Understanding the linkages between perceived causative impairment and activity limitations among older people living in the community: a population-based assessment.

Costs associated with management of disability in the elderly population represent a substantial burden to the healthcare system, family and the individuals themselves, and are expected to increase over the coming decades.1, 2 The population of elderly persons with functional disability due to physical and cognitive impairment in the United States is expected to triple by 2049.3, 4 Consequently, assessment of the causes of disability is crucial to physical medicine and rehabilitation (PM&R) in preparation for developing guidelines and treatment planning, and in the evaluation of the relative benefits of various preventative and interventional strategies.3 The World Health Organization, through its recent development of the International Classification of Functioning, Disability and Health (ICF), defined disability as a multidimensional construct that distinguishes among impairment, activity limitation and participation restrictions.5 Impairments are problems with body function or structure. Activity limitations refer to difficulties encountered by the person when trying to perform a task. Participation restrictions relate to problems an individual encounters when trying to engage in life situations. Activity limitations have profound adverse consequences for the quality of life in elderly populations, and are strongly associated with increased mortality and further decline in functional status.6 More severe activity limitation is associated with increased healthcare utilization, including hospitalization, use of rehabilitation services, use of formal and informal home care, and admission to nursing homes.7–10 Activity limitations are typically divided into those involving basic activities of daily living (ADL)11 and those involving more complex instrumental activities of daily living (IADL).12 ADL and IADL limitations distinguish between more and less severe activity limitations, respectively, 13 and are classified in the “self care” and “domestic life” chapters of the ICF. 5 In addition to the types of activities limited (i.e. ADL versus IADL) the ways in which those activities are limited will influence how and the degree to which people living in the community are able to participate in life situations.14 The need for physical help versus supervision determines the amount and type of support the person requires, which, in turn, also potentially impacts the extent to which care givers are able to participate in their own lives.15, 16 A deeper understanding of the impairments people themselves or their close household contacts perceive as most limiting of activity could facilitate clinical care, policy and research. Such basic knowledge could support guidelines as well as intervention development for disability management, and provide a broad framework for studying the functional prognosis of populations of people with particular types of impairments. This work was stimulated by recognizing that the detailed classification of impairments by specific pathologic causes, illnesses or injuries would be too complex. Such an approach would lead to too many groups that were too small for statistical comparisons making the classification inoperable to research and clinical guideline development. A more sensible approach to classification would reduce numerous pathology-related conditions into functionally-associated classes of impairments that share similar features regarding the origin of the impairment and its possible association with specific types and qualities of activity limitation. Along these lines, a number of core datasets are being developed or have been developed, primarily in Europe, based on ICF concepts relevant for specific diagnoses and settings.17–18 This paper builds on the ICF core dataset concept by presenting a generic “perceived causative impairment classification system” intended to be relevant across the full population of community-dwelling elderly people with disabilities in the US. The system is intended to characterize activity limitations and impairments caused by particular types of conditions. Based, in part, on the body system structural impairment chapters defined by the ICF (Table 1), the causative impairment classification system organizes health conditions perceived as limiting activities into impairment categories using one or more of the following criteria. First, conditions can be caused by similar types of body system damage, such as impairments caused by injuries in the brain secondary to trauma, stroke or tumors. Second, conditions affecting multiple body systems may be grouped if they share common pathways to impairment, such as heart and lung injuries reducing energy. Third, they may be grouped if they lead to similar activity limitations, such as vision and hearing deficits that primarily influence people’s abilities to gather information from the environment and tend to lead to more complex IADL limitations. IADLs depend more heavily than do ADLs on interacting with, moving through and gathering information from the physical and social environments. Table 1 The Perceived Causative Impairment Classification Based on ICF Chapters The primary hypothesis was that particular causative impairments would be associated with IADL only versus ADL limitations, and with different qualities of dependency, i.e., physical help versus need for supervision. We anticipated that those whose activity limitations were attributed primarily to brain function or behavior rather than to other types of conditions would be more likely to have one or more ADL limitations as opposed to IADL limitations only. Also, they would be more likely to need a second person for help when performing ADL. In contrast, people with conditions impairing the cardiopulmonary or hematological systems, which primarily affect energy rather than the ability to move, would be more likely to have IADL limitations only.