The WHO International Classification of Functioning, Disability and Health (ICF)
The functioning of an individual in a specific domain reflects an interaction between the health condition and the contextual environmental and personal factors. There is a complex, dynamic and often unpredictable relationship among these entities and understanding this interaction is crucial to understand what disability is and how the concepts of functioning and disability can be defined and operationalized.
The WHO International Classification of Functioning, Disability and Health (ICF) is a framework for organising and documenting information on functioning and disability (WHO 2001). The ICF was approved for use by the World Health Assembly in 2001, after extensive testing across the world involving people with disabilities and people from a range of relevant disciplines. A companion classification for children and youth (ICF-CY) was published in 2007. The ICF integrates the major models of disability. It recognises the role of environmental factors in the creation of disability, as well as the relevance of associated health conditions and their effects. It conceptualises functioning as a ‘dynamic interaction between a person’s health condition, environmental factors and personal factors’.
ICF provides a standard language and conceptual basis for the definition and measurement of disability, and it provides classifications and codes. It integrates the major models of disability – the medical model and the social model – as a “bio-psycho-social synthesis”. It recognises the role of environmental factors in the creation of disability, as well as the role of health conditions. Functioning and disability are understood as umbrella terms denoting the positive and negative aspects of functioning from a biological, individual and social perspective. The ICF conceptualises a person’s level of functioning as a dynamic interaction between her or his health conditions, environmental factors, and personal factors. It is a biopsychosocial model of disability, based on an integration of the social and medical models of disability. The ICF therefore provides a multi-perspective, biopsychosocial approach which is reflected in the multidimensional model of health.
Health has been defined in the WHO Constitution as ‘a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity’ (Constitution of the World Health Organization, WHO 1948). The ICF provides a scientific, operational basis for describing, understanding and studying health and health-related states, outcomes and determinants. The ICF is recognised as a reference member of the WHO Family of International Classifications (WHOFIC), and complementary to the International Statistical Classification of Diseases and Related Health Problems (ICD). Health conditions are classified using the ICD (most current version is ICD-11), which provides codes for diseases, disorders, injuries or other health problems thus an aetiological framework. The health and health-related states associated with any health condition can be described using ICF. The ICF and ICD are two complementary WHO reference classifications; both members of the WHOFIC. ICF is not associated with specific health problems or diseases; it describes the associated functioning dimensions in multiple perspectives at body, person and social levels. From WHO’s perspective, ICF is most relevant to the health information component of health systems, complementing its two other data classifications, ICD and the International Classification of Health Interventions (ICHI), which together allow for the routine collection of data concerning all three indicators of health status – mortality, morbidity, and functioning.
Definition of disability and the biopsychosocial model
The ICF provides a framework for the description of human functioning, on a continuum. It is important to remember that it classifies functioning, not people. Because the development and testing of the ICF involved people from a broad range of backgrounds and disciplines, including people with disability, the ICF has a wide range of potential applications. People use the ICF across broad sectors including health, disability, rehabilitation, community care, insurance, social security, employment, education, economics, social policy, legislation and environmental design and modification.
The ICF conceptualises functioning and disability in the context of health, and therefore does not cover circumstances that are brought about solely by socioeconomic or cultural factors. Nevertheless, if poverty results in a health condition such as malnutrition, related functioning difficulties can be described using the ICF.
The ICF has been accepted as one of the United Nations social classifications and provides an appropriate instrument for the implementation of stated international human rights mandates as well as national legislation. Hence, the ICF provides a valuable framework for monitoring aspects of the UN Convention on the Rights of Persons with Disabilities (UN 2006), as well as for national and international policy formulation.
In 2006 the WHO Family of International Classifications (WHO-FIC) Network established the Functioning and Disability Reference Group (FDRG) to advise on functioning, disability and health classification and coding issues. The FDRG, with members from more that 30 WHO collaborating centres around the world, has developed a work program to enable it to provide well researched advice. Topics include coding guidelines, ICF updates, ICF-ICD joint use, ICF-ICHI, use of WHO DAS 2.0, education, ethical use of ICF, measurement and environmental factors. The FDRG works collaboratively with other committees and reference groups in the WHO-FIC Network to address these issues and to create a common language for health, disability and functioning.
Definitions and categories in the ICF are worded in neutral language, wherever possible, so that the classification can be used to record both the positive and negative aspects of functioning. In classifying functioning and disability, there is not an explicit or implicit distinction between different health conditions.
Disability is not differentiated by aetiology. ICF clarifies that we cannot, for instance, infer participation in everyday life from medical diagnosis alone. In this sense ICF is aetiology-neutral: if a person cannot walk or go to work it may be related to any one of a number of different health conditions. By shifting the focus from health condition to functioning, the ICF places all health conditions on an equal footing, allowing them to be compared, in terms of their related functioning, via a common framework. In developing collections of information on functioning and disability it is important to consider all components of the ICF.
A common definition of disability is crucial to understanding and improving outcomes for people with disabilities as well as for increasing the power of information through the ability to relate data from different sources, such as in service settings and at the population level. When consistent language and concepts are used, they facilitate comparisons, complementary information and knowledge building.
Functioning, disability and the components of the ICF have precise definitions that have been so far translated in more than 65 languages. Body functions are the physiological functions of body systems (including psychological functions). Body structures are the anatomical parts of the body such as organs, limbs and their components. Impairments are problems in body function and structure such as significant deviation or loss. Activity is the execution of a task or action by an individual. Participation is the involvement in a life situation. Activity limitations are the difficulties an individual may have in executing activities. Participation restrictions are problems an individual may experience in involvement in life situations. Environmental factors are the physical, social and attitudinal environment in which people live and conduct their lives. These are either barriers to or facilitators of the person’s functioning. (WHO ICF 2001).
Human Functioning: to reconceptualize health
Functioning is an umbrella term for body function, body structures, activities and participation. It denotes the positive or neutral aspects of the interaction between a person’s health condition(s) and that individual’s contextual factors (environmental and personal factors). Disability is an umbrella term for impairments, activity limitations and participation restrictions. It denotes the negative aspects of the interaction between a person’s health condition(s) and that individual’s contextual factors (environmental and personal factors).
Two constructs, ‘performance’ and ‘capacity’, can be used in operationalising the qualifier scale for the activities and participation domains. These constructs provide a way of indicating how the environment (in which measurement has taken place) impacts on a person’s activities and participation, and how environmental change may improve a person’s functioning. ‘Capacity’ relates to what an individual can do in a ‘standardised’ environment. ‘Performance’ relates to what the person actually does in his or her ‘current’ (usual) environment. The gap between capacity and performance reflects the difference between the impacts of current and uniform environments, and thus provides a useful guide as to what can be done to the environment of the individual to improve performance (WHO ICF 2001).
From a public health perspective, functioning augments the biomedical view of health measured in terms of the indicators of mortality and morbidity. Functioning constitutes WHO’s third health indicator of health. Avoiding premature mortality and controlling morbidity are obviously important to us, as individuals and as society at large, but only to the extent to which they are conducive to enhanced functioning and so better health. Population aging, adding more years to our lives, underscores the equal importance of adding more life to our years. The increased prevalence of non-communicable diseases and chronic health conditions – the so-called compression of morbidity which lead to a decline in functioning – is concerning, and from the perspective of society they warrant increased investment in prevention and cure. But the impact of these trends also points to the need to prepare our healthcare systems to focus on optimizing functioning.
Moreover, operationalizing health as human functioning completes the picture of health envisaged by SDG3 by explaining why health is a driver of individual well-being and, in turn, why population health contributes to societal welfare.
Human functioning as the third indicator of health (complementing mortality and morbidity) provides a basis for reconceptualizing multidisciplinary health sciences; a new interdisciplinary science field – human functioning sciences – itself holds promise to integrate diverse research inputs and methods to provide a fuller understanding of human health. Implementing functioning as defined and conceptualized in the International Classification of Functioning, Disability and Health could profoundly benefit practices, research, education, and policy across health systems and health strategies and help integrate health and social systems. It also offers a foundation for reconceptualizing multidisciplinary health sciences and for augmenting epidemiology with information derived from peoples’ lived experiences of health.
Conclusions
As this Plenary of the PASS shows, it is necessary today for “Changing the Social Determinants of Disabilities and Building a New Culture of Inclusion” to identify what are the specific determinants that in the cultural, family, educational, political, economic, and employment spheres represent the barriers that increase the disability of a society and prevent persons with disabilities from fully participating in social life by making their original contribution. This is what matters to people, and the COVID-19 pandemic showed to everybody that health is a key component for each individual and the environment plays a crucial role in determining functioning.
During their life all people experience decline in body functioning as well as any health condition that can cause pain, anxiety, fatigue and other sensory, mobility, and cognitive impairments. What people can do in their daily life is what matters to people DESPITE the presence of a health condition, this is the lived experience of health and functioning. This essential component of lived health complementing the traditional biomedical understanding of health, creates a more meaningful operationalization of what health means to us.
Human functioning is the bridge that links health to individual well-being and societal welfare. Functioning incorporates biological health (the physiological and psychological functions and anatomical structures of the body that constitute the intrinsic health capacity of a person to perform human activities) and lived health (the individual’s actual performance of activities in interaction with their actual physical, built, and social environments) (Bickenbach J et al.2023).
Disability is thus a manifestation of possible variations in human functioning resulting from the interaction with environments that are barriers, rather than a mental or physical impairment to be discarded.
As Pope Francis affirms, “we need the courage to give voice to all those that suffer discrimination because of their disability as unfortunately in some Countries, still today, it is difficult to recognize equal dignity to all”. Therefore, disability poses a decisive challenge: a new global culture of inclusion must be developed by eliminating the barriers that hinder the full citizenship of persons with disabilities and their “unique contribution to the common good through their remarkable life stories” (Fratelli tutti, 98).
References
World Health Organization. ICF International Classification of Functioning, Disability and Health. Geneva: World Health Organization (2001).
Üstün TB. Chatterji S. Bickenbach J. Kostanjsek N. Schneider M. The International Classification of Functioning, Disability and Health: a new tool for understanding disability and health. Disabil Rehabil. 2003; 25(11-12):565-571.
Leonardi, Matilde and Andrea Martinuzzi. “ICF and ICF-CY for an innovative holistic approach to persons with chronic conditions”. Disability and Rehabilitation 31 (2009): S83-S87.
Leonardi M, Lee H, Kostanjsek N, Fornari A, Raggi A, Martinuzzi A, Yáñez M, Almborg AH, Fresk M, Besstrashnova Y, Shoshmin A, Castro SS, Cordeiro ES, Cuenot M, Haas C, Maart S, Maribo T, Miller J, Mukaino M, Snyman S, Trinks U, Anttila H, Paltamaa J, Saleeby P, Frattura L, Madden R, Sykes C, Gool CHV, Hrkal J, Zvolský M, Sládková P, Vikdal M, Harðardóttir GA, Foubert J, Jakob R, Coenen M, Kraus de Camargo O. 20 Years of ICF-International Classification of Functioning, Disability and Health: Uses and Applications around the World. Int J Environ Res Public Health. 2022 Sep 8;19(18):11321. doi: 10.3390/ijerph191811321. PMID: 36141593; PMCID: PMC9517056.
Stucki G, Bickenbach J. Functioning: the third health indicator in the health system and the key indicator for rehabilitation. Eur J Phys Rehabil Med (2017) 53:134–8. doi: 10.23736/s1973-9087.17.04565-8.
Bickenbach J, Rubinelli S, Baffone C and Stucki G. The human functioning revolution: implications for health systems and sciences. Front Sci (2023) 1:1118512. doi: 10.3389/fsci.2023.1118512.
United Nations, Department of Economic and Social Affairs, Population Division. World population ageing 2015 – highlights (St/Esa/Ser.A/368) (2015). New York: United Nations. Available at: https://www.un.org/en/development/desa/ population/publications/pdf/ageing/WPA2015_Highlights.pdf (Accessed November 26, 2023).
World Health Organization. World report on ageing and health. Geneva: World Health Organization (2015). Available at: https://www.who.int/publications/i/item/9789241565042 (Accessed April 3 2024).
United Nations 2006. Convention on the Rights of Persons with Disabilities. http://www.un.org/disabilities/default.asp?navid=12&pid=150
United Nations. Transforming our world: the 2030 agenda for sustainable development. Available at: https://sdgs.un.org/2030agenda (Accessed April 3, 2024).
World Health Organization. International Classification of Health Interventions. Geneva: World Health Organization (2018).Available at: https://www.who.int/standards/classifications/international-classification-of-health-interventions ( Accessed April 3, 2024).
WHO Family of International Classifications Network (including a list of Collaborating Centres): http://www.who.int/classifications/network/en/
Pope Francis, Encyclical letter Fratelli tutti (2020) https://www.vatican.va/content/francesco/en/encyclicals/documents/papa-francesco_20201003_enciclica-fratelli-tutti.html (Accessed 4 April 2024).