From The New England Journal of Medicine
Some Journal readers may wonder what social epidemiology is. Berkman and Kawachi define it as "the branch of epidemiology that studies the social distribution and social determinants of health." The field incorporates the concepts and methods of "disciplines ranging from sociology, psychology, political science, economics, demography and biology." However, more is at stake than broadening the scope of inquiry beyond the usual physical and biologic suspects. At its best (as exemplified repeatedly in this book), social epidemiology embodies a new focus on the community as an entity in itself, an entity more complex than the sum of the individual persons who make it up, but one that acts on and through those people to influence the health status of each. This approach represents a conceptual shift in epidemiologic research and theory. It highlights features of the social world to which biomedical studies are ordinarily blind.
Physicians have known for a long time that the way people live affects their health. Indeed, the author or authors of the Hippocratic treatise Airs, Waters, Places enjoined "whoever wishes to pursue properly the science of medicine" to consider among other features of the place of practice the "mode of life of the inhabitants... whether they are heavy drinkers, taking lunch and inactive, or athletic, industrious, eating much and drinking little." More than two millennia were to pass before these and other intuitive hypotheses (most of which proved to be wrong) were put to the test. It is not news that poverty is associated with poor health, although controversy persists about the direction of causality (from poverty to illness or illness to poverty), about the most effective interventions (social measures or health measures), and about other such matters (which are discussed by Lynch and Kaplan in chapter 2).
It may not be news that people without means have less access to care and that the care they get is of lower quality. But it became news in recent years, and painful news at that, to learn that members of minority groups and women are less likely to receive aggressive medical and surgical interventions even when payment is not an issue (as in the case of patients who are covered by Medicare or enrolled in the Veterans Affairs system). The effect of discrimination on health is thoughtfully examined by Nancy Krieger, who begins chapter 3 with two statements: "Inequality hurts. Discrimination harms health." She then marshals the evidence to document both claims.
But it will be news to most physicians that higher mortality rates are associated with greater social disparity; in other words, the magnitude of the economic differential between the folks at the top and the folks at the bottom of the social ladder influences death rates. For example, in a study of income inequality and mortality in 300 U.S. metropolitan areas, areas with greater inequality between the groups had higher mortality rates than areas with narrower extremes. This is not another of the statistically significant but clinically unimportant findings sometimes reported by large population surveys. The aggregate excess in mortality was as great as the combined loss of life from lung cancer, diabetes, motor vehicle crashes, human immunodeficiency virus infection, homicide, and suicide. What is it about inequality? The short answer is that no one knows. Differences in identified individual risk factors account for less than half the observed disparity. Hypotheses about this phenomenon and ways to test them are incisively presented by Kawachi, Brunner, and Marmot in separate chapters.
Lisa Berkman, senior editor and coauthor of three chapters, is one of the pioneering researchers in social epidemiology. Her first major study, published 20 years ago, is a landmark. In longitudinal research on a randomly sampled population of the community, she identified persons in the top quartile of social connectedness (defined in terms of marital ties, kinship, friendships, and group participation) and found that they were less likely to die during the subsequent nine-year period than the relatively socially isolated persons in the lowest quartile. The statistical significance of the mortality differential held up after adjustment for health status and the risky health behavior recorded at the initial examination. She went on to show that lack of social support decreases the likelihood of survival after myocardial infarction, increases the probability of depression in the elderly, and leads to higher rates of cognitive decline. As an original investigator and careful scholar, she offers an integrated account of the effect on health of cultural, ethnic, and class-related variations in the structure and function of social networks.
The list of authors is a Who's Who of social epidemiology. Each chapter is thorough without being encyclopedic; the bibliographies are comprehensive without being exhaustive. This book gives physicians an intellectual adventure by putting new ways of looking at health problems in context. In addition to such notions as income disparity as a risk factor and social connectedness as a protective factor, Kawachi and Berkman provide a stimulating account of "social capital," a concept that has recently gained prominence and one that they define as "those features of social structures, such as levels of interpersonal trust and norms of reciprocity and mutual aid, which act as resources for individuals and facilitate collective action."
Social capital has a substantial effect on the probabilities of good or bad health. The epidemiologic research carried out by Kawachi and his coworkers has demonstrated significant correlations between health and such indicators of social capital as interpersonal trust, reciprocity, and the extent of membership in voluntary organizations. How might this come about? The possibilities include the placing of social constraints on deviant health behavior (smoking, drinking, and drug abuse), the availability of better community services and amenities as a result of political solidarity, and the provision of emotional support and respect. What maintains social capital? "Trusting social environments...be get trustworthy citizens." Can we design policy to build social capital? Finding ways to do so may be the most important task American democracy faces. This and related issues are addressed in Jody Heymann's splendid chapter on health and social policy.
What do I see for the coming editions? Permit me to be a visionary. These days, just about every physician encounters the word "genomics" and knows that large-scale DNA sequencing is expected to provide the precise structure of the human genome before 2003. Most know that genes specify proteins. However, the three-dimensional structure and function of the proteins cannot be determined from the DNA matrix. Some physicians are beginning to encounter the term "proteomics" -- the large-scale analysis of proteins that will become the scientific frontier of the post-genomic decade. These developments portend exciting times for medicine.
The coming scientific frontier will be some version of "sociobiomics" (a neologism that I hope will not outlive this book review). It will be a long-term, interdisciplinary research project to specify the forces within and among social groups that interact with the biologic uniqueness of each member of those groups (and the environment they inhabit) to determine whether individuals stay well or fall ill. Admittedly, my rhetoric is somewhat overheated, but it is meant to call attention to the context that Social Epidemiology illuminates and that future editions will shine an even brighter light on.
Leon Eisenberg, M.D.
Copyright © 2000 Massachusetts Medical Society. All rights reserved. The New England Journal of Medicine is a registered trademark of the MMS.
"As an academic psychiatrist-epidemiologists, I have long recognized the importance of psychosocial factors in the onset and course of psychiatric illness and in the response to therapeutic interventions. With medicine becoming more population-based and less individual-oriented, future practitioners must be schooled in the social conditions and behavioral risk factors relevant to disease and its prevention. In providing a resource that explicates the social determinants of illness and helps the reader to understand the impact of social organization and structure of health and access to healthcare, the editors make this book a valuable contribution to the literature on psychosocial epidemiology.*****" --Doody's
"This is an important book,...outstanding...The volume exhibits three particular strengths for epidemiology students and researchers. In the majority of the chapters, the authors began with presentations of theoretical concepts. A second strength of the volume is the recurring discussion of possible mechanisms that can explain the connections between social factors and health behaviours, disease risk and mortality. Finally the volume discusses the application of social epidemiology research to the design of effective public health interventions and social policies...a critical and timely addition to the field." -- Irene H. Yen, The Epidemiology Monitor, Aug/Sept 2000
"The sixteen chapters collected in this volume provide a powerful illustration of the interdisciplinary nature of social epidemiology. The individual chapters give significant attention to the historical work in the field. Many of the contributing authors are among the leading international scholars in the field of social epidemiology. This collection demonstrates the imperative for epidemiology to form interdisciplinary unions with other human and life science disciplines in order to advance understand of population health." -- Cam Mustard, Assoc Prof Public Health Science, Chronic Diseases in Canada, Vol 21, No. 3, 2000
"...provocative and stimulating...This book is a great resource because most of the chapters offer clear and helpful reviews which bring the reader up-to-date with theoretical and empirical developments in the field, ask interesting questions or attempt to clarify conceptual confusions."--International Journal of Epidemiology
"Berkman and Kawachi's book is brilliant."--Journal of Public Health MedicineVol.23, No.3 2001
"The volume exhibits three particular strengths for epidemiology students and researchers. In the majority of the chapters, the authors began with presentations of theoretical concepts.... A second strength of the volume is the recurring discussion of possible mechanisms that can explain the connections between social factors and health behaviors, disease risk and mortality.... Finally, the volume discusses the applications of the social epidemiology research to the design of effective public health interventions and social policies..... Social Epidemiology is a critical and timely addition to the field." --The Epidemiology Monitor