Epidemiological Studies: A Practical Guide

Epidemiological Studies Second Edition Following on in the footsteps of its acclaimed and popular predecessor, this new edition builds on the successful features that engaged readers of the first edition: it explains the nuts and bolts of epidemiology and serves as a handbook for those who wish to do epidemiology; it uses relevant exercises and examples, taken from real life, to illustrate how to set up a study; it aims to help produce valid results that will satisfy grant bodies, ethical committees and journal editors; ultimately it bridges the gap between theory and practice. By making the subject so easily accessible, it will be an excellent introduction for anyone who is training in epidemiology and public health, and for all those involved in medical research. This edition includes numerous improvements and several new chapters which will further enhance its appeal and usefulness. Epidemiological Studies A Practical Guide Second Edition Alan J. Silman The Medical School, University of Manchester and Gary J. Macfarlane The Medical School, University of Manchester           The Pitt Building, Trumpington Street, Cambridge, United Kingdom    The Edinburgh Building, Cambridge CB2 2RU, UK 40 West 20th Street, New York, NY 10011-4211, USA 477 Williamstown Road, Port Melbourne, VIC 3207, Australia Ruiz de Alarcón 13, 28014 Madrid, Spain Dock House, The Waterfront, Cape Town 8001, South Africa http://www.cambridge.org © Cambridge University Press 1995, 2004 First published in printed format 2002 ISBN 0-511-04221-3 eBook (netLibrary) ISBN 0-521-81097-3 hardback ISBN 0-521-00939-1 paperback First published 1995 Second edition 2002 Contents Scope of this volume Acknowledgements page xi xiv PA R T I I N T R O D U C T I O N 1 Scope of epidemiological enquiry and overview of main problem areas 1.1 1.2 What questions can epidemiology answer? What are the major issues in conducting epidemiological research? 3 3 7 PA R T I I M E A S U R I N G T H E O C C U R R E N C E O F D I S E A S E 2 Which measure of disease occurrence? 2.1 2.2 2.3 3 Comparing rates: between and within populations 3.1 3.2 3.3 v Incidence Prevalence Choice of measure Introduction Standardisation Comparison of rates over time 13 13 16 17 20 20 21 24 vi Contents PA R T I I I ST U DY I N G A SSO C I AT I O N S B E T W E E N R I S K FAC TO R S A N D D I S E A S E 4 Which type of study? 4.1 4.2 4.3 4.4 4.5 4.6 5 The ecologic study The migrant study The cross-sectional study The case-control study The cohort study Choice of study design Which measure of association? 5.1 5.2 5.3 5.4 5.5. Relative risks Odds ratios Attributable risks Precision of measures in association Categorisation of exposures 31 31 33 35 37 39 41 45 45 47 48 49 49 PA R T I V S E L EC T I O N O F P O P U L AT I O N S A N D SA M P L ES TO ST U DY 6 Studies of disease occurrence. I: Ident