Are We There Yet?
Distance to Pediatric
Subspecialty Care in the US
Michelle L. Mayer, PhD, MPH
Research Assistant Professor
Department of Health Policy and Administration
and
Research Fellow
CG Sheps Center for Health Services Research
This work was funded by the Agency for Health Care Research and Quality
grant 1-K02-HS013309-01A1
Access to
Pediatric Subspecialty Care
• There is currently debate about the adequacy of
the pediatric subspecialty (PSS) workforce.
• To date, there are few studies that adequately
assess the availability of PSS care.
• We do know that the majority of PSS are highly
centralized in
– academic medical centers
– urban areas
Research Questions
• How far do children travel for PSS care?
• What county characteristics are associated
with greater distances to PSS care?
• What are the provider to population ratios
across pediatric subspecialties?
• How many children are needed to support
pediatric subspecialists?
Data Sources
• 2003 Diplomate File from the American Board of
Pediatrics
– Individual level file that contains gender, date of
medical school graduation, and certification and
expiration dates for all subspecialty certifications
• 2003 data from the Bureau of Health Professions’
Area Resource File
– County level composite file of data from multiple
sources
• 2003 population estimates from the Census
Bureau
Research Question 1
Distance to Care
• For each PSS, we calculated the straightline distance between each county in the
USA and the nearest provider.
• We merged pediatric population data to
distance data at the county level and
estimated
– population weighted average distance to care
– % of the under 18 population living within
selected distances of a provider
Table 1: Mean Population Weighted Distance to Care by PSS,
US Counties
Number of
Providers
Pediatric Subspecialty
Neonatal Perinatal Medicine
Cardiology
Hematology Oncology
Critical Care Medicine
Endocrinology
Pulmonology
Infectious Diseases
Allergy Immunology
Gastroenterology
Emergency Medicine
Nephrology
Adolescent Medicine
Developmental Behavioral Pediatrics
Rheumatology
Neurodevelopmental Pediatrics
Sports Medicine
3588
1503
1553
1013
889
627
838
514
712
1075
530
396
296
173
185
82
Population Weighted
Distance to Care, in Miles
Mean
75%ile 95%ile
13
20
59
19
29
83
24
30
90
24
35
92
24
37
95
28
39
106
29
38
102
29
36
106
30
39
106
33
45
123
34
46
142
40
54
140
42
60
145
58
75
221
71
85
208
77
101
240
Table 2: Percent of Under 18 Population Living within
Selected Distance by PSS, US Counties
Neonatal and Perinatal Medicine
Pediatric Cardiology
Pediatric Hematology/Oncology
Critical Care Medicine
Pediatric Allergy
Pediatric Endocrinology
Pediatric Infectious Disease
Pediatric Pulmonology
Pediatric Gastroenterology
Pediatric Emergency Medicine
Pediatric Nephrology
Adolescent Medicine
Development Behavioral Pediatrics
Pediatric Rheumatology
Neurodevelopmental Disabilities
Pediatric Sports Medicine
Percent of Under 18 Population
Within 50 Miles of a 100 or More Miles from
Provider
a Provider
92.9%
1.5%
87.5%
3.1%
85.8%
3.9%
83.8%
4.1%
83.6%
5.6%
82.1%
4.4%
81.5%
5.2%
81.4%
5.7%
81.3%
5.9%
77.2%
8.1%
76.6%
8.8%
73.1%
10.2%
70.9%
11.5%
64.6%
18.1%
58.5%
20.6%
53.0%
25.2%
Research Question 2
Identification of Areas Facing
Geographic Access Barriers
• Specialty-specific logit models
• Dependent Variable:
– Located 50 or more miles from a provider
• Independent Variables of Interest:
– Metropolitan Status (MSA)
– Census Division
• Models control for number of children under
18, per capita income, population density, and
sociodemographic characteristics of the
county
Counties “At-Risk” for
Geographic Access Barriers
• For all PSS, increased likelihood of being 50 or
more miles from a provider associated with
– Lower population density & smaller under-18 population
– In West North Central region
– In a non-metro area or MSA of less than 1 million people
• Counties in the Pacific and Mountain regions were
also at risk for a majority of specialties
• The presence of a COTH facility was associated
with a decreased risk for a handful of specialties
Research Question 3
Provider to Population Ratios
• For each PSS, we calculated
– Percent of MSA with one or more providers
– Mean provider to population ratios across all
MSA in the US
– Coefficient of variation
• MSA-level analysis used to allow for a
larger market area
Table 3: Provider to under-18
Population Ratios by PSS, MSA
Provider : Under-18
Population (in 100,000)
% with a
COV
Pediatric Subspecialty
Provider
Mean Std. Dev.
%
Adolescent Medicine
33
0.43
1.18
277
Critical Care Medicine
48
1.52
5.07
333
Developmental Behavioral Pediatrics
32
0.45
1.38
307
Neurodevelopmental Disabilities
21
0.19
0.55
287
Neonatal Perinatal Medicine**
76
10.57
24.40
231
Allergy
51
1.00
2.64
265
Cardiology
60
2.16
4.59
212
Endocrinology
48
1.35
6.76
501
Infectious Diseases
44
1.10
4.47
407
Pulmonology
43
1.03
4.26
413
Emergency Medicine
40
1.08
3.13
290
Gastroenterology
46
0.91
2.02
223
Hematology Oncology
53
1.91
4.71
246
Nephrology
35
0.68
1.88
275
Rheumatology
23
0.22
0.69
315
Sports Medicine
16
0.14
0.53
387
* Statistics calculated at the state level using data from non-metropolitan counties only
** Ratio cacluated using number of births in the county
Research Question 4
Population Thresholds
• For each PSS, we used ordered logit used to
predict
– population needed to support a single PSS, and
– population increments needed to support additional
providers.
• MSA-level analysis used to allow for a larger
market area
• Dependent Variable
– Number of providers in the MSA
Figure 1: Predicted Population Threshold Needed to
Support a Single Provider by PSS, MSA
Pediatric Sports Medicine
Neurodevelopmental Disabilities
Pediatric Rheumatology
Pediatric Subspecialty
Developmental Behavioral Pediatrics
Adolescent Medicine
Pediatric Nephrology
Pediatric Emergency Medicine
Pediatric Pulmonology
Pediatric Infectious Diseases
Pediatric Gastroenterology
Pediatric Endocrinology
Critical Care Medicine
Pediatric Allergy
Pediatric Hematology Oncology
Pediatric Cardiology
0
100,000
200,000
300,000
400,000
500,000
600,000
Predicted Pediatric Population Threshold
95% Confidence Interval
700,000
800,000
Figure 2: Population Increments Needed to
Support Additional Providers in an MSA,
Non-procedural Subspecialties
Pop'n < 18
700,000
600,000
Neurodevelopmental
Disabilities
Rheumatology
500,000
Allergy Immunology
400,000
Dev't Behavioral
300,000
Infectious Diseases
200,000
Adolescent Medicine
100,000
Endocrinology
Hematology Oncology
0
1
2
3
Provider
4
5
Figure 3: Population Increments Needed to Support
Additional Providers in an MSA,
Procedural & Intensivist Subspecialties
700,000
600,000
Pop'n < 18
500,000
Pulmonology
Gastroenterology
Critical Care Medicine
Emergency Medicine
Cardiology
400,000
300,000
200,000
100,000
0
1
2
3
Providers
4
5
Figure 4: Population Increments Needed to Support
Additional Providers in an MSA,
Procedural & Intensivist Subspecialties
200,000
150,000
Pop'n < 18
Pulmonology
Gastroenterology
Critical Care Medicine
100,000
Emergency Medicine
Cardiology
50,000
0
1
2
3
Providers
4
5
Discussion
Discussion
• There is considerable variation in the
population weighted distance to care across
pediatric subspecialties.
• For most PSS, more than three-quarters of
the under-18 population lives within 50
miles of a provider county.
• Risk for being more than 50 miles from a
provider is associated with living in a
– small metropolitan areas & rural areas
– Mountain or WNC regions
– county with fewer children
Discussion, cont.
• Distance to care & population increments
needed to attract a PSS vary considerable
across PSS.
– Disease prevalence
– Type of specialty (procedural or cognitive)
– When certification became available / size of
the PSS
– Overlap with IM subspecialties
Limitations
• Some of the addresses may be home
addresses, potentially biasing estimates.
• Analysis assumes that a provider is
involved in patient care.
• In urban areas, straight-line distance
underestimates the travel time needed to
reach providers.
Future Research
• Repeat distance analysis using zip code
level data
• More detailed studies needed to assess the
adequacy of supply in areas that have
providers:
– Account for patient demand
– Wait time for appointments
– Estimates of provider-population ratios that
adjust for provider availability for patient care
• Qualitative studies of how children in areas
distant from PSS receive care.