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27 Cards in this Set
- Front
- Back
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What is Environmental Epidemiology? |
•The study of diseases and healthconditions (occurring in the population) that are linked to environmentalfactors. •These exposures are usuallyinvoluntary |
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Concern with populations |
•Environmental epidemiology studies apopulation in relation to morbidity and mortality.
–Example:Is lung cancer mortality higher in areas with higher concentrations of“smokestack” industries? |
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Use of observational data |
•Epidemiology is primarily anobservational science that takes advantage of naturally occurring situations inorder to study the occurrence of disease.
•Experimental methods usually not usedbecause of ethical issues due to potential dangers. |
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Methods for study designs |
•Characteristic study designs usedfrequently in environmental epidemiology: –Cross-sectional –Ecologic –Case-Control –Cohort |
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Classes of epidemiological studies |
•Descriptive-depiction of the occurrence of disease in populations according toclassification by person, place, and time variables. –Demographic characteristics –Geographic locations –Decade, year, month, etc. •Analytic-examines causal (etiologic) hypotheses regarding the association betweenexposures and health conditions .–Natural experiment- naturally occurringcircumstances in which subsets of the population have different levels ofexposure to a supposed causal factor. |
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Cluster |
•The occurrence of a group of cases of adisease close together in time and place at the time of their diagnosis. |
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Measure of disease frequency |
•Prevalence •Point prevalence •Incidence •Incidence rate •Case fatality rate |
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Prevalence |
•Refers to the number of existing cases ofa disease, health condition, or deaths in a population at some designated time |
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Point Prevalence |
•Refers to all cases of a disease, healthcondition, or deaths that exist at a particular point in time relative to aspecific population from which the cases are derived.
PointPrevalence = Number of persons ill/Total number in the group ata point in time |
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Incidence |
•Theoccurrence of new disease or mortality within a defined period of observation(e.g., week, month, year, or other time period) in a specific population. IncidenceRate = Number of new cases/Total population at risk over a time period xmultiplier (e.g., 100,000) |
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Case Fatality Rate (CFR) |
•Provides a measure of the lethality of adisease.
CFR(%) = Number of deaths due to disease “X” /Number of cases of disease “X “during the same time period x 100 |
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History (Epi) |
•Sir Percival Pott- observed that chimneysweeps had a high incidence of scrotal cancer. •John Snow- father of modern epidemiology.Linked a cholera outbreak with the Broad St. water pump |
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Experimental Study Design |
implemented as intervention study thatinvolves intentional change
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Case Series |
information about patients who share adisease in common is gathered over time
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Cross-Sectional |
•examines the relationship betweendiseases
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Ecologic |
•units of analysis are populations orgroups of people, rather thanindividuals |
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Case Control |
•participants are defined on the basis ofthe presence (cases) or absence (control) of an outcome of interest |
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Cohort |
•classifies subjects according to theirexposure to a factor of interest and then observes them over time to documentincidence of disease or other health events |
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Odds Ratio Equation |
•OR-measure of association between exposure and outcome used in case controlstudies. AD/BC. An OR >1 (when statistically significant) suggests odds ofdisease are higher among exposed persons than those not exposed. |
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Cohort Study |
•Longitudinal- subjects followed over longperiod of time –Prospective-participants certified as being free from the outcome of interest –Retrospective(historical cohort)- reconstructs data about persons in the past•Relative Risk-measure of association |
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Relative risk |
The ratio of the incidence rate of adisease or health outcome in an exposed group to the incidence rate of thedisease or condition in a non-exposed group.
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RR Equation |
RR = A/(A + B)
C/(C + D) Notes: When an association isstatistically significant: RR >1 indicates that the risk of disease isgreater in the exposed group than in the nonexposed group. RR<1 indicates possible protectiveeffect. |
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Epidemiological Triangle |
Host Agent Environment |
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Hill's Criteria of Causality |
•Strength
•Consistency •Specificity •Temporality •Biological gradient •Plausibility •Coherence |
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Bias |
•Recall bias-cases may remember anexposure more clearly than controls •Systematicbias-distortions that result from procedures used to select subjects |
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Healthy Worker effect |
•Refers to the observation that employedpopulations tend to have a lower mortality experience than the generalpopulation.
•The healthy worker effect could introduceselection bias into occupational mortality studies. |
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Limitations of Epidemiological Studies |
•Long latency periods
•Low incidence and prevalence •Difficulties in exposure assessment •Nonspecific effects |
