The Definition and Measurement of Disability

1
The Definition and Measurementof Disability

• The Work of the Washington Group
• Mitchell Loeb
• National Center for Health Statistics, USA
• for the Washington Group on Disability Statistics

2
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

3
Current Problem

• Censuses use one of four types of questions that
  provide widely differing estimates of national
  prevalence of disability.
• The four types of questions include
• Generic questions about the presence of a
  condition
• Generic questions about the presence in the
  household of a person with a disability followed
  by a list of impairments
• Checklist of impairments
• Questions on functional domains

4
Variety in National Estimates

• Developing Countries
• Tunisia (1994) 1.2
• Pakistan (1981) 0.5
• Thailand (1990) 0.3
• Turkey (1985) 1.4
• Philippines (1995) 1.3
• Developed Countries
• Norway (1995) 17.8
• Spain (1986) 15.0
• United States (1994) 15.0

Data from surveys Source United Nations
Statistical Division
5
The WG was set up 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
• Develop extended set/s of items to measure
  disability on population surveys
• Address methodological issues associated with
  disability measurement

6
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

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
The ICF Model
Source World Health Organization, 2001
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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 a definition are chosen
• 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
Population reporting work limitation

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

13
Purpose Equalization of opportunities
Employed

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

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Locating Risk in the ICF Model
?
ACTIVITY
Source World Health Organization, 2001
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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
• 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)
• Connection between disability and participation
  can be made during data analysis

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Possible question options

• 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

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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 (short disability
measure)

• 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

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Objectives

• 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
• Represent commonly occurring limitations in
  domains that can be captured in the Census
  context
• Identify persons with similar problems across
  countries

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Objectives

• Compare levels of participation in employment,
  education, or family life for those with
  disability versus those without disability to see
  if persons with disability have achieved social
  inclusion
• Monitor prevalence trends for persons with
  limitations in specific basic action domains
• Emphasize that one measure will not satisfy
  multiple needs for disability data

21
Pre-testing activities

• Two regional workshops successfully implemented
• June 20-22, 2005 / Nairobi, Kenya
• September 19-20, 2005 / Rio de Janeiro, Brazil

22
Standardized testing

• 17 countries participating
• 13 funded via World Bank grant, 4 self-funded
• Cognitive tests in 13 countries
• Congo, Egypt, Gambia, India, Kenya, Lesotho,
  Mauritius, Philippines, Uganda, Mexico, South
  Africa, Tanzania, Vietnam
• Field tests in 4 countries
• Gambia, Vietnam, Sweden, Tanzania
• Combined cognitive/field test in 3 countries
• Argentina, Brazil, Paraguay

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Intended use of data

• Compare levels of participation in employment,
  education, or family 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
• Monitor prevalence trends for persons with
  limitations in specific basic activity domains

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Limitations

• One set of measures will not satisfy 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

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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.

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Meeting Products and More Information

• Executive summary of last seven meetings posted
  on the Washington Group website along with
  presentations / papers from the meetings
• http//www.cdc.gov/nchs/citygroup.htm
• Publication of key papers in a special issue of
  Research in Social Science and Disability