Easy enough to ask, but the answers are becoming increasingly complicated. Today, as the public worries about emerging diseases and the word epidemic is part of the general discussion, epidemiology should be a basic component of medical training, yet often it is undertaught or even neglected. Concise and readable while also rigorous and thorough, An Introduction to Epidemiology for Health Professionals goes beyond standard textbook content to ground the reader in scientific methods most relevant to the current health landscape and the evolution of evidence-based medicine—valuable keys to better understanding of disease process, effective prevention, and targeted treatment. This volume:

Presents material accessibly for readers who may have not studied epidemiology.
Focuses equally in descriptive and analytic branches of epidemiology.
Demonstrates applications of descriptive and analytic methods in public health, genetic epidemiology, and clinical epidemiology.
Includes a "Sources of Error" section addressing problems in inference and decision-making, selection bias, and other common pitfalls.

In addition to its usefulness for graduate students in public health and medical students in clinical epidemiology, An Introduction to Epidemiology for Health Professionals is a timely reference for practitioners needing a refresher in this important discipline.

Therearemanygoodepidemiologytextbooksonthemarket,butmostoftheseare addressedtostudentsofpublichealthorpeoplewhodoclinicalresearchwithe- demiologicmethods. Thereisaneedforashortintroductiononhowepidemiologic methodsareusedinpublichealth,geneticandclinicalepidemiology,becausehealth professionalsneedtoknowbasicepidemiologicmethodscoveringetiologicaswell asprognosticfactorsofdiseases. Theyneedtoknowmoreaboutmethodologythan introductorytextsonpublichealthhavetooffer. Insomehealthfaculties,epidemiologyisnotevenpartoftheteachingcurri- lum. Webelievethistobeaseriousmistake. Medicalstudentsarestudentsofall aspectsofdiseasesandhealth. Withoutknowingsomethingaboutepidemiologythe cliniciansandotherhealthprofessionalscannotreadagrowingpartofthesci- ti cliteratureinanyreasonablycriticalwayandcannotnavigateintheworldof "evidence-basedmedicineandevidence-basedprevention. "Withoutskillsine- demiologicmethodologytheyareinthehandsofexpertsthatmaynotonlyhavean interestinhealth. Some health professionals may believe that only common sense is needed to conductepidemiologicalstudies,butthescienti cliteratureandthepublicdebate onhealthissuesindicatethatcommonsenseisofteninshortsupplyandmaynot thrivewithoutsomeformaltraining. Epidemiologic methods play a key role in identifying environmental, social, and genetic determinants of diseases. Clinical epidemiology addresses the tr- sitionfromdiseasetohealthortowardmortalityorsocialormedicalhandicaps. Publichealthepidemiologyaddressesthetransitionfrombeinghealthytobeingnot healthy. Descriptiveepidemiologyprovidesthediseasepatternthatisneededtolook athealthinabroadperspectiveandtosettheprioritiesright. Epidemiologyisabasic scienceofmedicinewhichaddresseskeyquestionssuchas"Whobecomesill?"and "Whatareimportantprognosticfactors?"Answerstosuchquestionsprovidethe basisforbetterpreventionandtreatmentofdiseases. Many people contributed to the writing of this book: medical students in Denmark,studentsofepidemiologyattheIEAEEPEsummercourseinFlorence, Italy,andstudentsofpublichealthinLosAngeles. Withouttechnicalassistance v vi Preface fromGitteNielsen,JenadeShelley,NinaHoheandPamMasangkaythebookwould neverhavematerialized. LosAngeles,California JornOlsen Odense,Denmark KaareChristensen IowaCity,Iowa JeffMurray Stockholm,Sweden AndersEkbom Contents Part I Descriptive Epidemiology 1 Measures of Disease Occurrence ...3 IncidenceandPrevalence ...4 Incidence...6 RatesandDynamicPopulations ...7 CalculatingObservationTime...9 Prevalence,Incidence,Duration ...10 MortalityandLifeExpectancy ...11 LifeExpectancy ...12 References...13 2 Estimates of Associations ...15 3 Age Standardization...19 4 Causes of Diseases ...23 References...28 5 Descriptive Epidemiology in Public Health...29 GraphicalModelsofCausalLinks ...33 References...35 6 Descriptive Epidemiology in Genetic Epidemiology...37 OccurrenceDatainGeneticEpidemiology ...37 ClusteringofTraitsandDiseasesinFamilies ...38 TheOccurrenceofGeneticDiseases ...40 References...41 7 Descriptive Epidemiology in Clinical Epidemiology...43 SuddenInfantDeathSyndrome(SIDS)...44 CytologicalScreeningforCervixCancer ...45 ChangesinTreatmentofJuvenileDiabetes ...46 References...47 vii viii Contents Part II Analytical Epidemiology 8 Design Options...51 CommonDesignsUsedtoEstimateAssociations...51 EcologicalStudy ...52 Case-ControlStudy...54 CohortStudy ...5 5 ExperimentalStudy ...56 Reference ...57 9 Follow-Up Studies ...59 TheNon-experimentalFollow-Up(Cohort)Study ...59 StudyingRiskasaFunctionofBMI ...60 LongitudinalExposureData...62 DifferentTypesofCohortorFollow-UpStudies...63 10 Case-Control Studies...67 Case-CohortSampling ...69 DensitySamplingofControls...69 Case-Non-caseStudy...71 PatientControls ...72 SecondaryIdenti cationoftheSourcePopulation ...74 Case-ControlStudiesUsingPrevalentCases...74 WhentoDoaCase-ControlStudy? ...77 References...78 11 The Cross-Sectional Study...79 12 The Randomized Controlled Trial (RCT) ...81 Reference ...