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The Definition and Measurementof DisabilityThe Work of the Washington Group on Disability Statistics

Jennifer H. MadansNational Center for Health Statistics, USAfor the Washington Group on Disability Statistics

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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

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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

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Global disability prevalence rates*

High-income countries Low-income countries

Year % Year %

Canada 1991 14.7 Kenya 1989 0.7

Germany 1992 8.4 Namibia 1991 3.1

Italy 1994 5.0 Nigeria 1991 0.5

Netherlands 1986 11.6 Senegal 1988 1.1

Norway 1995 17.8 South Africa 1980 0.5

Sweden 1988 12.1 Zambia 1990 0.9

Spain 1986 15.0 Kenya 1989 0.7

UK 1991 12.2 Zimbabwe 1997 1.9

USA 1994 15.0 Malawi 1983 2.9

* Sources and methodologies are country specific

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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

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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

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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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Health Condition(disorder/disease)

Body Function &Structure (Impairment)

Activities(Limitation)

Participation(Restriction)

EnvironmentalFactors

PersonalFactors

Source: World Health Organization, 2001

The ICF Model

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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

• Source of data can impact choice of purpose and definition

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Purpose of Data Collection3 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

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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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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

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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

Example: Monitoring trends in functioning

• Information is used to characterize population functioning

• Focus on the interaction of people and environment

0

5

10

15

20

25

Pro

port

ion (

%)

2005 2010 2015 2020 2025

Population reporting limitation in work

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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

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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.

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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 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)

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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

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Health Condition(disorder/disease)

Body Function &Structure (Impairment)

Participation(Restriction)

EnvironmentalFactors

PersonalFactors

Source: World Health Organization, 2001

Locating Risk in the ICF Model

?

Example: Equalization of opportunities

• Compares actual participation by level of risk for limitations in activity or participation

• Disability used as a demographic

% Employed

0

30

60

90

Pro

port

ion (

%)

Nondisabled Disabled

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Criteria for inclusion of domains

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

modes

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Possible question optionsMobility• Walking• Climbing stairs• Bending or stooping• Reaching or lifting• Using handsSensory• Seeing• HearingCommunicating• Understanding• Speaking

Cognitive functions• Learning• Remembering• Making decisions• ConcentratingEmotional functioning• Interpersonal interactions• Psychological well-being

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WG short set of questions for censuses:Because of a Health problem:1) Do you have difficulty seeing even if wearing glasses?2) Do you have difficulty hearing even if using a hearing

aid?3) Do you have difficulty walking or climbing stairs?4) Do you have difficulty remembering or concentrating?5) Do you have difficulty with (self-care such as) washing

all over or dressing?6) 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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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

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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

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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

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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.

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RowVision (1) Hearing (1) Mobility

Communi-cation

Cognition/ remembering

Upper Body

Learning/ understanding

Affect Pain FatigueADL/ IADL

Getting Along with

People

Life Activities

Participation in Society

Short SetSingle Questions (1) d a d

Extended SetMultiple Questions (1) c c c c

Use of Assistive DevicesMicro-E (2)

Functioning with Assistance, Micro-E (2)

5 Age at Onset

6 Cause

7 Duration

8 Impact ? ? ?

9Meso-Environment

(3)

10Macro-Environment

(4)

ICF Chapter Reference - Activities/Participation

ICF-1 ICF-1 ICF-4 ICF-3 ICF-1,2 ICF-4 ICF-1 ICF-2 ICF-5,6 ICF-7 ICF-8 ICF-9

Capacity Perform

ance

Basic Activity Domains Complex Activity Domains

(5) See Note below

Washington Group/Budapest Initiative/UNESCAP Activities and Workplan

QuestionnaireTopic/Type

To be obtained through other sources, not personal survey data collections

b