# Presentation: 079578

## Measuring Disability in Canadian Questionnaires: A First Look

*Sally Kader*
*Health Statistics Division*
*Statistics Canada*

## Objectives

- To assess the differences in estimates of disability from filter (screening) questions in different surveys
- To examine the association between disability as measured by the filter questions and other measures of health or functional limitations

**Notes:**
 Assess:  the wording of the question, the context of the questionnaire and the placement of the question are all factors to consider.  These are available in the census, cchs, nphs, pals, gss and slid.

Filter questions are not the only way to estimate prevalence of disability.  Other health measures provide good indicators of its prevalence too.  These may include sph, adl and hui.  These are only available via cchs and nphs.

What is the trend that prevalence of disability following as time progresses.  Because of the need for several points over time, the rates are computed using cchs and nphs only.  Important to keep in mind that the questions used to estimate the rates have changed after 1998.

## Surveys with disability questions

**Census**
**Health Surveys: ***Canadian Community Health Survey (CCHS), National Population Health Survey (NPHS)*
**Post-Censal Surveys: ***Participation and Activity Limitations Survey (PALS), Aboriginal Peoples Survey (APS)*
**Labour Surveys: ***Labour Force Survey (LFS), Survey of Labour and Income Dynamics (SLID), Workplace and Employee Survey*
**Other Surveys: ***National Longitudinal Survey of Children and Youth, General Social Survey (GSS)*

**Notes:**
This slide provides a summary of the different surveys that contain the disability filter questions.  These are not the sources of data for this presentation.  The sources of data for this presentation are a subset of the ones here and are listed in the next slide.

## Sources of data

- Health
*2000 CCHS*
*1998 NPHS*
*1996 NPHS*

- Non-health
*2001 Census*
*1999 SLID*
*2000 GSS*

**Notes:**
Data from the slid and the gss have not been analyzed here, but in the concerned divisions.  We were able to obtain these numbers through the help of Renée from HFSSD.  They are used for comparison only.

## Filter questions: Census prior to 2001 

*Is this person limited in the kind or amount of activity he/she can do because of a long-term physical condition, or mental condition or a health problem:*
- ...at home?
- ...at school or at work?
- ...in other activities, for example, in transportation to and from work, or in leisure time activities?
*Does this person have any long-term disabilities or handicaps?*
_*Responses*_
- No, not limited
- Yes, limited* *

## Do you have any difficulty hearing, seeing, communicating, walking, climbing stairs, bending, learning or doing any similar activities?
Does a physical condition or mental condition or health problem reduce the amount or the kind of activity you can do
... at home?
...at work or at school?
...in other activities, for example, transportation or leisure?
Responses
Yes, often
Yes, sometimes
No, never

*Does a physical condition or mental condition or health problem reduce the amount or the kind of activity you can do*
- ... at home?
- ...at work or at school?
- ...in other activities, for example, transportation or leisure?
_*Responses*_
- Yes, often
- Yes, sometimes
- No, never

***Filter questions: ******Census 2001****** ***

**Notes:**
GSS has the long term qualifier but merges the last three questions.

Slid has the census wording.

## Prevalence of population identified as “disabled”, by survey

**Notes:**
Special effort was made to make the samples as comparable as possible.  The PALS is the survey with the most exclusions, so I attempted to exclude the same groups from the other surveys as well, whenever possible.

Except for CCHS, all other surveys produce rates that are within +/- 5% of the rate produced by the census.  Generally, rates range from 13.5% to 21.0%

## Self-perceived health (SPH)
NPHS and CCHS only 
A global evaluation of one’s health on a 5-point scale.
Response categories: “excellent”, “very good”, “good”, “fair” or “poor.”
Indicator scored as 1 if response is “fair” or “poor.”

- NPHS and CCHS only
- A global evaluation of one’s health on a 5-point scale.
- Response categories: “excellent”, “very good”, “good”, “fair” or “poor.”
- Indicator scored as 1 if response is “fair” or “poor.”

***Selected health status measures***

## Selected health status measures

- Health Utilities Index (HUI)
- NPHS and CCHS only
- A set of 30 questions covering 8 components: vision, hearing, speech, mobility, dexterity, pain, emotion, cognition.
- Each component has 2 levels: none/mild and moderate/severe.
- Indicator scored as 1 if response indicates moderate/severe impairment in any component.

**Notes:**
HUI: single attribute versus multiple attribute utility function.  Component scores range from 0 to 6, score weights range from 0.4 to 1.0.  Multiple attribute utility function scale ranges from 0 (death) to 1 (perfect health).  The HUI variable used here is a count of the number of components under which the individual was identified as disabled.  An individual was identified as disabled under any one component if the severity of their limitation is moderate or worse.

SPH: it is a question that has five possible answers excellent/very good/good/fair/poor.  An individual was identified as limited if they indicated fair or poor health.

ADL: These are questions that refer to activities of daily living and instrumental activities of daily living.  They involve assessing independence in personal care, house work, meal preparation, chores, grocery shopping, etc.  A respondent is dependent if they need help with any one or more of these activities.

## Activities of daily living (ADL and IADL)
NPHS and CCHS only 
A set of 6 questions about needing help in preparing meals, shopping for groceries or other necessities, housework, heavy chores, personal care, moving inside house.
Response categories: Yes/No.
Indicator scored as 1 if “Yes” response to any of the questions.

- NPHS and CCHS only
- A set of 6 questions about needing help in preparing meals, shopping for groceries or other necessities, housework, heavy chores, personal care, moving inside house.
- Response categories: Yes/No.
- Indicator scored as 1 if “Yes” response to any of the questions.

***Selected health status measures***

## Prevalence under disability filter questions and selected health status measures

**Notes:**
All measures are tracking together.  The only point that distinguishes itself from the trend is the CCHS filter questions data point.  Even though there was an increase in the prevalence of disability between 1998 and 2000, the CCHS rate of 31.1% from the filter questions seems to stand above all the other rates.

## Defining disagreement between filter questions and selected health status measures

- False negatives
- No to all the filter questions
- A positive score on another health measure
- False positives
- Yes to at least one of the filter questions
- A zero score on health measure under consideration

## Adjusted prevalence
NPHS and CCHS only
Exclude false positives
Estimate prevalence based on filter questions only

- NPHS and CCHS only
- Exclude false positives
- Estimate prevalence based on filter questions only

***Method used to adjust prevalence estimates of disability***

## Percentage of disagreement between filter questions and other selected health status measures

**Data Source:** NPHS 1996

**Notes:**
False negatives: persons having no disability under the filters but have classified themselves as disabled under other health measures.

False positives: persons having a disability under the filters but none under other health measures.

Adjusted rate: prevalence of disability recomputed after excluding people with false positives from the analysis.

## Percentage of disagreement between filter questions and other selected health status measures

***Percentage of disagreement between filter questions and other selected health status measures***

## Percentage of disagreement between filter questions and other selected health status measures

***Percentage of disagreement between filter questions and other selected health status measures***

## Summary

- As expected, the redesigned filter questions yield higher estimates of  the prevalence of disability than do former filter questions or other measures of health or functional limitation.
- CCHS estimates of prevalence of disability, based on the redesigned filter questions, are higher than those obtained from other surveys

## CCHS: Higher rates

- Possible explanations:
*New questions*
*Question placement*
*Proxy rates*
*Larger percentage of respondents choosing “sometimes” *
*Health context*

**Notes:**
Health Context: all the questions talk about health so people are more attune to health and functional issues than in other contexts

Questions are not at the beginning of the questionnaire, but fall after several questions about general health and contact with health professionals and hospitalization. People are already thinking about their health in general and what is wrong with it in particular.  Thus are more likely to capture higher portion of sample

The questions were changed after 1998.  The old questions were more limited to the handicap approach rather than the functional limitation approach.  A lot of groups were not captured because of that.  It was the objective to change the questions to broader ones that would allow for a wider sample base.

## Limitations

- Proxy reporting rates vary
- Method of questionnaire administration (in-person, telephone or self-completed)

**Notes:**
Between Surveys.  This discussion involves two issues: the comparability of the questions and the comparability of the samples.  Questions are highly comparable across surveys from 1999 onwards.  However, they are not identical.  Whereas CCHS and GSS drop the YES/NO part, they add the “long-term” qualifier.  

Samples were not identical either in terms of excluded subgroups of population.  All of PALS, CCHS and NPHS exclude people in collective dwellings, the armed forces, on reserve, crown lands and institutions.  The PALS also excludes certain aboriginal communities that participated in the APS and persons under 15 years of age.  GSS and SLID numbers were computed based on samples comprable to that of the PALS.  Samples of CCHS and the CENSUS were also adjusted to exclude the mentioned populations.  NPHS data did not have the necessary identifiers to make the exclusions so it will not be compared with surveys other than CCHS.  All surveys exclude territories and persons under 15 years of age.

Over time analysis is only possible for CCHS and NPHS.  Comparisons over time are harder to make.  The questions have changed to capture a wider disabled population (milder and non-physical disabilities) and the answer choices have changed.from Yes/No to those that reflect frequency and/or severity.

## Next steps

- Evaluate the possible effects of:
*Health context of survey*
*Proxy reporting*
*Method of questionnaire administration **(in-person, telephone or self-completed)*
*Question placement in survey*
*Short time span*