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Complex Systems and Population Health: A Primer
Yorghos Apostolopoulos, Kristen Hassmiller Lich, Michael Kenneth Lemke
Oxford University Press 2020


Very few books are truly revolutionary- but this might just be one of them. Released coincidentally, but perhaps tellingly, in the middle of the COVID-19 pandemic, the book proceeds to make the case for both the wisdom and necessity of applying complex systems thinking to any study of population health. As Sandro Galea, Professor of Public Health at Boston University, points out in his foreword, even a decade ago systems science and population health science were strangers, with the latter largely relying on reductionist analytic strategies to identify single causes and disease states. While this approach historically served medicine well in identifying, for example, the causative role of smoking in lung cancer, it has been much less useful in addressing the so-called “modern” health challenges such as obesity, mental health problems, and neurodevelopmental issues. In addition, it has done little to address stubbornly persistent health inequities in areas including infant mortality rates. What is needed now is a much deeper understanding of how some of the most intractable population health challenges of our time are embedded in, shaped by, and/or consist of complex systems, and a willingness to apply complex systems science approaches to solve them. This book is the first to response to that need.

Made up of five sections broadly addressing concepts, theory, research design, methodology and analytic techniques, the book aims to blend old, current and new thinking to move the population health field forward, and improve the health of all people as equitably and efficiently as possible. Chapter 3 by Scott Page and Jon Zelner is particularly strong, arguing that population health outcomes and disparities need to be understood as the products not of isolated complex systems, but as the end result of a complex adaptive system of systems (CASoS). Consequently, each system must be understood both in isolation and in terms of its interaction with other systems if we are to truly understand what is going on in producing the whole picture. Chapter 7 by Leah Frerichs and Natalie R. Smith addresses ways to design population health research so that it is grounded in this new complex systems science, while another particularly strong contribution by Michael Lemke in Chapter 8 introduces model thinking and formal modeling as a way to improve our mental models in population health research. In Chapter 12, Nathaniel Osgood makes the case for dynamic (simulation) models as a central tool in this “science of the whole”. These models express dynamic hypotheses about the underlying processes that are driving systems, and are particularly important for intervention science. They hold promise for understanding system vulnerabilities and leverage points, identifying areas where investments could secure the greatest improvements. Later chapters address agent-based modeling, hybrid simulation modeling, and microsiumulation models, and the tremendous potential they have to inform health policy.

At a time when we appear to be at a “tipping point” for solving the pressing health problems of our time this book provides a new perspective, along with new tools and techniques that together form a new paradigm that will allow us to “dig deeper,” expanding our understanding of the deep systemic drivers of modern health challenges. Despite its methodologic and analytic content this book is as advertised – a primer. It will be useful reading for academics wanting to incorporate systems science into their own work or into their student mentoring, for graduate students, public and population health and healthcare professionals from all disciplines, and policymakers. The book has few weaknesses, but it is text heavy with very few figures and diagrams. Greater attention to visual representations of modeling concepts and pictorial representations of system maps could add to the book’s appeal and might be useful for future editions. Regardless, this book is both welcome and timely, and is highly recommended for anyone with an interest in population health.

Shirley Ann Russ MD MPH

Consultant to LCIRN