Atlas: Social and Environmental Determinants of Health in Washington D.C.

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Introduction

An individual’s health outcomes are a result of a messy, complicated equation of conditions and events. To a geographer, that equation might look something like:
Environmental factors + Social Factors + Behaviors + Entropy = Health Outcomes
While we can’t predict the seemingly random results of entropy within the human body, many researchers have tried to solve for the other variables. In doing this, we can make informed assumptions about the health of populations and the individuals within them.

While we can easily observe vast differences in health outcomes between distant points across the globe, there are often also significant disparities at small scales. This atlas examines how a multitude of social and environmental factors impact health outcomes at a citywide scale. For this atlas, I have chosen to study Washington, D.C. because it demonstrates a stark geographic divide in health outcomes.

Map Concepts

Environmental determinants of health are the elements of one’s daily environment that might facilitate healthy living or detract from their health. These elements include air quality, sanitation, exposure to hazardous substances, and more. To map environmental factors in Washington D.C. I used the United States Department of Housing and Urban Development’s (HUD) 2015 Environmental Health Index.

Social determinants of health are the cultural, political, and socioeconomic circumstances an individual lives in that impact their health. Research suggests that the strongest social determinants of health measurable are almost solely a number of socioeconomic factors (Braveman, 2014). Most prominent among them, income, education, and employment. Other research suggests that race is a considerable factor, as people of color often experience racism and discrimination in healthcare and healthcare access (Yepez, 2019). These factors pose significant barriers to timely and high-quality healthcare treatment, and may, in combination with other factors, be effective proxy variables for nutrition, drug use, childhood development, mental health, and sleep (Braveman 2014).

For a concrete measure of healthcare accessibility, I chose to use scores from the 2022 Index of Medical Underservice (IMU) created by the Human Resources and Services Administration. The IMU assigns a score between 0 and 100 based on the combination of four variables: primary care physicians per 1,000 population, infant mortality rate, % population below the poverty level, and % population ages 65+. Underserved areas earn lower scores, and any tract earning a score of 62.0 or below qualifies as a Medically Underserved Area (MUA). In Washington D.C., every tract for which there is data qualifies as a MUA.

To map health outcomes, I created another index that combines disease rates for coronary heart disease, chronic obstructive pulmonary disease, chronic kidney disease, diabetes, and asthma. The resulting measure displays the relative likelihood of an individual experiencing one of such chronic diseases based on census tract. This measure is useful to compare to social and environmental determinants of health. Together, the maps show how impactful these determinants can be.

Because health can’t merely be defined as the absence of illness, I decided to use another measure of health. An American Community Survey Public Use Microdata Sample in 2018 had adults self assess their health, the options being poor, fair, good, very good, or excellent. Based on the sample, estimates were created for each category and tract. I chose to use the estimated percent of adults reporting very good or excellent health in the past 30 days. This method of self-assessment is valuable, as it allows us to see how people perceive their own health at a given moment.

In combination, these maps show how social and environmental inequities can manifest themselves into population health. The maps reveal a significant spatial correlation between determinants and outcome; there is a nearly uniform pattern across all five maps that shows the southeast side of the city as a hotspot for poor health determinants and outcomes. Those living towards the northwest side consistently have more advantageous determinants and health outcomes.

Maps

The HUD’s 2015 Environmental Health Index assesses neighborhood-level exposure to harmful toxins. Values are inverted and ranked by national percentile. A higher index score indicates that a tract experiences less exposure to environmental hazards, suggesting that the area produces better health outcomes. The HUD used data from the 2005 National Air Toxics Assessment.

This map shows an index of the strongest social determinants of health, and how they are experienced by different tracts in Washington D.C. The metrics I included were employment rate, household income, % with Bachelor’s degree or higher, and % population non-white. To standardize the metrics I converted them into Z-scores, combining the four scores together to create a collective index score for each tract. The results show a spatial divide through the center of the city. The southeastern tracts tend to have lower index scores, meaning they’re more disadvantaged. The opposite is true of most tracts towards the northwest.

The most Medically Underserved tracts overlap those that are inhabited by socioeconomically disadvantaged populations. This measure reiterates the trend apparent in the other maps; the southeast tracts of D.C. are at a greater disadvantage.

This map shows the likelihood of developing a chronic health condition for individuals in each tract. The map mirrors the pattern that emerged from mapping environmental and social determinants of health. This suggests that the relationship between determinant and outcome is significant.

This map shows a different measure of health than the prevalence rate of chronic disease. It reveals that positive self-assessments of health are more likely to come from tracts towards the northwest. It suggests that health determinants do not only dictate the likelihood of developing illnesses; social and environmental factors affect people’s experience of health in their bodies every day.

Note: Multiple mapping technologies were used in the creation of this project, but all layouts were created with ArcGIS Pro. I used R to clean and analyze datasets, and publish the atlas, but felt that the final product would not be cohesive if the maps were displayed on different platforms.

Citations

Braveman, Paula, and Laura Gottlieb. “The social determinants of health: it’s time to consider the causes of the causes.” Public health reports (Washington, D.C. : 1974) vol. 129 Suppl 2,Suppl 2 (2014): 19-31. doi:10.1177/00333549141291S206

Yepez, Laura. “The Shared Determinants of Health and Wealth.” Prosperity Now, 29 July 2019, prosperitynow.org/blog/shared-determinants-health-and-wealth.