Using GIS to Analyze Inequality in Access to Dental Care in the District of Columbia

Abstract

Background:

Access to dental care in mixed-race and predominantly African American wards in the District of Columbia (DC) was investigated in relation to community development.

Methods:

This study used high-resolution geographic information system (GIS) tools to map all general dentistry and periodontal practice locations in DC wards. The spatial analysis contextualized each ward’s land use and demographic data obtained from DC government reports.

Findings:

The analysis revealed inter-ward inequity in dental care access, which was measured by proximity to and number of dental clinics in each DC ward. Residents in affluent wards had access to many dental practices and superior amenities. Residents in wards poorly served by public transportation and with few resources had few, if any, dental clinics.

Conclusions:

Dental practices are inequitably distributed across DC wards. DC policy should prioritize community development—specifically, resource allocation and community outreach—to promote health equity and improve access to and quality of dental care among residents of color.

Background

The 2000 Surgeon General report on oral health underscored that “there are profound and consequential disparities in oral health” that primarily affect persons who are poor and have racially and ethnically minoritized identities.¹ Sources of inequity include social determinants (eg, lack of financial resources, transportation, understanding of oral health’s roles in overall health). Persons with low incomes have compromised access to insurance coverage for dental services, and Medicaid offers limited dental coverage.^1,2 Dental care access inequity differs between and within states, exacerbated by shortages of dental professionals in identified areas.^3,4

Regional distributions of dental services have been evaluated using models based on a geographic information system (GIS) to determine the number of new dental practices needed to allow accessibility to a dentist within a certain number of miles.⁵ GIS has not, however, been used to study relationships between oral health care access and community development. Accordingly, this research contextualized each DC ward’s land use and demographic data, obtained from District of Colombia (DC) government reports, with spatial analysis enabled by GIS mapping of dental practice locations.

Methods

DC covers 68.34 miles of land⁶ and includes numerous historically African American communities. As defined by the DC Office of Planning, a ward is a district “established for administrative or political purposes” and represented by an elected council member.⁷ For each DC ward, we collected and summarized dental practice, land use, income, and employment status data. General dentistry and periodontal practice locations were collected online, entered into a database, and coded by specialty, street address, and zip code. Other data were obtained from DC government and census reports. We used the Quantum Geographic Information System to overlay the DC general and periodontal dental practice locations on a map of census tracts integrating population data to create a dental practice map and then overlaid ward boundaries on the map.

Results

Residents of DC’s Ward 4 have the most access to dental care, and residents of Ward 8 have the least. Residents of Wards 1, 5, and 7 also have compromised access to dental services. (See Figure.)

Figure.

Ward Map of Locations of DC General Dentistry and Periodontal Practices With Census Tract Population Data^a

^a Census tract-level demographic data from the 2018 American Community Survey were joined with US Census Bureau Tiger/Line shapefiles. Dental practice locations were obtained from a web-based dental directory database.⁸

Ward 4 is affluent, with a 2021 median income of $94 163 compared to the DC citywide median income of $91 414.⁹ It has low crime rates, abundant community organizations, neighborhood amenities (eg, retail), well-integrated Metrorail service, relatively high-performing public schools with strong parental support, and substantial unmet need for new affordable housing units.¹⁰ In 2021, about 31% of Ward 4 residents identified as White, a percentage slightly below the DC citywide average of 42%.⁹ When the wards were overlaid on the map of dental practice locations, it is apparent that there are numerous dental practices distributed throughout the ward. Taken together, the demographic data and map of dental practice locations suggest a relation between Ward 4’s community development and its residents’ access to oral health services.

Ward 8 communities are inhabited by residents with lower incomes and are less publicly resourced and economically developed. Although Ward 8 has been racially integrated since 1877,¹¹ it is now about 92% African American.¹² In 2021, the median household income in Ward 8 of $39 473 was the lowest in DC and less than half DC’s median income.¹² An influx of new residents to Ward 8 in the 1950s created economic and social disruption that continued into the 1990s. In 2000, 1 in 6 housing units in Ward 8 were vacant and 1 in 3 residents of Ward 8 lived in poverty.¹¹ The unemployment rate of 18% in Ward 8 is about 2.5 times higher than the average of 7.3% for the DC area.¹² When Ward 8 was overlaid on the map of dental practice locations, it’s clear that there is a lack of dental practices.

Data on median income and population density for all the wards are displayed in the Table.

Table.

Ward Statistics

Ward	Median Income	Square Miles	Population
Ward 1	$110 33913	2.514	91 67313
Ward 2	$112 24415	6.416	92 80915
Ward 3	$143 33917	10.418	84 97919
Ward 4	$94 1639	8.920	87 1509
Ward 5	$91 18921	10.222	90 38021
Ward 6	$113 92223	5.724	103 19723
Ward 7	$42 20125	8.426	80 66925
Ward 8	$39 47312	8.727	80 51712

Discussion

Residents of DC wards with high percentages of persons with minoritized racial and ethnic identities and low median incomes have more limited access to oral health services than residents of more affluent DC wards. They have less access to well-integrated public transportation and must travel farther to access dental care in DC than residents of wards that have more community development and investment. These findings align with data from similar studies of other regions of the United States. For example, a GIS study in Ohio also revealed lack of access to dental care among residents in historically rural and low-income areas.⁵

Conclusion

Inequitable distribution of dental practices across DC reveals inequity in dental care access. Some residents endure more obstacles to accessing dental services than others. Identifying neighborhoods with limited access should be a public policy priority to encourage reform and innovation (eg, student loan repayment options and other incentives for oral health clinicians to practice in culturally and economically diverse communities) and would help develop public health outreach programs that promote equitable access to quality oral health services.

Biographies

Jennita Davis is a student in the Rollins School of Public Health at Emory University in Atlanta, Georgia. She is a recent graduate of Howard University’s Interdisciplinary Studies Program with a concentration in bioethics. Her research interests include bioethics, health disparities, and reproductive rights.

Meirong Liu, PhD is an associate professor at the Howard University School of Social Work in Washington, DC. She has led evaluations of several federally funded programs that established multi-institutional, comprehensive, long-term partnerships to address oral health disparities and improve oral health disparity research in underserved populations. Her research focuses on program development, program evaluation, and the policies and programs that provide access to public benefits for vulnerable populations.

Dennis Kao, PhD is an associate professor at the Carleton University School of Social Work in Ottawa, Ontario, Canada. His research focuses on health equity, aging-friendly communities, geographic information systems, data visualization, and digital storytelling.

Xinbin Gu, MD, PhD is a professor and the associate dean of research at the Howard University College of Dentistry in Washington, DC. She is the principal investigator of the Howard University/Johns Hopkins University Summer Research Experience Program in Oral Health Disparity for Underrepresented Racial and Ethnic Students, which provides innovative training to students from underrepresented communities to conduct health disparity research and practice.

Gail Cherry-Peppers, DDS, MS is an associate professor and the director of community dentistry at the Howard University College of Dentistry in Washington, DC. Her research focuses on oral health disparities and their associations with chronic diseases.