Mortality Among Very Low Birthweight Infants
in Hospitals Serving Minority Populations
Leo Morales, M.D., Ph.D.
Assistant Professor, UCLA
AcademyHealth
June 7, 2004
Support Provided by: UCLA-Drew EXCEED Program (AHRQ), RWJ Minority
Medical Faculty Development Program, and UCLA-RCMAR Center (NIA)
Key Collaborators
• Jeanette Rogowski, Ph.D., University of Medicine and
Dentistry of New Jersey and RAND
•
•
•
•
•
Douglas Staiger, Ph.D., Dartmouth University
Jeffery Horbar, M.D., The Vermont Oxford Network (VON)
Joe Carpenter, M.S., VON
Mike Kenny, M.A., VON
Jeff Geppert, M.A., National Bureau of Economic Research
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I. BACKGROUND
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Hospital Characteristics and
Patient Outcomes
• Worse outcomes are associated with:
– Rural hospitals (Kahn, 1994)
– Non-teaching hospitals (Kuhn, 1994; Polanczyk, 2002;
Taylor, 1999; Kahn, 1994)
– For-profit hospitals (Hartz, 1989; Haas, 2003)
– Lower expenses per admission (Burstin, 1993)
– Minority-serving hospitals (Brennan, 1991)
– Low volume and lower level of care (Phibbs, 1996)
• Little is known about the relationship of minorityserving hospital status to infant mortality
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Trends in Infant Mortality
• Overall, infant mortality is decreasing for black and
white infants
• However, the disparity between black and white
infant mortality remains constant and maybe
increasing (MacDorman, 2002)
– Black infant mortality 14.1 per 1,000 live births
– White infant mortality 5.7 per 1,000 live births
• Eliminating the racial disparity in infant mortality is
one of six target areas in the Health People 2010
initiative
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Very Low Birthweight Infants
• Definitions
– Low birthweight (LBW): <2500 grams
– Very low birthweight (VLBW): <1500 grams
• Small but high risk infant population
– LBW infants account for 7.6% of live births but
66% of all infant deaths (MacDorman, 2002)
– VLBW infants account for 1.4% of live births but
52% of all infant deaths (MacDorman, 2002)
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Research Questions
• Do VLBW infants treated by minority-serving
hospitals have similar neonatal mortality as those
treated by other hospitals?
• Do hospital characteristics and process of care
variables explain differences in neonatal mortality
between minority-serving hospitals and other
hospitals?
• Are black and white infants treated by minorityserving hospitals at similar risk for neonatal
mortality?
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II. METHODS
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Primary Data Source
• 1995-2000 Vermont Oxford Network (VON)
– 332 hospitals
– 40% of US hospitals with NICUs
– 50% of VLBW infants in US
• Abstracted medical records
– Mortality outcomes
– Case-mix variables
– Process of care
• Institutional survey of participating hospitals
– NICU level of care
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Additional Data Sources
• American Hospital Association Annual Survey of
Hospitals
– Hospital characteristics
• 1990 United States Census
– Maternal income and education
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Study Subjects
• VLBW infants between 500g and 1500g
– White infants (n= 49,132)
– Black (n=24,918)
• Inborn infants only
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Outcome Variable
• Neonatal mortality
– Mortality in the first 28 days after birth
– Mortality ascertained through transfers until
discharge home
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Main Explanatory Variable:
Hospital Minority-Serving Status
• Hospitals assigned to 1 of 3 categories based on the
proportion of infants treated between 1995 and 2000 who were
Black
• % VLBW black infants = VLBW black infants / VLBW black and
white infants
Category
Number of
Hospitals
Proportion of
Hospitals
<15% Black Infants
113
34%
15%-35% Black Infants
121
36%
>35% Black Infants
98
30%
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Explanatory Variables:
Case-Mix Variables
•
•
•
•
•
•
•
•
•
•
•
Gestational age (+ gestational age squared)*
Birthweight*
Small for gestational age
Congenital malformation
Multiple birth
Any prenatal care
1-minute APGAR
Sex
Race
Vaginal delivery
Maternal income and education based on census
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Explanatory Variables:
Hospital Variables
• Geography
– Region
– Urban setting of >1,000,000
• NICU characteristics
– Level of care
– Volume
• Hospital characteristics
– Ownership
– Teaching status
– Percent Medicaid admissions
– Expenditures per admission
– Average maternal income and education based on census
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Explanatory Variables:
Process of Care Variables
• Indicator variables:
– Treatment with surfactants
– Treatment with antenatal steroids
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Statistical Models
• Descriptive analysis
– Infants by case-mix, hospital, and process of
care variables
• Stratified regression by race
– %black + case-mix
• Pooled regression
– Model 1: %black + case-mix
– Model 2: %black + case-mix + hospital
– Model 3: %black + case-mix + hospital +
process of care
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Estimation Methods
• Maximum-likelihood logistic regression models
• Robust standard errors
• Clustering of infants within hospitals
• STATA 8.0
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III. RESULTS
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Infants by Case-Mix Variables
All Infants
(n=74,050)
Neonatal Infant Morality
Birth Weight (grams)
11%
1048.5
Gestational Age (weeks)
28.5
1-Minute APGAR Score
5.4
Male Sex
51%
Small for Gestational Age
21%
Multiple Birth
29%
Congenital Malformation
4%
Vaginal Delivery
38%
Maternal Black Race
34%
Had Prenatal Care
96%
Maternal Education (years)
12.41
Maternal Income ($1000s)
36.01
Antenatal Steroids
74%
Surfactants
60%
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Infants by Hospital Variables
All Infants
(n=74,050)
Minority Serving Status
<15%
15% to 35%
>35%
Urban Hospital
Region
Northeast
Midwest
South
West
Volume <40 Infants per Year
Level C NICU
Hospital Ownership
Government
Not For-Profit
For-Profit
Member, Council of Teaching Hospitals
Percent Medicaid Admissions
Expense per Hospital Admission ($1000s)
31%
36%
33%
53%
19%
27%
37%
16%
8%
28%
11%
83%
7%
48%
16%
11.7
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Stratified Logistic Regressions:
Neonatal Mortality on Case-Mix Variables
White Infants
Odds Ratio
95% CI
Black Infants
Odds Ratio
95% CI
Minority-Serving Status
<15% Black Infants
1.00
15%-35% Black Infants
1.10
(0.97 – 1.27)
1.16
(0.91 – 1.47)
>35% Black Infants
1.30
(1.09 – 1.56)**
1.29
(1.01 – 1.64)*
Gestational Age
0.04
(0.04 – 0.53)**
0.04
(0.03 – 0.50)**
Gestational Age Squared
1.05
(1.05 – 1.05)**
1.05
(1.05 – 1.06)**
1-Minute APGAR Score
0.73
(0.71 – 0.74)**
0.75
(0.72 – 0.77)**
Small for Gestational Age
2.44
(2.14 – 2.77)**
2.28
(1.93 – 2.69)**
Multiple Birth
1.32
(1.20 – 1.45)**
1.22
(1.07 – 1.39)**
14.74
(11.48 – 18.9)**
Congenital Malformation
16.50
1.00
(14.46 – 18.82)**
Vaginal Delivery
1.36
(1.25 – 1.49)**
1.36
(1.21 – 1.52)**
Prenatal Care
0.94
(0.77 – 1.15)
0.85
(0.72 – 1.01)
Maternal Income
1.00
(1.00 – 1.01)
1.00
(0.99 – 1.01)
Maternal Education
1.01
(0.95 – 1.06)
0.99
(0.93 – 1.07)
Male
1.25
(1.17 – 1.34)**
1.28
(1.15 – 1.43)**
Note. Models include year dummies. *p<0.05 **p<0.01
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Pooled Regressions:
Neonatal Mortality on Hospital and Case-Mix Variables
Model 1
Odds Ratio
Minority-serving Status
0-15% Black Infants
1.00
15-35 Black Infants
1.12
>35% Black Infants
1.28
Urban Setting
Regional Location
Northeast
Midwest
South
West
NICU Volume
?40 Infants
<40 Infants
Level of Care
Levels A and B
Level C
Hospital Ownership
Private Not-For-Profit
Private For-Profit
Government
Teaching Hospital
% Medicaid Admissions
Expenses per Admission ($1000s)
Average Education (Hospital
Level)
Average Income (Hospital Level)
Treatment with Antenatal Steroids (Infant Level)
Treatment with Surfactants (Infant Level)
95% CI
Model 3
Odds Ratio
95% CI
1.00
(0.98 - 1.27)
1.11
(1.10 - 1.50)** 1.25
1.10
(0.98 - 1.27)
(1.04 - 1.51)*
(0.98 - 1.23)
1.00
1.11
1.26
1.10
(0.98 - 1.27)
(1.04 - 1.52)*
(0.97 - 1.24)
1.00
1.09
1.05
1.21
(0.90 - 1.31)
(0.90 - 1.23)
(1.00 - 1.45)*
1.00
1.09
1.05
1.19
(0.89 - 1.32)
(0.90 - 1.24)
(0.98 - 1.44)
1.00
1.29
1.00
(1.12 - 1.49)** 1.27
1.00
0.86
(0.76 - 0.98)*
1.00
0.86
(0.76 - 0.98)*
1.00
0.83
1.07
1.02
1.04
1.01
0.91
(0.67 - 1.02)
(0.91 - 1.26)
(0.91 - 1.15)
(0.55 - 1.97)
(0.99 - 1.02)
(0.80 – 1.03)
1.00
0.79
1.07
1.03
0.96
1.01
0.95
(0.65 - 0.95)*
(0.90 - 1.26)
(0.91 - 1.17)
(0.51 - 1.84)
(0.99 - 1.03)
(0.83 - 1.09)
1.00
(0.99 – 1.02)
1.00
0.54
0.56
(0.98 - 1.01)
(0.50 - 0.58)**
(0.50 - 0.62)**
95% CI
Model 2
Odds Ratio
(1.10 - 1.46)**
Note. Models include case-mix model and year dummies. *p<0.05 **p<0.01
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Thought Experiment-1
• What if black infants were treated by the three categories of
hospitals we studied (e.g., <15% black, 15% to 35% black,
>35% black) in the same proportions as white infants?
– Black infant mortality would drop by 8.5%
100%
80%
60%
<15%
15%-35%
>35%
40%
20%
0%
White Infants
Black Ifants
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Thought Expereiment-2
• What if neonatal mortality at hospitals where 15%
or more of the treated infants were black were the
same as hospitals where <15% of the infants
treated were black?
– 10% lower for white infants
– 22% lower for black infants
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IV. CONCLUSIONS
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Conclusions
• Minority-serving hospitals had higher neonatal
mortality than other hospitals
• The difference in neonatal mortality between
minority-serving and other hospitals was not
explained by the hospital variables or process of
care variables
• Neonatal morality was similarly elevated for black
and white VLBW infants treated by minority-serving
hospitals
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Implications
• Minority-serving hospitals may provide worse
quality of care than other hospitals
• Hospital-level factors may be more important in
understanding disparities in care than individual
characteristics such as infant race per se, at least
among VLBW infants
• Disparities in infant mortality nationally might be
reduced by improving care for VLBW infants at
minority-serving hospitals
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Contact Information:
morales@rand.org
or
310-794-2296
Potential Explanations for Results
• Staffing patterns
– Nurse-to-patient ratio
– Board-certified specialists
• Maternal characteristics: smoking, drug and alcohol use
– Mediated by infant severity of illness
– Infant characteristics in minority-serving similar to other
hospitals
– Maternal income and education had no effect
• Unmeasured severity of illness
– VON risk adjustment ROC=0.88
– SNAP ROC=0.73 to 0.91
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Study Generalizability
• Compared with all US hospitals, VON hospitals are:
– More likely to be private non-profit
– Teaching hospitals
– Children’s hospitals
– More NICU beds
• Compared with all VLBW infants in US, VLBW
infants treated by VON hospitals are:
– Differed in terms of birthweight but not
gestational age
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Hospital Characteristics
All
(n=74,050)
Minority-Serving Status
<15% Black Infants
15% to 35% Black Infants
>35% Black Infants
Urban Hospital
Region
Northeast
Midwest
South
West
Volume<40 Admits per Year
Level C (Highest Level of Care)
Hospital Ownership
Government
Not For-Profit
For-Profit
Member, Council of Teaching Hospitals
Medicaid Admissions
Expense per Admission ($1000s)
White
(n=49,132)
Black
(n=24,918)
31%
36%
33%
53%
39%
43%
18%
48%
8%
35%
57%
64%
19%
27%
37%
16%
8%
28%
19%
29%
32%
20%
8%
30%
20%
23%
48%
10%
8%
24%
11%
83%
7%
48%
16%
11.7
9%
84%
7%
46%
15%
11.8
14%
80%
6%
52%
19%
11.4
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Secondary Analyses
• Do the effects of risk-adjustment vary by race?
– Insignificant case-mix*race interactions
• Do the effects of minority-serving status vary by race?
– Insignificant percent black*race interactions
• Do the effects of hospital variables vary by percentage
black infants treated?
– Insignificant percent black*hospital characteristic
interactions
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