Key Collaborators
Mortality Among Very Low Birthweight Infants
in Hospitals Serving Minority Populations
• Jeanette Rogowski, Ph.D., University of Medicine and
Dentistry of New Jersey and RAND
•
•
•
•
•
Leo Morales, M.D., Ph.D.
Assistant Professor, UCLA
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
AcademyHealth
June 7, 2004
Support Provided by: UCLA-Drew EXCEED Program (AHRQ), RWJ Minority
Medical Faculty Development Program, and UCLA-RCMAR Center (NIA)
Morales-2 03/18/04
Hospital Characteristics and
Patient Outcomes
I. BACKGROUND
• 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
Morales-3 03/18/04
Trends in Infant Mortality
Morales-4 03/18/04
Very Low Birthweight Infants
• Overall, infant mortality is decreasing for black and
white infants
• Definitions
– Low birthweight (LBW): <2500 grams
• However, the disparity between black and white
infant mortality remains constant and maybe
increasing (MacDorman, 2002)
– Very low birthweight (VLBW): <1500 grams
• Small but high risk infant population
– 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
– 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)
one of six target areas in the Health People 2010
initiative
Morales-5 03/18/04
Morales-6 03/18/04
1
Research Questions
II. METHODS
• 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?
Morales-7 03/18/04
Primary Data Source
Morales-8 03/18/04
Additional Data Sources
• 1995-2000 Vermont Oxford Network (VON)
• American Hospital Association Annual Survey of
Hospitals
– 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
– Hospital characteristics
• 1990 United States Census
– Maternal income and education
Morales-9 03/18/04
Study Subjects
Morales-10 03/18/04
Outcome Variable
• VLBW infants between 500g and 1500g
• Neonatal mortality
– White infants (n= 49,132)
– Mortality in the first 28 days after birth
– Black (n=24,918)
– Mortality ascertained through transfers until
discharge home
• Inborn infants only
Morales-11 03/18/04
Morales-12 03/18/04
2
Main Explanatory Variable:
Hospital Minority-Serving Status
Explanatory Variables:
Case-Mix Variables
• 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%
•
•
•
•
•
•
•
•
•
•
•
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
Morales-13 03/18/04
Explanatory Variables:
Hospital Variables
Morales-14 03/18/04
Explanatory Variables:
Process of Care Variables
• Geography
• Indicator variables:
– 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
– Treatment with surfactants
– Treatment with antenatal steroids
Morales-15 03/18/04
Statistical Models
Morales-16 03/18/04
Estimation Methods
• 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
Morales-17 03/18/04
• Maximum-likelihood logistic regression models
• Robust standard errors
• Clustering of infants within hospitals
• STATA 8.0
Morales-18 03/18/04
3
Infants by Case-Mix Variables
III. RESULTS
All Infants
(n=74,050)
Neonatal Infant Morality
11%
Birth Weight (grams)
1048.5
Gestational Age (weeks)
1
28.5
M
inute 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%
Morales-19 03/18/04
Morales-20 03/18/04
Stratified Logistic Regressions:
Neonatal Mortality on Case-Mix Variables
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)
White Infants
Odds Ratio
31%
36%
33%
53%
Black Infants
95% CI
Odds Ratio
95% CI
Minority-Serving Status
19%
27%
37%
16%
8%
28%
<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
Vaginal Delivery
11%
83%
7%
48%
16%
11.7
1.00
16.50
1.36
(14.46 – 18.82)**
(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
Morales-21 03/18/04
Morales-22 03/18/04
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 2
Odds Ratio
95% CI
Model 3
Odds Ratio
95% CI
(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)
(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
(1.12 - 1.49)**
1.00
1.27
(1.10 - 1.46)**
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)**
1.00
(0.98 - 1.27)
1.11
(1.10 - 1.50)** 1.25
1.10
1.00
1.09
1.05
1.21
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
Note. Models include case-mix model and year dummies. *p<0.05 **p<0.01
Morales-23 03/18/04
Morales-24 03/18/04
4
Thought Expereiment-2
IV. CONCLUSIONS
• 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
Morales-25 03/18/04
Morales-26 03/18/04
Conclusions
Implications
• Minority-serving hospitals had higher neonatal
• Minority-serving hospitals may provide worse
mortality than other hospitals
quality of care than other hospitals
• The difference in neonatal mortality between
• Hospital-level factors may be more important in
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
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
Morales-27 03/18/04
Morales-28 03/18/04
Potential Explanations for Results
Contact Information:
• Staffing patterns
– Nurse-to-patient ratio
morales@rand.org
or
310-794-2296
– 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
Morales-30 03/18/04
5
Study Generalizability
Hospital Characteristics
All
(n=74,050)
• Compared with all US hospitals, VON hospitals are:
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)
– 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
Morales-31 03/18/04
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
Morales-32 03/18/04
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
Morales-33 03/18/04
6