Introduction to Epidemiology

Transcription

1 45175_FM_i_xx.qxd:Merrill 7/10/12 4:08 PM Page i Introduction to Epidemiology Sixth Edition Ray M. Merrill, PhD, MPH, MS Professor Department of Health Science Brigham Young University Provo, Utah

2 45175_FM_i_xx.qxd:Merrill 7/10/12 4:08 PM Page ii World Headquarters Jones & Bartlett Learning 5 Wall Street Burlington, MA info@jblearning.com Jones & Bartlett Learning books and products are available through most bookstores and online booksellers. To contact Jones & Bartlett Learning directly, call , fax , or visit our website, Substantial discounts on bulk quantities of Jones & Bartlett Learning publications are available to corporations, professional associations, and other qualified organizations. For details and specific discount information, contact the special sales department at Jones & Bartlett Learning via the above contact information or send an to specialsales@jblearning.com. Copyright 2013 by Jones & Bartlett Learning, LLC, an Ascend Learning Company All rights reserved. No part of the material protected by this copyright may be reproduced or utilized in any form, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without written permission from the copyright owner. Introduction to Epidemiology, Sixth Edition is an independent publication and has not been authorized, sponsored, or otherwise approved by the owners of the trademarks or service marks referenced in this product. Some images in this book feature models. These models do not necessarily endorse, represent, or participate in the activities represented in the images. This publication is designed to provide accurate and authoritative information in regard to the Subject Matter covered. It is sold with the understanding that the publisher is not engaged in rendering legal, accounting, or other professional service. If legal advice or other expert assistance is required, the service of a competent professional person should be sought. Production Credits Publisher: Michael Brown Managing Editor: Maro Gartside Editorial Assistant: Kayla Dos Santos Editorial Assistant: Chloe Falivene Associate Production Editor: Rebekah Linga Senior Marketing Manager: Sophie Fleck Teague Manufacturing and Inventory Control Supervisor: Amy Bacus Composition: Lapiz Online Cover Design: Michael O Donnell Cover Image: Yalik/ShutterStock, Inc. Printing and Binding: Edwards Brothers Malloy Cover Printing: Edwards Brothers Malloy To order this product, use ISBN: Library of Congress Cataloging-in-Publication Data Merrill, Ray M. Introduction to epidemiology. 6th ed. / Ray M. Merrill. p. ; cm. Includes bibliographical references and index. SBN (paper) -- ISBN (paper) I. Title. [DNLM: 1. Epidemiologic Methods. 2. Epidemiology. WA 950] dc Printed in the United States of America

3 45175_FM_i_xx.qxd:Merrill 7/10/12 4:08 PM Page iii Dedication To our son Andrew who keeps us smiling.

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5 45175_FM_i_xx.qxd:Merrill 7/10/12 4:08 PM Page v Table of Contents About the Author Preface New to the Sixth Edition Introduction xiii xv xvii xix CHAPTER 1 Foundations of Epidemiology 1 Objectives 1 Activities in Epidemiology 3 Role of Epidemiology in Public Health Practice 4 Epidemics, Endemics, and Pandemics 6 Case Concepts in Epidemiology 7 The Epidemiology Triangle 8 Some Disease Transmission Concepts 9 Modes of Disease Transmission 10 Chain of Infection 11 Other Models of Causation 12 Levels of Prevention 13 Conclusion 18 Exercises 18 Study Questions 18 References 20

6 45175_FM_i_xx.qxd:Merrill 7/10/12 4:08 PM Page vi vi Table of Contents CHAPTER 2 Historic Developments in Epidemiology 23 Objectives 23 Hippocrates, the First Epidemiologist 24 Disease Observations of Sydenham 25 The Epidemiology of Scurvy 26 Epidemiology of Cowpox and Smallpox 27 Epidemiology of Childbed Fever in a Lying-in Hospital 28 John Snow s Epidemiologic Investigations of Cholera 29 Epidemiologic Work of Pasteur and Koch 32 The Invention of the Microscope 33 John Graunt and Vital Statistics 34 Occupational Health and Industrial Hygiene 35 Florence Nightingale 36 Typhoid Mary 37 Vitamins and Nutritional Diseases 38 Beginning of Epidemiology in the United States 39 Historical Development of Morbidity in Epidemiology 41 The Epidemiology of Breast Cancer 43 The Framingham Heart Study 43 Cigarette Smoking and Cancer 44 Conclusion 44 Exercises 45 Study Questions 46 References 47 CHAPTER 3 Practical Disease Concepts in Epidemiology 49 Objectives 49 Communicable and Noncommunicable Diseases and Conditions 50 Natural History of Disease 51 Classifying Disease 53 Portals of Entry to the Human Body 56 Incubation Periods for Selected Infectious Diseases 57 Later Stages of Infection 59 Zoonoses 60 International Classification of Diseases 63 Notifiable Diseases in the United States 63 Protecting Public Health Through Immunization 66 Herd Immunity 68 Communicable Disease Prevention and Control 72 Environmental Control 72

7 45175_FM_i_xx.qxd:Merrill 7/10/12 4:08 PM Page vii Table of Contents vii Host-Related Control and Prevention 73 Infection Control and Prevention Measures 74 Changing Emphasis in Epidemiologic Studies 74 Nutritional Deficiency Diseases and Disorders 76 Chronic Diseases and Conditions 77 Prevention and Control 78 Disability 79 Healthy People Initiatives 81 Conclusion 84 Exercises 84 Study Questions 85 References 85 CHAPTER 4 Design Strategies and Statistical Methods in Descriptive Epidemiology 87 Objectives 87 Descriptive Study Designs 89 Types of Data 94 Ratios, Proportions, and Rates 94 Tables, Graphs, and Numerical Measures 103 Measures of Statistical Association 111 Conclusion 114 Exercises 114 Study Questions 115 References 117 CHAPTER 5 Descriptive Epidemiology According to Person, Place, and Time 119 Objectives 119 Person, Place, and Time 120 Person 120 Place 132 Time Trends 133 Evaluation 144 Public Health Surveillance 145 Causal Insights 149 Conclusion 151 Exercises 151 Study Questions 152 References 152

8 45175_FM_i_xx.qxd:Merrill 7/10/12 4:08 PM Page viii viii Table of Contents CHAPTER 6 General Health and Population Indicators 155 Objectives 155 Health Indicator 156 Birth 157 Mortality 159 Types of Mortality Rates 164 Infant Mortality 165 Maternal Mortality Rate 169 Proportional Mortality Ratio 171 Death-to-Case Ratio 171 Years of Potential Life Lost 172 Conclusion 174 Exercises 175 Study Questions 175 References 178 CHAPTER 7 Design Strategies and Statistical Methods in Analytic Epidemiology 179 Objectives 179 Observational Analytic Studies 180 Case-Control Study Design 180 Odds Ratio in Case-Control Studies 184 Bias in Case-Control Studies 185 Controlling for Bias in Case-Control Studies 187 Strengths and Weaknesses of Case-Control Studies 188 Case-Crossover Study Design 188 Nested Case-Control Study Design 190 Cohort Study Design 190 Risk Ratio in Cohort Studies 191 Rate Ratio in Cohort Studies 192 Double-Cohort Studies 195 Selecting the Study Cohort 195 Bias in Cohort Studies 196 Controlling for Bias in Cohort Studies 197 Strengths and Weaknesses of Cohort Studies 198 Effect Modification 198 Conclusion 199 Exercises 200

9 45175_FM_i_xx.qxd:Merrill 7/10/12 4:08 PM Page ix Table of Contents ix Study Questions 201 References 202 CHAPTER 8 Experimental Studies in Epidemiology 203 Objectives 203 Experimental Study Designs 204 Randomization 205 Blinding 205 Nonrandomization 206 Designing a Randomized Controlled Trial 207 Pilot Study 210 Selected Special Types of Randomized Study Designs 210 Strengths and Weaknesses of Double-Blind Randomized Clinical Trials 212 Ethics in Experimental Research 212 Conclusion 215 Exercises 217 Study Questions 217 References 219 CHAPTER 9 Causality 221 Objectives 221 Statistical Inference 222 Hypothesis Development and Testing 222 Causal Inference 228 Causal Criteria 230 Web of Causation 232 Decision Trees 236 Fish Bone Diagram (Cause-Effect Diagram) 239 Conclusion 240 Exercises 240 Study Questions 241 References 243 CHAPTER 10 Field Epidemiology 245 Objectives 245 Conducting a Field Investigation 246

10 45175_FM_i_xx.qxd:Merrill 7/10/12 4:08 PM Page x x Table of Contents Investigation of a Foodborne Illness 253 Basic Epidemiologic Questions 257 Disease Clusters 258 Conclusion 264 Exercises 265 Study Questions 265 References 267 CHAPTER 11 Chronic Disease Epidemiology 269 Objectives 269 Chronic Disease Epidemiology 270 The Environment and Chronic Health Problems 273 Behavior and Chronic Health Problems 281 Heredity and Chronic Health Problems 286 Multifactorial Etiology in Chronic Disease Epidemiology 287 Priorities in Disease Prevention and Control 289 Conclusion 289 Exercises 291 Study Questions 291 References 292 CHAPTER 12 Clinical Epidemiology 297 Objectives 297 Clinical Epidemiology 298 Screening and Diagnosis 298 Evaluating the Screening Test 300 Prognosis 303 Health Outcomes Research 307 Conclusion 307 Exercises 308 Study Questions 309 References 310 GLOSSARY 313 APPENDIX I Case Studies 333 Case Study I: Snow on Cholera 333 Case Study II: Working Through an Infectious Disease Outbreak 355

11 45175_FM_i_xx.qxd:Merrill 7/10/12 4:08 PM Page xi Table of Contents xi Case Study III: Common-Source Outbreak of Waterborne Shigellosis at a Public School 364 Case Study IV: Retrospective Analysis of Occupation and Alcohol-Related Mortality 371 Case Study V: Retrospective Cohort Study of the Association of Congenital Malformations and Hazardous Waste 374 Case Study VI: History and Epidemiology of Polio Epidemics 380 APPENDIX II Common Study Designs with Selected Measures of Association and Test Statistics 397 APPENDIX III Summary of Confidence Intervals for Evaluating Selected Hypotheses 399 APPENDIX IV Classification and Specialty Journals in Epidemiology 401 APPENDIX V Epidemiologic Associations and Societies 405 APPENDIX VI Selected Answers to Chapter Questions 407 INDEX 415

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13 45175_FM_i_xx.qxd:Merrill 7/10/12 4:08 PM Page xiii About the Author Ray M. Merrill, PhD, MPH, MS, is a professor of epidemiology and biostatistics at Brigham Young University. He is also an adjunct professor in the Department of Family and Preventive Medicine and the Department of Health Promotion and Education at the University of Utah. He is a former Cancer Prevention Fellow at the U.S. National Cancer Institute and a visiting scientist in the Unit of Epidemiology for Cancer Prevention at the International Agency for Research on Cancer, Lyon, France. He has won several awards for his research in epidemiology and is currently a Fellow of the American College of Epidemiology and of the American Academy of Health Behavior. He teaches classes in epidemiology and biostatistics and is the author of over 200 peer-reviewed publications and five books.

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15 45175_FM_i_xx.qxd:Merrill 7/10/12 4:08 PM Page xv Preface The field of epidemiology has come a long way since the days of infectious disease investigations by scientists such as Louis Pasteur, Robert Koch, and John Snow. Historically, the main causes of death were due to a single pathogen, a single cause of disease. Epidemiologists had the challenge of isolating a single bacterium, virus, or parasite. In modern times, advances in nutrition, housing conditions, sanitation, water supply, antibiotics, and immunization programs have resulted in a decrease in various infectious diseases but an increase in many noninfectious diseases and conditions. Consequently, the scope of epidemiology has expanded to include the study of acute and chronic noninfectious diseases and conditions. Advances in biology, medicine, statistics, and social and behavioral sciences have greatly aided epidemiologic study. This book was written as an introductory epidemiology text for the student who has minimal training in the biomedical sciences and statistics. Introduction to Epidemiology is based on the premise that the advanced analyses of empirical research studies, using advanced statistical methods, are more akin to biostatistics than epidemiology and, therefore, receive less attention in this book. Many recent books bearing the title of epidemiology are in fact biostatistics books, with limited information on the basics of epidemiological investigations or the study of epidemics. Epidemiology is unique from biostatistics in that emphasis is placed on completing the causal picture in human populations. Identifying causal factors and modes of transmission, with the assistance of statistical tools and biomedical information, reflect the primary aim of epidemiology. This book maintains that focus. Chapter 1 presents the foundations of epidemiology, including definitions, concepts, and applications. Chapter 2 covers historical developments in epidemiology. Chapter 3 looks at several important disease concepts in epidemiology. Chapters 4 through 6 focus on descriptive epidemiology. Several design strategies and statistical measures are presented. Chapter 7 presents design strategies and statistical methods used in analytic epidemiology. Chapter 8 covers design strategies and ethical issues relevant to experimental studies. Chapter 9 considers the basics of causal inference. Chapter 10 focuses on basic concepts and approaches used in field epidemiology. Chapter 11 presents chronic disease epidemiology. Chapter 12 presents epidemiology in clinical settings.

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17 45175_FM_i_xx.qxd:Merrill 7/10/12 4:08 PM Page xvii New to the Sixth Edition The sixth edition of this classic text, like its previous editions, continues its mission of providing a comprehensive introduction to the field of epidemiology. Emphasis is placed on the application of the basic principles of epidemiology according to person, place, and time factors in order to solve current, often unexpected, and serious public health problems. Direction is given for how to identify and describe public health problems, formulate research hypotheses, select appropriate research study designs, manage and analyze epidemiologic data, interpret study results, and apply the results in preventing and controlling disease and health-related events. Real-world public health problems involving both infectious and chronic diseases and conditions are presented throughout the book. Additions to this edition include a greater emphasis on epidemiology in international settings, additional study questions, expanded conclusions, as well as updated tables, figures, and examples throughout the text. Specific additions include a presentation of country-specific leading causes of death by income level; the important contributions to epidemiology by Alice Hamilton, Wade Hampton Frost, and Janet Lane-Claypon; clarification of allergies and inflammatory diseases and a description of Healthy People initiatives, with focus on the 12 Healthy People 2020 topic areas and associated health indicators; a description of how to compute a confidence interval for the standardized morbidity ratio; a revised section on population pyramids; a new section on death-to-case ratios; a new section on misclassification for case-control and cohort studies; descriptions of prophylactic trials and diagnostic and screening studies; a new section on pilot studies, and a presentation of three principles to guide research that involves human subjects (i.e., respect for persons, beneficence, and justice); a new section on statistical inference; a new section on preparing for fieldwork in a field investigation; and new material on mass screening and selective screening. This sixth edition offers an easy and effective approach to learning epidemiology, including case reports and news files. The case reports and news files represent applications

18 45175_FM_i_xx.qxd:Merrill 7/10/12 4:08 PM Page xviii xviii New to the Sixth Edition of commonly used research designs in epidemiology. The chapter topics were selected to represent the fundamentals of epidemiology. Learning objectives are presented at the beginning of each chapter, and the chapters are divided into concise sections with several examples. Figures and tables are used to summarize and clarify important concepts and information. Key terms are bolded in the text and defined. Study questions with descriptive answers are provided at the end of each chapter.

19 45175_FM_i_xx.qxd:Merrill 7/10/12 4:08 PM Page xix Introduction Epidemiology is a fun and challenging subject to study, as well as an interesting field to pursue as a career. Most undergraduate and graduate degree programs in public health, environmental health, occupational health and industrial hygiene, health education and health promotion, health services administration, nursing, and other health-related disciplines require a basic introductory course in epidemiology. Introduction to Epidemiology covers the fundamentals of epidemiology for students and practitioners. It is hoped that this book will be a useful and practical source of information and direction for students of epidemiology in the classroom and for those practicing epidemiology in the field. Readers of this book may be specialists in international projects in developing countries, industrial hygienists within major industrial plants, infectious disease nurses in hospitals and medical centers, chronic disease epidemiologists in government agencies, behavioral scientists conducting health epidemiological investigations, or staff epidemiologists in local public health departments.

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