Human Functioning: Developments and Grand Challenges

Abstract

Like many ground-breaking innovations, the conceptual thinking that went into The World Health Organization's International Classification of Functioning, Disability and Health (ICF) in the early 1990s had been anticipated in the literature for decades, although formally endorsed by the WHO in 2001, the result was a true paradigm shift (1). With the ICF, WHO made it clear that, although health states are purely biological phenomena, what matters to people about their health is not merely these biological processes but also the concrete impact on their daily lives: what they can do and be, the actions they perform and the life goals and aspirations they can achieve. The ICF made it clear that challenges to our health—disease, injuries, and the natural process of aging itself—bring about decrements in body functions and alterations of body structure, and these changes, in interaction with the environment, can negatively affect—sometimes trivially, sometimes profoundly—what we can do and achieve in our lives. To capture this multifaceted and continuous phenomena, the ICF proposes the term functioning—the sum total of functions and structures of the body and mind, the actions people perform, and the complex and socially-embed life activities they participate in. Functioning, as a term of science, requires both a conceptual description or model and, for scientific description, operationalization and measurement, a classification of the lived experience of health. The ICF provided both. The notion of functioning has in the last 20 years made it possible to clarify the concept and practice of healthcare, and most particular the concept and practice of rehabilitation. The ICF notion of functioning provides a clearer understanding of the health and social impact of future trends in population aging and increased prevalence of non-communicable diseases, trends that will reveal the increasing need for, and social value of rehabilitation as a health strategy. Since 2001, the ICF has been widely and diversely applied as a standard classification, an international reference language for the collection of information about the lived experience of health. The ICF complements and supplements the WHO's International Classification of Diseases (ICD) (2) as well as, more recently, the International Classification of Health Intervention (ICHI) (3). WHO's primary purpose in promulgating each of these standards is to ensure comparability of international health information—information that is of practical use to practitioners and researchers to explain and influence functioning both clinically and at the population level, and to policy-makers striving to improve the performance of national health systems to respond to the functioning needs of individuals and populations. The future of e-health and all digital applications of health information depends on data standardization, as does a more comprehensive epidemiology that goes beyond the standard health indicators of mortality and morbidity. The conceptual foundations of the ICF notion of human functioning has also spurred research and applications that have had a fundamental and diverse impact on health sciences and health and social policy. Functioning is conceptualizes in the ICF in terms of a person-environment interaction, which in turn has led to the important conceptual distinction between a person's intrinsic health capacity and the person's actual, real world performance in which her or his physical, human-built, attitudinal, and socio-political environment may hinder or enhance performance. This model has been particularly useful in clarifying the notion of disability as a problem, decline, or non-optimal functioning in one or more domains. This understanding of disability has lead to a rethinking of the most prominent policy applications of the notion of disability, and in particularly that of disability assessment and determination processes for health and social benefits, including the need for vocational rehabilitation. Rather than understanding disability purely from the perspective of biomedical phenomena, the ICF has underwritten the more robust and valid notion of disability as the outcome of an interaction between intrinsic health capacity, personal factors, and the environment. The last two decades of research and application of the ICF and its key notion of functioning point to an active future of grand challenges for rehabilitation. As one of the five health strategies recognized by the WHO, rehabilitation has historically been undervalued and misunderstood, in part because, unlike curative medicine and health promotion and disease prevention, rehabilitation seemed to have a somewhat vague aim and purely reactive posture. Recent work on the conceptualization of rehabilitation (4–7), however, has argued that the notion of functioning may be the key to a new understanding in which the aim of rehabilitation is to optimize functioning in the face of demographic and epidemiological trends that point to a future of increased population disability. It remains a challenge how this insight can be used to further clarify the role and purpose of rehabilitation as a fundamental health strategy. Equally challenging is to ensure that rehabilitation is not merely a high-income country health strategy but its aim and scope can be effectively implemented in low- and middle-income countries as well. In practical terms, clinicians require tools and an operational language in which to assess their patients and evaluate the quality and effectiveness of rehabilitation interventions. Given the importance of this area of clinical practice, there is a growing literature on the use of ICF and functioning in the development of clinical assessment, evaluation and quality management tools and methodologies (8–11). The challenge in the future is to both to continue this development, and as far as possible, to ensure...