His research interests include studies of mechanisms for the development of cardiovascular disease, with emphasis on understanding the role of the gut microbiome, inflammation and oxidant stress in the pathogenesis of atherosclerosis and other inflammatory diseases. A renowned physician scientist, Dr. Hazen has made pioneering discoveries in new understandings of mechanisms contributing to cardiovascular and inflammatory disease research. He is credited with numerous seminal discoveries linking gut microbial pathways to cardiovascular disease pathogenesis, as well as enumerating the role of myeloperoxidase and other inflammatory and oxidative pathways in cardiovascular disease. Dr. Hazen is among the top 0.1% cited researchers in the world with over 140,000 citations. He has published over 475 peer-reviewed articles in top tier basic and clinical journals alike in the fields of atherosclerosis, lipoprotein metabolism, gut microbiome, inflammation, vascular biology, and other topics related to preventive cardiovascular medicine. His research in multiple areas has impacted clinical practice, and lays the foundation for FDA- and EU-cleared diagnostic tests for cardiovascular disease risk assessment in use worldwide. He is listed as inventor on over 100 patents, and his research has helped to spawn pharmaceutical development of cardiovascular disease drugs in clinical trials.