The Center for the Biology of Chronic Disease

Home	About	Nobel	Donate
The Book	Meetings	Grants	Contact

Sean X. Leng, MD, PhD

Assistant Professor of Medicine, Division of Geriatric Medicine and Gerontology, Johns Hopkins University School of Medicine

REVIEW

I have read Dr. Polansky's book entitled Microcompetition with Foreign DNA and the Origin of Chronic Disease with great interest. His book has caught my attention because we currently do not have any good theory about the origin of chronic diseases, even though we think that we understand quite well, the biological basis or pathogenesis of some individual chronic medical conditions. Upon finishing my reading, I have found that this is an amazingly well-written book. In this book, Dr. Polansky has clearly presented the theory of "microcompetition with foreign DNA." To support this theory, Dr. Polansky has cited a tremendous amount of evidence, most of which is the most up-to-date throughout the book, and particularly, for several of the most common chronic diseases, such as atherosclerosis-related coronary artery disease and stroke, autoimmune disease, and osteoarthritis. Without going into great length of detail, as several reviewers have done that already, I strongly recommend this book to both clinicians and scientists who are interested in a better understanding of the origin of chronic disease.

This book is highly relevant to my work. I like the "microcompetition" part of the theory in particular. First, as a geriatrician (physician specialized in providing clinical care for older adults), I see older patients with multiple and complex chronic diseases all the time. Understanding the origin of chronic disease will certainly help me to treat, and better off to prevent, these chronic diseases for my patients. In addition to the theory of "microcompetition with foreign DNA" on the origin of chronic disease discussed in this book, here I describe, from a different angle, several levels of "microcompetition" in older patients. At the biological level, multiple chronic diseases and other stressors compete for limited physiologic reserve that older patients have, such as nutrition (including micronutrients) and immune defense mechanisms, leading to the development of other chronic conditions or the worsening of existing chronic conditions. From the patient's perspective, multiple chronic diseases and their crippling effects and associated costs compete for patients' already reduced functional level and financial resources, leading to further functional decline and disability, as well as to patients' inability to actively participate (both financially and physically) in prevention and treatment of chronic diseases. From the clinician's perspective, setting the treatment priority from multiple competing chronic conditions for the patients is one of the most challenging tasks that clinicians face everyday. Secondly, as a physician/scientist, my research interest is focused on frailty in older adults. Frail older adults, with multiple chronic conditions and further impaired physiologic reserve, are particularly vulnerable to adverse clinical outcomes from acute illnesses as well as chronic diseases. The "microcompetition with foreign DNA" theory provides a provocative, yet potential, hypothetical mechanism that may contribute to the development of frailty, an important chronic condition in older adults. Managing frailty and it's associated adverse clinical outcomes in older adults is indeed the heart and soul of geriatric medicine. As the population ages in this country and around the world, providing the best clinical care to frail older adults in a cost-effective manor is becoming the most pressing priority for the whole medical community.

BIOGRAPHY

Before he immigrated to the United States, Dr. Sean X. Leng obtained his MD at Jiangxi Medical College in Jiangxi Province and practiced in Allergy and Clinical Immunology at Peking Union Medical College Hospital in Beijing, the People’s Republic of China. He then obtained a PhD in Molecular Virology and Immunology at Texas A&M University followed by a two-year postdoctoral research fellowship in cytokine research at Yale University School of Medicine. Dr. Leng then came back to clinical training in Internal Medicine at St. Luke’s-Roosevelt Hospital Center, a Columbia University College of Physicians and Surgeons' training program in New York City followed by a two-year clinical and research fellowship in Geriatric Medicine and Gerontology at the Johns Hopkins University School of Medicine. Currently, Dr. Leng is an Assistant Professor of Medicine in the Division of Geriatric Medicine and Gerontology, Department of Medicine, the Johns Hopkins University School of Medicine. In addition to his clinical practice of geriatric medicine, his research at Hopkins has been focused on the frailty syndrome in older adults. Dr. Leng has had significant scientific findings on the role of inflammation, cytokines, and immune and endocrine dysregulations in the pathogenesis of frailty either published or in press in several prominent peer-reviewed journals in geriatric medicine and aging research, such as the Journal of the American Geriatric Society (JAGS 50:1268-1271, 2002), Journal of Gerontology Medical Sciences, Mechanisms of Aging and Development, and Aging Clinical and Experimental Research.

MORE REVIEWS