Older persons consistently indicate that maintaining independence is their top priority. The capacity to complete a series of day-to-day actions and tasks with as little difficulty as possible, irrespective of having chronic illnesses, determines good health and quality of life and is an important element of successful aging. However, for almost everyone, aging brings functional challenges that can compromise independence. Chronic and acute conditions, which are increasingly common as people age, are the trigger points for the disablement process. These conditions cause the development of impairments in specific body systems, which then result in functional limitations, eventually culminating in disability (Figure 5–1). Disability is defined as difficulty or need for help doing activities in any domain of life (from personal care to hobbies) due to a health or physical problem. For example, diabetes (chronic condition) leads to peripheral neuropathy (impairment), which then leads to poor balance and mobility (functional limitation), which finally leads to an inability to bathe in the tub/shower (disability).
For chronic diseases such as diabetes and hypertension, the linkage to disability is indirect and often distant, spanning years to decades. For other chronic diseases, such as knee osteoarthritis and dementia, the linkage is more direct and less distant, spanning months to years. For acute diseases and injuries, such as infections and fall-related injuries, the linkage is often direct and happens suddenly.
This process leading to disability is always influenced by an individual’s intrinsic factors (socioeconomic status, lifestyle, behavioral and psychological aspects) and environmental factors (access to medical care, medications and other therapeutic regimens, devices and structural modifications for accessibility). Although some risk factors are nonmodifiable, such as advanced age and female gender, most of them are potentially modifiable such as current smoking, excessive alcohol consumption, sedentary lifestyle, limited access to health care and social services, polypharmacy and the use of potentially inappropriate medications (eg, anticholinergic drugs and benzodiazepines), and challenges in home structure (eg, broken flooring and stairs without handrails).
Disability should not be considered a personal characteristic but instead a gap between personal capability and environmental demand. It is important to distinguish between intrinsic disability and actual disability. With intrinsic disability, one might be disabled without environmental modifications or adaptive equipment, but providing these modifications and assistance restores independence. With actual disability, one is disabled even with these modifications and assistance. This distinction notes the importance of detecting modifiable factors, especially those external to the individual, that influence the capacity of a person to keep their function. For example, persons with diabetes and peripheral neuropathy who have difficulty bathing could maintain their independence for a longer time if provided adequate access to health care assistance and if they receive physical rehabilitation and simple home modifications (eg, grab bars in the bathroom).