Gordis Epidemiology

434 Pages·2019·24.56 MB·English

by  David D. Celentano

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2015v1.0
Gordis Epidemiology
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6th Edition
Gordis
Epidemiology
David D. Celentano, ScD, MHS
Dr. Charles Armstrong Chair and Professor
Department of Epidemiology
Johns Hopkins Bloomberg School of Public Health
Baltimore, Maryland
Moyses Szklo, MD, MPH, DrPH
University Distinguished Professor
Department of Epidemiology
Johns Hopkins Bloomberg School of Public Health
Baltimore, Maryland
1600 John F. Kennedy Blvd.
Ste 1600
Philadelphia, PA 19103-2899
GORDIS EPIDEMIOLOGY, SIXTH EDITION ISBN: 978-0-323-55229-5
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Cover credit:
An original watercolor “Remembering Baltimore” by
Haroutune K. Armenian, MD, DrPH
Professor Emeritus
Department of Epidemiology
Johns Hopkins Bloomberg School of Public Health
Printed in Canada
Last digit is the print number: 9 8 7 6 5 4 3 2 1
In Memoriam
LEON GORDIS, MD, MPH, DrPH
1934–2015
Preface
Epidemiology is one of the foundational disciplines of the previous edition. In the fifth edition, learning
underlying public health. Clinical research relies heavily objectives were inserted in most chapters, and we have
on epidemiologic methods and contemporary medical revised these and updated the examples throughout.
care research, particularly in comparative effectiveness Additional new review questions have been added to
studies and statistical approaches to “big data” (as in most chapters. A significant change has been to the
the use of the electronic medical record for health presentation and order of the methods in epidemiology
studies). As Dr. Leon Gordis wrote in his preface to that were previously presented at the end of Section I
the fifth edition, “Epidemiology is the basic science of and more extensively in Section II. Rather than leading
disease prevention and plays major roles in developing with the randomized trial (or the “experimental” design)
and evaluating public policy relating to health and to and then comparing observational study design to the
social and legal issues.” There are many uses of epi- gold standard, we have organized the presentation of
demiology today. The majority of epidemiologic research epidemiologic methods along a study continuum from
focuses on establishing etiologic associations between clinical observation, to case-series, to the use of ecologic
putative risks and health outcomes. However, epidemi- studies, and then to cross-sectional investigations as
ology is also widely used in the evaluation of primary the foundational approach to epidemiologic hypothesis
and secondary prevention programs, comparisons of development. We then follow with case-control and
interventions, and the evaluation of policy at the cohort designs, leading up to the randomized trial.
population level. Epidemiologic findings commonly This more organically follows the development, in
find their way into public media, providing the public our opinion, of how epidemiologic observations and
and policy makers with data to guide personal decisions hypotheses are developed in the daily practice of doing
regarding their behavior. Increasingly, the scrutiny epidemiology.
focused on epidemiology may cause researchers and As with the previous edition, the sixth edition
practitioners some discomfort, as the interpretation of consists of three sections. Section I addresses how
basic epidemiologic principles can be subject to con- epidemiology is used to understand health and the
siderable error. Our task is to make the thinking development of diseases in populations as well as the
underlying epidemiology transparent. basis for interventions to influence the natural history
This book is intended to be a basic introduction to of disease. The first six chapters provide the conceptual
the definitions, logic, and use of the epidemiologic framework underlying the discipline of epidemiology
method to elucidate factors influencing health and and present many of the basic principles of the disci-
disease. We have tried to illustrate the principles with pline. Chapter 1 provides an overview of epidemiology,
examples of how epidemiology is applied in the real using many historical examples to illustrate how the
world. The examples selected include both “classic field developed. Chapter 2 is concerned with how
examples” from the early days of the development of disease is transmitted in populations, both directly (in
the discipline of epidemiology to contemporary exam- the case of infectious pathogens) and indirectly (for
ples. Where appropriate, we draw on examples pertain- example, through a vector such as a mosquito or
ing to clinical practice. contaminated air). The basic terms used in epidemics
Upon the passing of Dr. Gordis in 2015, the sixth are presented and illustrated to guide the student in
edition of this book has been revised by two new seeing how these principles and terms are used. Chapter
authors, both of whom worked with and under Professor 3 addresses disease surveillance and how we measure
Gordis and have been actively engaged in teaching morbidity in populations, while Chapter 4 is concerned
epidemiology at Johns Hopkins for over four decades. with aspects of mortality and measures of disease impact
We have generally retained the structure and organization in populations. Chapter 5 focuses on ways to detect
vvii
Preface vii
disease in populations, comparing different approaches concept of risk is expanded to include the calculation
to differentiate people who have a disease from those and interpretation of the attributable risk, the population
who are disease free, articulating how screening tests attributable risks, and their use in evaluating the success
can be adjusted to better diagnose those with or those of prevention programs. Causal inference is introduced
without the disease in question. The issues of the in Chapter 14 and focuses on how to derive inferences
reliability and validity of screening tests are of critical in epidemiologic investigations. Chapter 15 presents
interest to both clinicians and to those planning for issues of bias, confounding, and interaction in epide-
health services. Finally, Chapter 6 presents how the miologic studies and discusses how they influence causal
natural history of disease can be used to best express inference. Finally, Chapter 16 addresses the role of
disease prognosis, using examples of case-fatality and genetic and environmental contributions to the etiology
survivorship. of disease, and presents new methods of genetic research
Section II details the methods used by epidemiolo- commonly used in epidemiologic studies today.
gists primarily to ascribe associations between a Section III addresses the uses of epidemiology in
hypothesized exposure (risk) and a health outcome. everyday public health. The final four chapters address
Chapter 7 discusses the initial observations made in some of the critical issues facing the field today. Chapter
clinical practice (the case report) leading to a recognition 17 illustrates how epidemiologic principles and designs
of an accumulation of cases that appear to have some described in Sections I and II are used in the evaluation
commonalities (the case series). This is followed by an of health services. Chapter 18 addresses the use of
introduction to the ecologic design and its analysis, epidemiology to evaluate screening programs, while
with cautions as to its interpretation. Finally, cross- Chapter 19 details how epidemiology can be used to
sectional (snapshot) studies are presented as the address major areas of public health policy. The final
groundwork for hypothesis development. Chapter 8 chapter summarizes ethical issues confronted in the
then provides an introduction to observational studies practice of epidemiology and reviews some of the
as commonly used in epidemiology, addressing case- important professional issues confronted by the field
control and cohort studies, which are then compared today.
in Chapter 9. To this point, we are addressing exposures We have continued in Professor Gordis’ use of
as they occur in populations, where we are observers illustrations and examples to demonstrate how epide-
of exposures and their putative impacts on health miologic issues and principles are put into practice.
outcomes. In Chapter 10 we then move to the “experi- We have updated examples extensively and added new
mental” approach (randomized trial) in which the examples throughout the text. Many of the prior
investigator “assigns” exposure or health interven- chapters have been extensively edited and updated,
tion—generally randomly—to study participants to with some chapters being greatly expanded. The genetic
address how this influences the health outcome. In epidemiology presentation has been heavily edited and
this case the exposure is under the control of the updated, reflecting the amazing growth in genomics
investigator, not the study participant, a crucial differ- research in the past 5 years. In Chapter 16 we have
ence in the randomized trial as compared to the cohort added a glossary of genetic epidemiology terms to
or other observational study design. Chapter 11 dis- provide the student with some guidance for this
cusses a series of issues involved in the conduct of somewhat complex field. Finally, new review questions
randomized trials, including sample size, power, and have been added at the end of most chapters.
generalizability; determining efficacy (vs. effectiveness); Our aim for this book is to allow the reader to
ethical considerations; and the US Federal Drug appreciate how epidemiology can be used to respond
Administration phases for evaluating new drugs. In to population health problems confronting society today.
Chapter 12 we present issues on estimating risk, includ- Our expectation is not that the reader will be able to
ing absolute and relative risk and their interpretation, conduct an epidemiologic investigation. Rather, we
calculating and interpreting an odds ratio in a case- hope that there will be an appreciation of what epi-
control study and in a cohort study, and doing so in demiology is, what the basic research and evaluation
a matched-pairs case-control study. In Chapter 13 the designs are, and how to interpret the basic findings in
viii Preface
an epidemiologic study. We hope that the excitement are quintessential Baltimore, much as the “Painted
we feel about the uses of epidemiology will come across Ladies” are identified with San Francisco. Much of Dr.
to the reader of this text. Gordis’ research centered on pediatric and childhood
The cover illustration selected for this edition of disease in Baltimore, as illustrated in many of the
Gordis Epidemiology has special meaning. This original examples in this text. We are particularly proud to
watercolor by Haroutune Armenian, MD, DrPH, created include this tribute by Dr. Armenian to Dr. Gordis and
in August 2017, is titled “Remembering Baltimore.” to our first revision of his world-renowned text. This
Professor Armenian was a professor of epidemiology, sixth edition has kept our mind on our friend and
deputy chair to Professor Gordis for many years, and mentor.
interim chair from 1993–94, until Jon Samet became
chair. “Remembering Baltimore” truly captures the urban David D. Celentano
landscape of Baltimore, Dr. Gordis’ adopted home for Moyses Szklo
some 60 years. The distinctive rowhomes on the harbor August 2018