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

• 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

Access to Pediatric Subspecialty Care

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 straight-

line 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 Mean 75%ile 95%ileNeonatal Perinatal Medicine 3588 13 20 59Cardiology 1503 19 29 83Hematology Oncology 1553 24 30 90Critical Care Medicine 1013 24 35 92Endocrinology 889 24 37 95Pulmonology 627 28 39 106Infectious Diseases 838 29 38 102Allergy Immunology 514 29 36 106Gastroenterology 712 30 39 106Emergency Medicine 1075 33 45 123Nephrology 530 34 46 142Adolescent Medicine 396 40 54 140Developmental Behavioral Pediatrics 296 42 60 145Rheumatology 173 58 75 221Neurodevelopmental Pediatrics 185 71 85 208Sports Medicine 82 77 101 240

Population Weighted Distance to Care, in Miles

Table 2: Percent of Under 18 Population Living within Selected Distance by PSS, US Counties

Within 50 Miles of a

Provider100 or More Miles from

a ProviderNeonatal and Perinatal Medicine 92.9% 1.5%Pediatric Cardiology 87.5% 3.1%Pediatric Hematology/Oncology 85.8% 3.9%Critical Care Medicine 83.8% 4.1%Pediatric Allergy 83.6% 5.6%Pediatric Endocrinology 82.1% 4.4%Pediatric Infectious Disease 81.5% 5.2%Pediatric Pulmonology 81.4% 5.7%Pediatric Gastroenterology 81.3% 5.9%Pediatric Emergency Medicine 77.2% 8.1%Pediatric Nephrology 76.6% 8.8%Adolescent Medicine 73.1% 10.2%Development Behavioral Pediatrics 70.9% 11.5%Pediatric Rheumatology 64.6% 18.1%Neurodevelopmental Disabilities 58.5% 20.6%Pediatric Sports Medicine 53.0% 25.2%

Percent of Under 18 Population

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

Pediatric Subspecialty% with a Provider Mean Std. Dev.

COV%

Adolescent Medicine 33 0.43 1.18 277Critical Care Medicine 48 1.52 5.07 333Developmental Behavioral Pediatrics 32 0.45 1.38 307Neurodevelopmental Disabilities 21 0.19 0.55 287Neonatal Perinatal Medicine** 76 10.57 24.40 231Allergy 51 1.00 2.64 265Cardiology 60 2.16 4.59 212Endocrinology 48 1.35 6.76 501Infectious Diseases 44 1.10 4.47 407Pulmonology 43 1.03 4.26 413Emergency Medicine 40 1.08 3.13 290Gastroenterology 46 0.91 2.02 223Hematology Oncology 53 1.91 4.71 246Nephrology 35 0.68 1.88 275Rheumatology 23 0.22 0.69 315Sports 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

Provider : Under-18 Population (in 100,000)

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

0 100,000 200,000 300,000 400,000 500,000 600,000 700,000 800,000

Pediatric Cardiology

Pediatric Hematology Oncology

Pediatric Allergy

Critical Care Medicine

Pediatric Endocrinology

Pediatric Gastroenterology

Pediatric Infectious Diseases

Pediatric Pulmonology

Pediatric Emergency Medicine

Pediatric Nephrology

Adolescent Medicine

Developmental Behavioral Pediatrics

Pediatric Rheumatology

Neurodevelopmental Disabilities

Pediatric Sports Medicine

Ped

iatr

ic S

ub

spec

ialty

Predicted Pediatric Population Threshold

95% Confidence Interval

Figure 2: Population Increments Needed to Support Additional Providers in an MSA,

Non-procedural Subspecialties

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

1 2 3 4 5

Provider

Po

p'n

< 1

8

NeurodevelopmentalDisabilitiesRheumatology

Allergy Immunology

Dev't Behavioral

Infectious Diseases

Adolescent Medicine

Endocrinology

Hematology Oncology

Figure 3: Population Increments Needed to Support Additional Providers in an MSA,

Procedural & Intensivist Subspecialties

0

100,000

200,000

300,000

400,000

500,000

600,000

700,000

1 2 3 4 5

Providers

Po

p'n

< 1

8 Pulmonology

Gastroenterology

Critical Care Medicine

Emergency Medicine

Cardiology

Figure 4: Population Increments Needed to Support Additional Providers in an MSA,

Procedural & Intensivist Subspecialties

0

50,000

100,000

150,000

200,000

1 2 3 4 5

Providers

Po

p'n

< 1

8

Pulmonology

Gastroenterology

Critical Care Medicine

Emergency Medicine

Cardiology

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.