Study: Zip Codes Play a Role in COVID-19 Severity

The importance of economic and social inequalities played a large role in how early individuals decided to seek access to health care, and what ZIP codes they lived in played a large role, results of a study published in the Annales of Internal Medicine showed.

But those differences disappeared by the time they left the hospital, either alive or dead, investigators from the University of Michigan and the University of Colorado said in a statement.

Even after adjusting for underlying health issues, investigators found that the social vulnerability index (SVI) of patients’ ZIP codes still made a difference.

The SVI is based on multiple factors to create a score based on an area’s average income, education level, and household density to the percentage of households led by single parents or where English was not the primary language.

The SVI has already been used in Michigan, as well as other states, to prioritize COVID-19 vaccination outreach.

These findings could potentially help policymakers identify less-privileged areas and provide more services to prevent and respond to COVID-19 cases, investigators said.

Furthermore, the study results also showed the role of hospitals in equalizing outcomes for individuals from unequal backgrounds.

Investigators used data from more than 2300 individuals who were hospitalized for COVID-19 in 38 hospitals across Michigan between March 2020 and December 2020.

The findings suggested that individuals who lived in the most underprivileged ZIP codes were more likely to have severe symptoms, including low blood oxygen levels, when admitted to the hospital.

Additionally, these individuals were more likely to need support for lung failure and other organs through technology such as ventilators once they were hospitalized.

However, the patients were not more likely to die than those who were from more-privileged areas and were no less likely to go back to their own homes instead of a nursing home.

“Once they’re getting that care, there are equal outcomes, which is encouraging,” Renuka Tipirneni, MD an assistant professor of internal medicine at Michigan Medicine, said in the statement. “This analysis zooms in on individual patients and zooms out on what’s influencing their outcomes in their neighborhood.”

The investigators used data from a statewide database called Mi-COVID19, which was funded by Blue Cross Blue Shield of Michigan through its Collaborative Quality Initiative efforts. The database pools anonymous data for individuals hospitalized with COVID-19.

Previous studies from the same investigators showed that the SVI at the county level influenced the COVID-19 case and death rates, but the new analysis suggests that the ZIP code-level SVI is more accurate.

More disadvantaged areas, or those with higher SVIs, were found across the state and nation and varied from rural areas to centers of cities. The numbers of the SVI ranges from 0 (low social vulnerability) to 1 (highest social vulnerability).

Investigators also divided the SVI into 4 quartiles and looked at the difference in the percentage of individuals who experienced each type of severe symptom, treatment option, and outcome by quartile. Additionally, the differences of several percentage points were seen in most measures and even factoring out underlying health conditions.

The study results highlight the importance of making information available to individuals about how and when they should seek care for worsening COVID-19 symptoms, investigators said.

Furthermore, the availability of information in multiple languages and ensuring that outpatient transportation to appointments and treatment are available when patients need the could make a huge difference, investigator said.

They also found that high SVIs have correlate with low COVID-19 vaccination rates, which investigators plan on examining when 2021 data become available on Mi-COVID19.

Reference

ZIP codes matter when it comes to severe COVID-19. EurekAlert. News release. February 21, 2022. Accessed February 22, 2022. https://www.eurekalert.org/news-releases/943909