What is "ClinicalEpidemiology?" JOHN M. LAST GUEST EDITORIAL rc r SSEEKhere to make two points: first,that the term "clinicalepidemiology" is an oxymoron;second, that the uncriticalenthusiasm with which this activityis beingembraced in manymedical schools constitutes a dangerto health. Epidemiologyoriginally meant the cSe*9Xs scientificstudy of epidemics,implicitly communicable diseases.A few yearsago, an internationalpanel agreed,not without some argument,on a moderndefinition: the study of the distribution and determinantsof health-relatedstates and eventsin populations,and the applicationof this studyto controlhealth problems (i). The phrase "health-related"is therebecause epidemiologists study car-driving hab- its, physicalfitness, pregnancy and manyother phenomena that arenot diseases.And the finalclause is therebecause Zbigniew Brzezin'ski per- suadedme that it would make no sense to study the distributionand determinantsof such a conditionas malaria,or any other condition, withoutdoing something to controlit andevaluate the control measures. The term"clinical epidemiology" was firstused 50 yearsago byJohn R. Paul,who definedit as "a marriagebetween quantitative concepts used by epidemiologiststo study diseasein populationsand decision- makingin the individualcase which is the dailyfare of clinicalmedicine" (z). This definitionimplies that cliniciansshould consider the facts de- rivedfrom population-based studies of clinicalconditions before deciding what to do aboutindividual patients. If "clinicalepidemiology" means using past experienceto informand guidedecisions about care of individualpatients, it is as old as medicine; its roots are discerniblein the writingsof Hippocrates.This activityis clearlyessential to patientcare, but we need a new wordto describethe intellectualprocesses involved, because epidemiology is somethingal- togetherdifferent; appropriation of theword in thisway with a qualifying 159 Palgrave Macmillan is collaborating with JSTOR to digitize, preserve, and extend access to Journal of Public Health Policy ® www.jstor.org i6o JOURNAL OF PUBLIC HEALTH POLICY * SUMMER 1988 adjectiveby clinicalscientists devalues the scienceof epidemiology.Such a devaluationcan adverselyaffect health policy, which must always rely on epidemiology.The infiltrationof medicalschools by clinicianswho describethemselves as clinicalepidemiologists but arereally practicing clinicaldecision analysis could have seriousconsequences -physicians who lacka populationperspective may be verygood at clinicaldecision- making,but maynot necessarilycomprehend (or care much about) im- portantcommon health problems of the communitiesin which they practice. "Clinicalepidemiology," furthermore, tends to medicalize healthin an erawhen we shouldbe encouragingpeople to takerespon- sibilityfor theirown health. In the I98os, "clinicalepidemiology" is beingvigorously championed by clinicalscientists who seembent on givingepidemiology a new mean- ing.They offer plenty of definitionsof clinicalepidemiology. Patient care is centralto DavidL. Sackett'sdefinition: "The application, by a physi- cian who providesdirect patient care, of epidemiologicand biometric methodsto the studyof diagnosticand therapeutic processes in orderto effectan improvement in health"(3). Taken literally, this definition would excludeall who lackmedical qualifications, and would exclude applica- tion in publichealth. Sackett is reallydefining clinical decision analysis. Theproper distinction between clinical decision analysis and epidemiol- ogy is thatepidemiology is concernedwith the studyof diseaseor health- relatedphenomena in a definedpopulation, even if it is a populationof patientsrather than a community-basedpopulation with numerator and denominatorin the conventionalepidemiologic sense. There is nothing wrongwith this;much of ourrecently acquired understanding of causal and risk factorsfor manyrare conditions has come fromcase-control studies,often of quitesmall numbers of cases.But I get uncomfortable when "clinicalepidemiology" applies to studiesof a singlepatient, as in "N of one" studies(4) whereinsuccessive regimens are randomly allo- catedto a patientand the outcomesof eachregimen are assessed. "N of one" studiesare elegant and effective.But it is inappropriateto use the wordepidemiology in thiscontext. We need a differentword to describe this branchof clinicalscience. Sucha narrowview of epidemiologywould saddenthe foundersof theEpidemiological Society of London,most of whomwere public health workers,and saw epidemiologyas a disciplinethat existed primarily to protectand promotethe publichealth (i). Therewere distinguished cliniciansin thisSociety, however, whose clinical wisdom was enlightened LAST * WHAT IS "CLINICAL EPIDEMIOLOGY?" I6I by epidemiologicalinsights; they includedRichard Bright, Thomas Ad- dison and BenjaminBrodie; but the realthrust of the Societywas popu- lation-based,as perusalof its Transactionsmakes clear. ClinicalEpidemiology is the title of at least five recentbooks, if one in Frenchis included(6-io). All haveuseful, often importantthings to say;but all leaveout someaspects of whatmost epidemiologists consider to be integralparts of the discipline,and a coupleare hardly recognizable as epidemiology. Wordsare our servants,not our masters,and in the Englishlanguage their sense and meaningnever stop evolving.Words are also our most sensitiveand precise instruments, the sine qua non of scientificcommuni- cation.It is unfortunatewhen a restrictiveor differentnew meaningis conferredupon a word that has a long-standingand widely accepted usage-it is not necessarilyNewspeak, but is avoidable.Alvan Feinstein recognizedthis when he coinedthe word "clinimetrics"(i i) to describe the scienceof clinicalmeasurement. This word best describesmany ac- tivitiesthat are discussed at lengthin someof the new bookson "clinical epidemiology"(7-9), and it is the titleof Feinstein'slatest book (i z). Its Frenchequivalent, clinimetrie, is the subtitleof the excellentnew book by Jenicekand Cleroux(9). I believethat clinimetricsenriches the lan- guage,as biometrydid. None of the new bookson "clinicalepidemiology" meet the needfor a basictext that studentscan use when they arelearning the scienceand art of epidemiology(some of them don't even describecoherently the featuresof eithercohort or case-controlstudies, let alonethe use of vital statistics,which all of themignore). What they all makeclear is the need that I havealready mentioned, for a new wordor phraseto describethe intellectualprocesses that these books expound. Epidemiology they ain't, and "clinicalepidemiology" is an inappropriate,pretentious, and-most important- internallyinconsistent term to apply.It is internallyinconsis- tentbecause epidemiology refers to populations,and "clinicalepidemiol- ogy" often refersto individualpersons. Thereare grounds for realconcern, moreover, about the prospectsof a takeoverof medicalschool teachingand the researchagenda of epi- demiologyby clinicalepidemiologists. I applaudthe teachingof epide- miology in a clinicalsetting, perhaps the most significantadvance in clinicalteaching in my lifetime.But if this leadsto the abandonmentof non-clinicalteaching of epidemiologyand relateddisciplines and con- cepts,the next generationof physicians,and the societythey have been i6z JOURNAL OF PUBLIC HEALTH POLICY * SUMMER 1988 trainedto serve,will suffer.Medical sociology, social demography,com- munity-basedpreventive medicine and health promoting activities are inextricablyintertwined with epidemiologicteaching and practice;they are remote from, and might as well not exist for all the mention they receive in these new textbooks on "clinicalepidemiology," which also say little or nothing about health and its determinants. Health is, of course,too importantto be left to the clinicians.Clinicians are at best usually indifferentto, often covertly,even overtly,hostile to preventivemedicine, maybe still more hostile to the concept of health promotion. In the I98os, we have seen the birth of new concepts of health promotion, a centralfeature of which, enshrinedin the definition of health promotion (I3) and in the Ottawa Charter(I4), iS enabling people to take responsibilityfor their own health. If the only pertinent teaching is provided by clinicians-physicians who wear white coats, carry stethescopesand work in hospitals-there are real risks that these concepts will become medicalized just as we are attempting to return responsibilityfor health to the people. I find it difficultto visualizethe researchagenda for healthpromotion as it might be conductedby clinical epidemiologists.Who wants to study healthwhen they can study disease? Is researchon health promotion possible without the participationof epidemiologists?Are medicalschools to remaindisease palaces in the era of "healthfor all"? What if population-basedsurveillance and disease control activities cease to be part of medicaleducation? Already there are medicalschools where little or no attention is paid to these essential features of public health services.Do graduatesfrom such schools realizetheir obligation to reportcertain communicable and other diseases,or why it is important that they provide precise diagnostic information on death certificates? They may know some sophisticatedtricks that enliventheir presentations at grand rounds, they may have an enlightenedunderstanding of statis- tical tables that appear in articles in journals. But they may not know how to assess the health problems of the communities in which their