chronological aging, social aging, and historical time, all of which are superimposed upon the unique features of the "disability timeline." This last component of the life course reflects variations in the temporal structure of disability- related events, such as age of onset of primary and secondary disability, by type of disability (e.g., cerebral palsy and polio versus spinal cord injury and stroke). The historical period corresponds to the socio- cultural context in which an individual acquires his or her disability, is socialized and ages. Because this dimension captures macro- level changes in societal attitudes, government policies and rehabilitation methods, it is critical in shaping the life chances of persons with disability.

A recently completed five-year Comparative Study of Aging and Disability, conducted at Rancho Los Amigos Medical Center in Downey, CA, demonstrates the utility of the life course perspective for enhancing our understanding of who is most at risk the later-life effects of early-life disability. Using data from 120 polio survivors with a mean age of 63, findings indicate that both the age of the person at acute onset and the historical period are significantly related to the severity of initial impairment as well as to the physical and psychosocial well- being of survivors at time- of measurement.

Participants who contracted polio earlier in the century and at younger ages were significantly less impaired initially, as measured by the number of limbs affected, than their counterparts who contracted polio later during the peak of the epidemics and at an older age. Timing and initial severity were also positively related to the likelihood of experiencing the new health problems and functional losses associated with post- polio syndrome (PPS) an average of 48 years later. As age and historical period of onset and the number of limbs affected increased so did the percentage of survivors meeting Halstead's criteria for PPS (Halstead, 1988). Interestingly, those with and without PPS did not differ significantly by chronological age or duration of disability. This suggests that neither "aging" per se or the mere passage of time are adequate explanations of who is most at risk for secondary disabilities.

Finally, the onset characteristics of polio were also linked to the mental health status of survivors at time- of- measurement. Again, it was those who were most severely impaired and experienced polio after 1940 and at older ages, who were most at risk for depressive symptoms and low scores on an acceptance of disability measure. Together, these findings illustrate the potential of the life course perspective to expand our understanding of how the meaning and consequences of disability are shaped by both the historical context and life course stage in which they occur.


References

J. Scheer and M. Luborsky, Post-polio sequel: The cultural context of polio biographies. Orthopedics, 1991; 14:1173-1181.

L.S. Halstead, Late complications of poliomyelitis. In J. Goodgold, ed., Rehabilitation Medicine. C.V. Mosby, St. Louis, MO, 1988.