CHAPTER OUTLINE Basic Concepts in Public Health

1 35 CHAPTER2 Basic Concepts in Public Health Marion Willard Evans Jr., DC, PhD, CHESDEFINITIONS IN Public HEALTHP ublic Health , as defined by C. E. A. Winslow, a leading figure in the history of Public Health , is the science and art of preventing disease, prolonging life,and promoting Health and efficiency through organizedcommunity efforts for the sanitation of the environ-ment, the control of community infections, the educa-tion of the individual in personal Health , the organizationof medical and nursing services for the early diagnosisand preventive treatment of disease, and the develop-ment of the social machinery which will ensure toevery individual in the community a standard of livingadequate for the maintenance or improvement was not a bad definition for 1920. Today theAmerican Public Health Association (APHA) states thatpublic Health is the practice of preventing disease andCHAPTER OUTLINED efinitions in Public HealthTerms Used in Public HealthReportingCausation and Sir Austin BradfordHill s Criteria Assessment of Risk and Occurrenceof DiseaseRates Reported in Public HealthMeasuring for Causation and Risk AssessmentRisk DifferenceRisk RatioPreventionThe Mission of Healthy People in the Prevention of DiseaseScreening Counseling Patients on BehaviorChangeStages of Change Health Belief Modelpromoting good Health within groups of people, fromsmall communities to entire furtherstates it includes Health professionals from many fieldsworking together with the common purpose of protect-ing the Health of a population.

2 The goal of any community, or Health care providerfor that matter, should be to prolong the number ofyears of healthy life of the population it represents orcares for. With that goal in mind, people, social infra-structure, government aid to those most in need, andinvestigation of disease outbreaks may all play a role inthe Public s Health . Public Health uses the trends and oc-currences of disease in our populations and populationsubsets to infer the riskof disease for individuals. Tosome degree, the basis of risk or a risk factor(makingone more susceptible to a disease) takes its originloosely from the work of Koch. Koch s postulates lookedEcological Model of HealthPromotionWorking with Patients TowardBehavior ChangeLearning More About the BehaviorChange 10/12/09 5:51 PM Page 35 Jones and Bartlett Publishers, LLC. NOT FOR SALE OR DISTRIBUTION some diseases.

3 Race, socioeconomic grouping, nationality,ethnicity, and where one lives in proximity to the equatormay be a risk factor for certain diseases. Hypertension ismore prevalent in Blacks than Whites; that is, there areproportionally more existing casesof the disease amongBlacks than Whites, which is the definition of the termprevalence. Living in an area of the country where sun ex-posure is greater more days of the year may increaserisks of skin cancer, and living where there are fewerdays of sun could reduce the amount of vitamin D onehas circulating in the blood, which is now thought to in-crease risks for a host of , it is felt thatthere is a web of causation for most chronic diseasessuch that few instances exist where a single risk factorcauses a disease to occur. Epidemics occur when there are a large number of casesof a disease that are out of proportion with what is nor-mally expected to be seen for that time, place, or actual number may vary depending on the type of dis-ease or the population that has been exposed.

4 For in-stance, in a country where there is a high prevalence ofmalaria, a disease caused by a parasite in the blood carriedby mosquitoes, a few extra cases may be meaningless, butin Panama City Beach, Florida, during Spring Break, even ahalf-dozen cases would sound an alarm. That is becauseeven in Florida, malaria is not seen as an endemicdisease;that is, a disease that is constantly present in the commu-nity or population. Unfortunately, diseases like human im-munodeficiency virus or acquired immune deficiencysyndrome (HIV/AIDS), influenza, hepatitis, and others areconsidered endemic in the United States. Among those diseases endemic in a society, occasionallythere are dramatic spikes in the numbers that are higherthan those expected to be seen in the community or is known as an outbreak. Any occurrence of an en-demic disease that is out of proportion to what is ex-pected may be seen as an outbreak.

5 Certainly, an increasein a disease occurrence that is rarely seen or thought to beeradicated would also constitute an outbreak, and evenone case of the latter may signal serious Public healthconcerns. The Centers for Disease Control andPrevention (CDC) tracks thousands of outbreaks each yearin the United States and more informationon outbreak investigations, go to Terms Used in Public Health ReportingNumerous terms are used to describe Public healthevents, risk levels, and causes of disease. Among the morecommon are morbidity, mortality, prevalence,and inci-dence. Morbidity is the number of people suffering from aat diseases caused by living organisms and stated that ba-sically the following four relationships must occur re-garding causes of disease: 1. One must observe the [causative] organism inevery case of the It must be able to be grown in a pure The pure culture must, when inoculated into asusceptible host animal, reproduce the The microorganism must be observed in, and recov-ered from, the experimentally diseased s Concepts would be great if they could be ap-plied to every disease state, but how can one apply theseto chronic diseases that take years to develop and per-haps are due to multiple causes or risks?

6 Unfortunately,they can t. This brings up the concept of risk factors are those exposures or causal agents thatmake one more likely to suffer a disease or Health prob-lem. Although a risk factor may cause a disease if present,it may not actually be the true cause. The presence ofother factors may be necessary to cause the disease tooccur. One can use tobacco as an example of how one riskfactor can predispose a person to several diseases at onetime. Friis and Sellers point out that risk factors havethree The frequency of the disease varies by categoryor value of the factor. Example: Using smokingand lung cancer, they state the relationshipbetween smoking and cancer the more onesmokes, the greater the riskof The risk factor must precede the onset of thedisease. Example: Using the same lung cancerand smoking issue, they state if a smoker startedsmoking after developing lung cancer, it wouldbe wrong to label smoking the cause of The observed association must not be due to anysource of error.

7 There are always points at whicherrors may be introduced in trying to assesscauses of disease. Examples: Errors can occur inthe selection of the study participants, in themeasure of exposure and disease, and, of course,in statistical to a risk factor may occur due to actions or be-haviors one adheres to or may simply be inherent to theindividual due to the genetic cards they have been example, we know that prostate cancer is alwaysgoing to occur in males and cancer of the cervix in fe-males. This demonstrates that simply being born intoone gender category or the other increases one s risk for36|INTRODUCTION TOPUBLICHEALTH 10/12/09 5:51 PM Page 36 Jones and Bartlett Publishers, LLC. NOT FOR SALE OR DISTRIBUTION disease at a given time. It is related to illness. Mortalityisthe number of people who have died from a disease. The two most common measures of disease in popula-tions are prevalence and incidence.

8 Sometimes both termsare used in the description of a disease or disease out-break. Prevalence, which has already been mentioned, isthe number of people who have a disease at a given time;that is, the number currently suffering from the disease ordisorder. Incidence, on the other hand, is the number ofnew cases of a disease. One may hear a news report of theincidence ratesof a disease, such as influenza, being higherthan usual for the year. This indicates the number of newcases is higher than what is typically expected, whereas areport indicating increased prevalencewould mean thenumber of existing cases is higher. Epidemiologyis the science that looks at the relation-ships between diseases occurring in populations andgroups, typically in an attempt to reduce risks and compress morbidity into the last years of the popula-tions life span. Life spanis the limit of natural life suchthat through all supports and efforts one has lived aslong as is possible.

9 Life expectancymeans somethingdifferent, in that this term applies to the average lengthof life one may live based on gender, race, where onelives, and so on. Public Health scientists and epidemiol-ogists feel that the current life expectancy is not equal tothe possible life span; that is, we don t live as long as wecould live due to unnecessary risks that are taken andother factors that are typically controllable through be-havior, lifestyle, and environmental changes. In theUnited States, overall life expectancy is about 78 years, although women typically live longer than , the life expectancy of women in the UnitedStates is about 80 years and for men, and Sir Austin Bradford Hill s Criteria Causation or causal factors in the investigation of a dis-ease occurrence or outbreak can be difficult to all, not all diseases are associated with a knownexposure to a risk factor, nor do all diseases manifestthemselves shortly after exposure to even a known riskfactor.

10 For instance, it is well established that there is anassociation between smoking tobacco products andlung cancer. But how long does it take to get cancer?Cancer in general has what is known as a long latency pe-riod; that is, from the time one is exposed to a sub-stance known to cause cancer, called a carcinogen,sometimes it is years before one actually develops thedisease. During that time, multiple factors may comeinto play that could affect the individual s risks. In the 1960s, the link between smoking and cancerwas reported by the Surgeon General in a report titled,Smoking and Health , Report of the Advisory Committee tothe Surgeon General of the Public Health ,perhaps the most noted acknowledgment of this reportcame from Sir Austin Bradford Hill, a former professor ofstatistics at the University of London. In an address to theOccupational Medicine Section of the Royal Society ofMedicine in 1965, Hill gave a speech in which he outlinedthe criteria he suggested were essential when trying todetermine causation.