Characterizing chronological accumulation of comorbidities in healthy veterans: a computational approach.


Understanding patient accumulation of comorbidities can facilitate healthcare strategy and personalized preventative care. We applied a directed network graph to electronic health record (EHR) data and characterized comorbidities in a cohort of healthy veterans undergoing screening colonoscopy. The Veterans Affairs Cooperative Studies Program #380 was a prospective longitudinal study of screening and surveillance colonoscopy. We identified initial instances of three-digit ICD-9 diagnoses for participants with at least 5 years of linked EHR history (October 1999 to December 2015). For diagnoses affecting at least 10% of patients, we calculated pairwise chronological relative risk (RR). iGraph was used to produce directed graphs of comorbidities with RR > 1, as well as summary statistics, key diseases, and communities. A directed graph based on 2210 patients visualized longitudinal development of comorbidities. Top hub (preceding) diseases included ischemic heart disease, inflammatory and toxic neuropathy, and diabetes. Top authority (subsequent) diagnoses were acute kidney failure and hypertensive chronic kidney failure. Four communities of correlated comorbidities were identified. Close analysis of top hub and authority diagnoses demonstrated known relationships, correlated sequelae, and novel hypotheses. Directed network graphs portray chronologic comorbidity relationships. We identified relationships between comorbid diagnoses in this aging veteran cohort. This may direct healthcare prioritization and personalized care.






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Publication Info

Hong, Julian C, Elizabeth R Hauser, Thomas S Redding, Kellie J Sims, Ziad F Gellad, Meghan C O'Leary, Terry Hyslop, Ashton N Madison, et al. (2021). Characterizing chronological accumulation of comorbidities in healthy veterans: a computational approach. Scientific reports, 11(1). p. 8104. 10.1038/s41598-021-85546-2 Retrieved from

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Elizabeth Rebecca Hauser

Professor of Biostatistics & Bioinformatics

The incorporation of personalized medicine to all areas of human health represents a turning point for human genetics studies, a point at which the discoveries made have real implications for clinical medicine.  It is important for students to gain experience in how human genetics studies are conducted and how results of those studies may be used.  As a statistical geneticist and biostatistician my research interests are focused on developing and applying statistical methods to search for genes causing common human diseases.  My research programs combine development and application of statistical methods for genetic studies, with a particular emphasis on understanding the joint effects of genes and environment. 

These studies I work on cover diverse areas in biomedicine but are always collaborative, with the goal of bringing robust data science and statistical methods to the project.  Collaborative studies include genetic and ‘omics studies of cardiovascular disease, health effects of air pollution, genetic analysis of adherence to an exercise program, genetic analysis in evaluating colon cancer risk, genetic analysis of suicide, and systems biology analysis of Gulf War Illness.

Keywords: human genetics, genetic association, gene mapping, genetic epidemiology, statistical genetics, biostatistics, cardiovascular disease, computational biology, diabetes, aging, colon cancer, colon polyps, kidney disease, Gulf War Illness, exercise behavior, suicide


Ziad F. Gellad

Professor of Medicine

Dr. Gellad is an associate professor of medicine in the Division of Gastroenterology at Duke University Medical Center and the Chief of Gastroenterology at the Durham VA Health Care System.  His research focuses on quality of care in gastroenterology, with a particular focus on colorectal cancer screening. Dr. Gellad has also received several innovation grants to develop and implement novel information technology platforms to improve the patient and clinician experience.  He is also an active contributor to the innovation and entrepreneurship activities within Duke University and co-founder of a health technology startup in Durham, NC.

Dr. Gellad received his MD and MPH degrees from Johns Hopkins University.  He completed a residency in internal medicine and a fellowship in gastroenterology at Duke University Medical Center.   Dr. Gellad is past-chair of the Quality Measures Committee of the American Gastroenterological Association, associate editor for GI & Hepatology News and is on the Board of Editors for Clinical Gastroenterology and Hepatology.


Christina D Williams

Adjunct Associate Professor in the Department of Medicine

Brian Sullivan

Assistant Professor of Medicine

I am a Physician Scientist in Gastroenterology, with a research focus in optimizing colorectal cancer (CRC) screening and surveillance recommendations. This includes evaluating current and evolving CRC screening strategies and identifying people at high risk for underlying hereditary/genetic CRC syndromes. 

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