The Definition and Measurement of Disability

1. The Definition and Measurementof Disability The Work of the Washington Group on Disability Statistics Jennifer H. Madans National Center for Health Statistics, USA for the Washington Group on Disability Statistics

2. This presentation will cover: • Disability definition and the International Classification of Functioning, Disability and Health – ICF • Disability measurement and the Washington Group on Disability Statistics – WG

3. The Washington Group on Disability Statistics (WG) • In June of 2001, the UN International Seminar on the Measurement of Disability recommended the development of principles and standard forms for global indicators of disability to be used in censuses • There was a broad consensus on the need for population based measures of disability for country use and for international comparisons

4. Global disability prevalence rates* * Sources and methodologies are country specific

5. The WG was created to: • Foster international cooperation in the area of health and disability statistics • Untangle the web of confusing and conflicting disability estimates • Develop a small set of general disability measures suitable for use on Censuses • Develop extended set/s of items to measure disability on population surveys • Address methodological issues associated with disability measurement

6. Our understanding of disability has changed: from: a medical definition – based on a medical condition as an individual pathology to: a concept based on the consequences of diseases - on functional capacity and/or social participation

7. Moving from Concept to Definition to Measurement: The Conceptual Model ICF selected as the conceptual model: • Common point of reference • Common vocabulary • Does NOT provide an operational definition or a way to measure the concepts

8. Health Condition (disorder/disease) Participation (Restriction) Body Function & Structure (Impairment) Activities (Limitation) Personal Factors Environmental Factors The ICF Model Source: World Health Organization, 2001

9. Moving from Concept to Definition to Measurement: The Definitional Paradox • There is no single operational definition of disability • Different operational definitions lead to different estimates • The question you are trying to answer (the purpose) will determine which definition to use • Source of data can impact choice of purpose and definition

10. Purpose of Data Collection 3 major classes of purposes at aggregate level: • Service provision • Monitoring functioning in the population • Assess equalization of opportunities/ participation 2 criteria for selection of a purpose: • Relevance - particularly for policy makers and program officials • Feasibility - especially for international comparability

11. Purpose: Service provision • Seeks to identify those with specific needs, usually the most serious problems • Requires detailed information about the person and the environment • Influenced by the organization and structure of service organizations within a particular culture

12. Needs assessment/service provision • Benefit eligibility • Income support / social security • Subsidies • Device manufacture • Formal rehabilitation services • Education programs • Medical rehabilitation • Vocation rehabilitation • Personal assistant services • Advocacy services

13. Purpose: Monitoring functioning in the population • Seeks to identify all those with activity limitations or participation restrictions due to ‘health’ – e.g. ‘are you limited in the work you can do because of a health problem?’ • Difficult to craft questions • Response comparability is problematic since participation is culturally and environmentally determined

14. Example: Monitoring trends in functioning • Information is used to characterize population functioning • Focus on the interaction of people and environment Population reporting limitation in work

15. Purpose: Equalization of opportunities • Seeks to identify all those at greater risk than the general population of experiencing restrictions in social participation, for example in employment, education or civic life • Disability as a demographic • Civil rights definition

16. UN Convention on the Rights of Persons with Disabilities? UN Convention (2006): Persons with disabilities include those who have long-term physical, mental, intellectual or sensory impairments which in interaction with various barriers may hinder their full and effective participation in society on an equal basis with others.

17. Moving from Concept to Definition to Measurement: Measurement of equalization of opportunities • Locate the definition of disability at the most basic level of activity in core domains • Defined as the ability or inability to carry out basic actions at the level of the whole person (i.e. walking, climbing stairs, lifting packages, seeing a friend across the room)

18. Moving from Concept to Definition to Measurement: Measurement of equalization of opportunities • Measure functioning that defines disability status without accommodations to the extent possible (e.g., use of assistive devices, personal assistance) • Participation outcomes are measured with accommodations (e.g., are you employed) • Connection between ‘disability’ and participation is made during data analysis

19. Health Condition (disorder/disease) Participation (Restriction) Body Function & Structure (Impairment) Personal Factors Environmental Factors Locating Risk in the ICF Model ? ACTIVITY Source: World Health Organization, 2001

20. Example: Equalization of opportunities • Compares actual participation by level of risk for limitations in activity or participation • Disability used as a demographic % Employed

21. Criteria for inclusion of domains • Cross cultural comparability • Suitability for self-report • Parsimonious • Validity across various methodological modes

22. Mobility Walking Climbing stairs Bending or stooping Reaching or lifting Using hands Sensory Seeing Hearing Communicating Understanding Speaking Cognitive functions Learning Remembering Making decisions Concentrating Emotional functioning Interpersonal interactions Psychological well-being Possible question options

23. WG short set of questions for censuses: Because of a Health problem: • Do you have difficulty seeing even if wearing glasses? • Do you have difficulty hearing even if using a hearing aid? • Do you have difficulty walking or climbing stairs? • Do you have difficulty remembering or concentrating? • Do you have difficulty with (self-care such as) washing all over or dressing? • Using your usual (customary) language, do you have difficulty communicating (for example understanding or being understood by others)? Response categories: No - no difficulty; Yes - some difficulty; Yes - a lot of difficulty; Cannot do at all

24. What do we end up with? • Identify persons with similar types and degree of limitations in basic actions regardless of nationality or culture • Represent the majority (but not all) persons with limitations in basic actions in any one nation—no psychological or upper body functioning • Represent commonly occurring limitations in domains that can be captured in the Census context

25. Intended use of data • Compare levels of participation in employment, education, or family/social life for those with disability versus those without disability to see if persons with disability have achieved social inclusion • Monitor effectiveness of programs / policies to promote full participation can be monitored – UN Convention • Monitor prevalence trends for persons with limitations in specific basic activity domains

26. Limitations • One set of measures will not satisfy the multiple needs for disability data • Excluded populations: • very young children • institutionalized population • homeless • floating populations • It is not our purpose to: • identify every person with a disability within every community • replicate a population evaluated across a wider range of domains that would be possible with other forms of data collection – extended set

27. Work on Extended Measures • The WG is developing an extended set of questions that: • goes into greater depth on the same 6 domains covered by the short set of questions, and • includes additional domains of functioning such as learning, affect, pain and fatigue, • includes questions about age at onset and impact of the difficulty, • is currently being cognitively tested in preparation for subsequent field testing.