Exploring The Determinants Of Racial &
Ethnic Disparities In Total Knee Arthroplasty:
Health Insurance, Income And Assets
Amresh Hanchate, PhD
Health Care Research Unit
Boston University School of Medicine
AcademyHealth
Annual Research Meeting 2006
June 25, 2006
Collaborators
• Arlene Ash, PhD
Health Care Research Unit
Boston University School of Medicine
• Yuqing Zhang, PhD & David T. Felson, PhD
Clinical Epidemiology & Research Training
Boston University School of Medicine
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Disparities in TKA by race/ethnicity
Table 1. Mean TKA rate per 1,000 Medicare enrollees per year
(1998-2000)
TKA rate / 1,000
% of White
Women
White
5.97
100%
Black
4.94
83%
Hispanic
5.37
90%
Men
White
4.82
100%
Black
1.84
38%
Hispanic
3.46
72%
Source:
Skinner, Jonathan et al (2003), “Racial, Ethnic, and Geographic Disparities in Rates of Knee Arthroplasty among
Medicare Patients”, NEJM
• Relative to whites, TKA rates lower among blacks & Hispanics
• Remarkably lower TKA rates among black men
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Affordability & TKA Disparities
Objective:
To investigate the role of indicators of affordability.
•
Estimate TKA rates associated with
•
•
•
•
comprehensiveness of insurance coverage
household income
household assets
After adjusting for affordability, we estimate the size of
residual disparities (by race/ethnicity) in TKA
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Data
Health & Retirement Study
Institute of Social Research, University of Michigan
• Offers a very rich array of data covering health, demographic and
economic domains
• Nationally representative of persons born in 1947 or earlier
• Consists of 4 distinct birth cohorts – two of which surveyed prior to
1998 – but all pooled in 1998 and surveyed biennially with a common
survey instrument
• This study starts with 19,983 persons in the 1998 survey round and
follow through 2000 and 2002 rounds
• Final sample of 18,376 after excluding 1,597 persons who
• had prior (pre-1998) history of TKA
• were not White (non-Hispanic) / Black (non-Hispanic) / Hispanic
• had incomplete covariate data
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Measures
Outcome:
Binary (1/0) indicator of whether respondent had first TKA,
because of arthritis, in the survey period
•
•
•
•
Each round respond to: Have you had a TKA in the last two years?
Maximum of 3 records per person (6 years of total exposure)
If TKA reported then subsequent rounds excluded
If death after 1998 then subsequent rounds excluded
Affordability indicators
–Health insurance:
1) No insurance
4) Medicare FFS only
7) Medicare + Medicaid
2) Private
5) Medicare FFS + private
3) Medicaid
6) Medicare HMO
–Household Income (1993 $)
–Non-housing assets (1993 $)
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Other Covariates
Adjust for differences in need as in Dunlop et al (2003, Medical Care)
• Demographics
– Gender, age, education, race & ethnicity
• Health conditions
– Ever had
• 1) Heart disease, 2) lung disease, 3) cancer, 4) hypertension, 5) diabetes
– Whether has difficulty in
• 1) walking one block, 2) getting up from a chair, 3) climbing one flight of
stairs, 4) stooping or crouching
• Geographic regions (10)
Estimation
Logistic Random Effects Regression
• Lagged (one-period) covariates
• Sampling weights used to adjust for over-sampling of non-whites
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Table 2. Study Sample & TKA Counts
(Health & Retirement Study, 1998-2002)
# Persons
Women
White, Non-Hispanic
Black, Non-Hispanic
Hispanic
Men
White, Non-Hispanic
Black, Non-Hispanic
Hispanic
Total
# Observations
# persons with
TKA in study
period
7,997
1,586
796
18,499
3,645
1,824
247
46
17
6,405
983
609
18,376
14,785
2,205
1,378
42,336
167
10
7
494
• Average of 2.2 records per person – same across all race & ethnicity groups
– about 4.5 years of exposure period
• 44% of observations are for ages 64 or younger
• 32% of TKAs at age 64 or younger
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Table 3. Unadjusted & Adjusted TKA Rates & Odds Ratios (OR)
(Health & Retirement Study, 1998-2002)
Adjusted for
Adjusted also for
Unadjusted
Demographics + Health
Affordability Indicators
Status
Mean rate
OR
/1,000 persons OR relative OR relative
95% CI relative to
95% CI
/year
to white
to white
white
Women
White
Black
Hispanic
Men
White
Black
Hispanic
6.5
6.9
4.5
1.00
1.06
0.68
1.00
0.80
0.69
[0.56, 1.15]
[0.40, 1.18]
1.00
0.96
0.96
[0.66, 1.40]
[0.55, 1.68]
5.4
2.1
2.4
1.00
0.38
0.44
1.00
0.32
0.49
[0.15, 0.66]
[0.22, 1.06]
1.00
0.39
0.64
[0.19, 0.81]
[0.29, 1.42]
• Compared to whites, TKA rates are lower among Hispanics and black men
• Higher rate among black women – most of this occurs when 64 or younger
• Adjusting for need based on health status increases rate-gap among blacks
& marginally reduces rate-gap among Hispanics
• Further adjusting for affordability indicators significantly rate-gap among
blacks and Hispanics – large gaps remain for non-white men
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Table 4. Affordability Indicators & TKA Odds Ratio (OR)
(Health & Retirement Study, 1998-2002)
Affordability Indicator
OR
95% CI
Health insurance access (%)
Reference
Medicare FFS Only
Medicare with Private
1.30
[0.99, 1.70]
Medicare with Medicaid
1.73
[1.09, 2.73]
Medicare HMO Only
1.49
[1.05, 2.10]
Private
1.01
[0.66, 1.55]
0.71
[0.41, 1.22]
Uninsured
Medicaid only
1.41
[0.90, 2.20]
Household income
< $10k
0.73
[0.54, 0.98]
$10k - 20k
0.78
[0.62, 0.98]
$20k+
Reference
Household assets
< $5k
0.72
[0.54, 0.96]
$5k - 20k
0.88
[0.67, 1.15]
$20k+
Reference
• Among 65+, compared to those with Medicare FFS only, probability of TKA
among those with more comprehensive coverage it is at least 32% higher
• Among 64 or younger, probability of TKA almost 30% lower among insured
compared to those insured
• Lower income/assets, lower TKA probability
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Table 5. Affordability Indicators by Race & Ethnicity
White
Black
Hispanic
White
Black
Hispanic
(Health & Retirement Study, 1998-2002)
% with
% with no
Medicare % with
% with
insurance
FFS only income < assets <
among
among
$10k
$5k
under 65
over-65
Women
18
36
17
16
19
36
49
58
37
25
52
57
Men
14
33
9
11
16
34
31
44
33
26
42
47
• Among 64 or younger, uninsured % for Hispanics double that for whites
• But among 65+, larger % of Hispanics have comprehensive coverage
• Higher % blacks and Hispanics with low income & assets
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Conclusions
• Adjusting for need, blacks and Hispanics have
significantly lower TKA rates compared to whites
• Among women, adjusting for affordability
indicators leaves no residual TKA disparities
• Among men, a large gap remains even after
adjusting for affordability indicators – particularly
among black men
• Limitations
– Some loss of accuracy – recall data
– Some loss of representativeness - attrition due to loss to follow up
– Absence of data on out-of-pocket expenditures and more detailed
clinical information on need for TKA
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