The Definition and Measurement of Disability: The Work of the Washington Group

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The Definition and Measurement of Disability The
Work of the Washington Group

• Jennifer Madans
• Associate Director for Science
• US National Center for Health Statistics and The
  UN Washington Group
• November 9, 2006

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The Washington Group on Disability Statistics

• In 2001, the UN International Seminar on the
  Measurement of Disability recommended the
  development of principles and standards for
  global indicators of disability to be used in
  censuses
• The Washington Group was formed under the aegis
  of the UN Statistical Commission to
• Foster international cooperation in the area of
  health and disability statistics
• Develop disability measures suitable for censuses
  and surveys
• Untangle the web of confusing and conflicting
  disability estimates

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Current Problem

• Currently national censuses in developing
  countries use one of three types of questions
  that provide widely differing estimates of
  national prevalence of disability
• The three types of questions include
• A. Generic question about the presence of a
  condition
• B. Generic questions about the presence in the
  household of a person with a disability followed
  by a list of impairments
• C. Checklist of impairments

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Reported Disability Prevalence Varies Widely
Bangladesh 0.8 Niger
1.3 Philippines 1.3 Colombia
1.8 Egypt 4.4 Germany 8.4 United
States 15.0 Australia 18.0 Source UN
Statistics Division
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Washington Group Objectives

• Develop a small set/s of disability questions
  that could be used on Censuses/surveys
• Recommend extended set/s of items to measure
  disability as components of population surveys /
  supplements
• Address methodological issues associated with
  disability measurement

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Preliminary work to meet objectives

• Clarify the purpose of data collection in order
  to identify appropriate measures
• Understand choices being made when time, expenses
  and respondent burden limit number of questions

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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

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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
• Need to understand the choices that are being
  made when a purpose and a definition are chosen
• Need to understand the choices that are being
  made when time, expenses and respondent burden
  limit number of questions

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Purpose of Data Collection

• 3 major classes of purposes at aggregate level
• Service Provision
• Monitoring functioning in the population
• Assess equalization of opportunities
• 2 criteria for selection of a purpose
• Relevanceparticularly for policy makers and
  program officials
• Feasibility

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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

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Purpose Monitoring functioning in the population

• Seeks to identify all those with activity or
  participation limitation
• Response comparability problematic since
  participation is culturally and environmentally
  determined

Population reporting work limitation
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Purpose Equalization of opportunities

• Seeks to identify all those at greater risk than
  the general population for limitations in
  activity or participation
• Disability as a demographic

Employed
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Applying criteria to select purpose

• Service provision
• Level of detail necessary not feasible in a
  census format
• Nature of service provision varies across
  cultures
• Monitoring functioning
• Response comparability problematic since
  participation is culturally and environmentally
  determined
• Assessing equalization of opportunities
• If we conceive of disability toward the most
  basic elements of activity, without tying it to
  participation, we limit the number / types of
  questions thus enhancing feasibility

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Moving from Concept to Definition to Measurement
Measurement of equalization of opportunities

• Locate the definition of disability at the most
  basic level of activity/participation in core
  domains
• This level is associated with the ability or
  inability to carry out basic bodily operations at
  the level of the whole person (i.e. walking,
  climbing stairs, lifting packages, seeing a
  friend across the room)
• Connection between disability and participation
  can be made during data analysis

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Locating Risk in the ICF Model
Health Condition
ACTIVITY
?
Body Functions Structure
Participation
Source ICF, WHO, 2001
Environmental Factors
Personal Factors
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Criteria for inclusion of domains

• Cross cultural comparability
• Suitability for self-report
• Parsimony
• Validity across various methodological modes

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WG Questions for Censuses

• Core Questions
• 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?
• Additional Questions
• Do you have difficulty with self-care, such as
  washing all over or dressing?
• Because of a physical, mental, or emotional
  health condition, do you have difficulty
  communicating (for example understanding others
  or others understanding you)?
• Response categories
• No - no difficulty Yes some difficulty Yes
  a lot of difficulty
• Cannot do at all

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Objectives

• Identify persons with similar types and degree of
  limitations in basic activities regardless of
  nationality or culture
• Represent the majority (but not all) persons with
  limitations in basic activities in any one nation
• Represent the most commonly occurring limitations
  in basic activities within any country
• Capture persons with similar problems across
  countries

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Intended use of data

• Development of a demographic means of
  understanding disability Can compare persons
  with and without disability on levels of
  participation in employment, education, or family
  life to see if persons with disability have
  achieved social inclusion
• Monitor effectiveness of programs / policies to
  promote full participation can be monitored
• Monitor prevalence trends for persons with
  limitations in specific basic activity domains

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Work on Extended Measures

• The WG is reviewing disability questions from
  current instruments in order to form various
  recommended modules for different purposes
• Going in-depth on the same 6 domains as covered
  by the census questions
• Adding additional domains of functioning such as
  learning (especially for children), social
  interactions, and some of the other more complex
  activities listed in the ICF A/P classification.
• Asking about participation
• Asking questions on environmental factors.