Presentation on theme: "Chapter 2 Epidemiological Data Sources and Measurements"— Presentation transcript:
1 Chapter 2 Epidemiological Data Sources and Measurements Epidemiology & Biostatistics
2 Types of Data Used in Health Studies Denominator DataA definition of the population at riskExample: Smokers at risk for lung cancerExample: Men over the age of 40 who are in excess of 50 pounds or more over their ideal weight at risk of coronary artery disease.Women aged 70 and over who are calcium deficient and at risk of developing osteoporosis
3 Continued Numerator Data A definition of the events or conditions of concernExample: Lung CancerExample: Coronary Artery DiseaseExample: Osteoporosis/Broken hips
4 Methods of Data Collection United States CensusTakes place every 10 yearsAlso collects continuously data on births and deaths through the Dept. of Vital Statistics
6 The U.S. CensusA method of data collection used by the federal governmentCompleted every ten years in a year that ends with “0”Next census collection will be in 2010Last census collection was in 2000
7 U.S. Vital StatisticsBasically deals in birth and death of the populationLocal and state officials collect informationFederal government collates the information after it is collected
8 Cause of Death Immediate What event precipitated the actual death UnderlyingAny event that the immediate cause of death was a symptom of
9 ExampleHistory: Child is admitted to hospital after being struck by car. He is unresponsive and shows signs of blunt trauma to thoracic (chest) area. During ER triage and examination he begins to hemorrhage as a result of a aortic tear and subsequently dies.
11 CAUSES Immediate Underlying Aortic Tear (bleeds to death due to a ruptured aorta)UnderlyingCar accident caused blunt trauma(the car striking the child caused a blunt trauma which in turn tore the aorta)
12 Refer to Text Pp. 22 Table 2-1 What do you think? If someone dies of one of these diseases, is the disease the underlying or the immediate cause of death?Let’s discuss
13 EPIDEMIOLOGICAL REGISTRIES Disease RegistriesState disease specific registriesData from Third Party PayersVeterans Administration, etc.Novel RegistriesAustralian Rheumatoid Arthritis Database
14 Epidemiological Measurements Frequency – deals with numbersIncidence – number of occurrences (well: ill or live: dead)Prevalence – number of cases within a population at a given timeRisk – deals with proportion of people unaffected at the beginning of a study
15 ContinuedRates: Frequency of events that occur in/during a defined period of time.Generally the following rules are in playDecimal fractions are avoided as they are awkward in discussion (i.e. 1/100th of a death?)Numerator: rate of the frequencyDenominator: number of people at risk during period being studied/consideredConstant multiplier: usually 100 in order to get a percentage; 1000, 10,000 or 100,000 used for numbers less than “1”. Not used a lot.
16 Risk Versus Rate Risk denominator does not change Risk is the event itself, i.e. death, illness, etc.Risks are estimated by ratesRates denominator constantly changesRate is the # of times an event happensRate estimates risk when:Event occurs only once per individual during the studyProportion of population affected is smallTime interval of event is short
17 Types of Rates Incidence Rate Prevalence Rate Crude Rates Specific RatesDeath Rates
18 Maternal and Fetal Associated Rates Infant mortality rates: death of infants born aliveNeonatal and Post-neonatal Mortality Rates: death of infants a) during first 28 days of life (neo=new) and b) from 28th day to 1 year of life (post=after event).Perinatal mortality rates: deaths that occur around the time of birth (i.e. stillborn)Maternal mortality rates: death of a pregnant woman as a result of pregnancy related health issue
19 ConclusionPlease be sure and re-read this section we have covered a lot of ground but there is much more within the chapter for you to discover.QUESTIONS ???
22 Types of Surveillance Passive Surveillance Active Surveillance Routine data collectionPhysiciansClinicsLaboratoriesHospitalsExample: Infant Mortality rate in Duval County, Florida in January 2008Active SurveillancePeriodic reportsBy phone or visitLabor intensiveHealth departmentsExample: The insuring that TB patients are taking their medications as directed
23 Baseline Data Surveillance Baseline data is based on information that is considered the norm in terms of disease or health issues in a given area at a given time.Example: Cases of influenza that are reported in Houston County, Georgia during the months of October through April of the last 5 years.
24 Seasonal Variations of Disease Prevalence Depends on the route of transmissionExamples:Mosquitoes spread West Nile Virus in the summer monthsHeartworm disease in canines is more likely to occur during the summer months due to prevalence of mosquitoesLyme Disease is more likely to be contracted due to a) high population of Ixodes ticks and b) popular time for outdoor activities putting people at risk
25 Years? Calendar Year Epidemiologic Year Runs from January 1 to December 31stEpidemiologic YearRuns from the beginning of the month of the lowest incidence to the end of the month of the highest incidence.
26 Things to Know About Outbreaks Epidemic: Occurrence of disease at an unusual frequencyOne must know the normal rates at which diseases occur in order to spot an epidemic (One cannot recognize the abnormal if you do not know the normal)Syndromic Surveillance: Surveillance which is looking for unlikely symptoms that may identify possible bio-terrorist activity using biologicals.
27 How to Investigate a Suspected Epidemic Understand various types of epidemics:Epidemic: the unusual occurrence of diseaseEndemic: disease occurring regularlyEpizootic: disease outbreak occurring within animal populationsEnzootic: disease that is entrenched though not displaying change within an animal population
28 Elementary my dear Watson… Investigating an Epidemic:Establish a common diagnosisEstablish a case definition (criteria of the disease)Establish a given number of diagnosed casesThis is somewhat predicated by the number of cases of the disease normally seen in the area at the same time of the yearEstablish Time, Place and Person
29 The HypothesisThe development of a hypothesis should address three things:Source of infectionPattern of spreadMode of transmissionTesting of Hypothesis should be done by:Laboratory studiesCase Control studies
30 HISTORYA family spending the summer on a resort island, hires a cook and gardener to take with them for a total of eleven people. Shortly after arriving six of the eleven people fall ill with diagnosed Typhoid Fever. Soon after the outbreaks of Typhoid, the cook left for fear of her own life. Soon after with treatment, rest, good food and the pleasant tropical surroundings, the family began to recover from the illness. It was later discovered that the recently departed cook had worked for seven different families. During the course of her employment, 22 people were struck down with Typhoid Fever.
31 ? ? ? What was the source of the infection? What was the pattern of spread?What was the mode of transmission?
32 TYPHOID MARY Answers Source of Infection: The cook Pattern of Spread: Contaminated foodMode of Transmission: Oral IngestionTYPHOID MARY
33 Hypothesis Proved…Now What? Initiate control measures through interventionSanitationProphylaxisDiagnosisTreatmentControl/eradication of vectorsFollow Up Surveillance