Article Text

Download PDFPDF
Social inequality and the syndemic of chronic disease and COVID-19: county-level analysis in the USA
  1. Nazrul Islam1,2,
  2. Ben Lacey1,
  3. Sharmin Shabnam3,
  4. A Mesut Erzurumluoglu2,
  5. Hajira Dambha-Miller2,4,
  6. Gerardo Chowell5,
  7. Ichiro Kawachi6,
  8. Michael Marmot7
  1. 1 Nuffield Department of Population Health, University of Oxford, Oxford, Oxfordshire, UK
  2. 2 MRC Epidemiology Unit, University of Cambridge, Cambridge, UK
  3. 3 Leicester Diabetes Centre, University of Leicester, Leicester, UK
  4. 4 Department of Primary Care and Population Health, University of Southampton, Southampton, UK
  5. 5 Department of Population Health Sciences, Georgia State University, Atlanta, Georgia, USA
  6. 6 Department of Social and Behavioral Sciences, Harvard University T H Chan School of Public Health, Boston, Massachusetts, USA
  7. 7 UCL Institute of Health Equity, University College London, London, UK
  1. Correspondence to Dr Nazrul Islam, Nuffield Department of Population Health, University of Oxford, Oxford, Oxfordshire, UK; nazrul.islam{at}


Background Given the effect of chronic diseases on risk of severe COVID-19 infection, the present pandemic may have a particularly profound impact on socially disadvantaged counties.

Methods Counties in the USA were categorised into five groups by level of social vulnerability, using the Social Vulnerability Index (a widely used measure of social disadvantage) developed by the US Centers for Disease Control and Prevention. The incidence and mortality from COVID-19, and the prevalence of major chronic conditions were calculated relative to the least vulnerable quintile using Poisson regression models.

Results Among 3141 counties, there were 5 010 496 cases and 161 058 deaths from COVID-19 by 10 August 2020. Relative to the least vulnerable quintile, counties in the most vulnerable quintile had twice the rates of COVID-19 cases and deaths (rate ratios 2.11 (95% CI 1.97 to 2.26) and 2.42 (95% CI 2.22 to 2.64), respectively). Similarly, the prevalence of major chronic conditions was 24%–41% higher in the most vulnerable counties. Geographical clustering of counties with high COVID-19 mortality, high chronic disease prevalence and high social vulnerability was found, especially in southern USA.

Conclusion Some counties are experiencing a confluence of epidemics from COVID-19 and chronic diseases in the context of social disadvantage. Such counties are likely to require enhanced public health and social support.

  • access to hlth care
  • health inequalities
  • social inequalities
  • epidemics
  • epidemiology of chronic diseases

Data availability statement

All the data used in this study are publicly available and properly cited. Please contact for more information.

This article is made freely available for use in accordance with BMJ’s website terms and conditions for the duration of the covid-19 pandemic or until otherwise determined by BMJ. You may use, download and print the article for any lawful, non-commercial purpose (including text and data mining) provided that all copyright notices and trade marks are retained.

Statistics from

Request Permissions

If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.

Data availability statement

All the data used in this study are publicly available and properly cited. Please contact for more information.

View Full Text


  • NI and BL are joint first authors.

  • IK and MM are joint senior authors.

  • Twitter @HDambhaMiller

  • Contributors NI and BL conceptualised the study with the input from IK, MM, SS, AME, HD-M and GC. IK and MM were the cosenior authors. NI did the statistical analysis. NI and BL wrote the first draft of the manuscript. All authors contributed to data interpretations, and critical revisions of the manuscript. NI and BL are the guarantors.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Disclaimer Sponsors had no role in the design, analysis, or dissemination of the study. The views expressed in this article are those of the authors and not necessarily those of the entities the authors are affiliated with and/or supported by.

  • Map disclaimer The depiction of boundaries on this map does not imply the expression of any opinion whatsoever on the part of BMJ (or any member of its group) concerning the legal status of any country, territory, jurisdiction or area or of its authorities. This map is provided without any warranty of any kind, either express or implied.

  • Competing interests None declared.

  • Patient and public involvement statement Patient and public involvement was not applicable since this study did not involve patients and public directly. However, our findings will be appropriately disseminated to the public through personal and social communication tools.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.