Study explains large geographic health disparities in the U.S.

Reviewed by Emily Henderson, B.Sc.Oct 15 2020

Bottom line:

60% of American adults have a chronic condition, but adults in Mississippi are 50% more likely to have one than adults in Colorado. In Denver, rates of chronic conditions vary 3-fold across zip codes. What is the reason the United States has such large geographic health disparities?

One explanation is that people who live in Mississippi are different in many ways from people in Colorado, and those differences--such as economic status or demographics including age and gender--may cause the health disparity. Another possibility is that the place where a person lives actually affects their health.

A new study disentangles these explanations by examining millions of people who moved to new neighborhoods, counties, and states, and then traced how their health changed after the move.

The study found that a person's risk of an uncontrolled chronic condition increased after moving to a place where the uncontrolled chronic condition was more common. For example, moving from a 10th-ranked zip code to 90th-ranked zip code for a given chronic condition was associated with a significantly increased prevalence of uncontrolled blood pressure of 7 percentage points, uncontrolled diabetes of 1 percentage point, obesity of 2 percentage points, and depressive symptoms of 3 percentage points among movers.

Results:

The researchers found that a persons' place of residence substantially influences their risk of uncontrolled chronic disease. Place mattered the most to a patient's risk of high blood pressure and depression, and to a smaller extent, uncontrolled diabetes and obesity.

Why the Research Is Interesting: Unlike prior research, this study evaluated changes in health outcomes over time within the same individual before and after the person moved to a new environment. The findings could have important implications for the design of public policies that target the underlying sources of increasing health disparities in the United States.

Who: About 5 million adults treated at Veterans Health Administration (VHA) facilities in the United States, including 1 million adults who moved zip codes and 4 million adults who did not move.

When: Patients treated at all VHA facilities in the United States from 2008-2018.

What: The study examined how much a person's place of residence contributed to their health outcomes by comparing their risk from common chronic conditions before and after they moved.

How: Researchers studied electronic medical records of all patients treated at VHA facilities from 2008-2018 who moved at least once or did not move at all. They identified who moved based on their zip code of residence, and tracked movers' health outcomes including blood pressure, diabetes, symptoms of depression and obesity before and after the move.

Using statistical models that adjusted for the person's characteristics, the time since they moved, and national trends, the researchers evaluated how much a person's health outcome changed after moving to a new zip code where the health outcome was more (or less) common than in their origin zip code.

Study conclusions:

In this retrospective study of patients treated at VHA facilities, the researchers found that the place where a person lived substantially affected their likelihood of having poorly controlled blood pressure or experiencing symptoms of depression. They also found that where a person lived somewhat affected their likelihood of having poorly controlled diabetes or obesity.

Said Mount Sinai's Dr. Aaron Baum of the research: This study confirms something Americans are currently acutely aware of: where you live affects your health. By evaluating medical records of millions of adults before and after they moved to a new neighborhood, we showed that where a person moved to affected their risk of having a poorly controlled chronic condition.

In addition to individual behaviors like healthy eating and exercise, our findings suggest that local and regional factors substantially influence the health of the 60% of American adults who have a chronic condition.