Comm Test 3: epidemiology Flashcards
- detective work, learn how to investigate
The study of distribution(where it goes, who what where and when) to and determinants(what, who, where , when, why, and how) of health and disease. Looking at causes - find pt zero= signs and symptoms first, walked on plane with it/ go out to who is exposed making a web of causation, map out
-Integrates principles of scientific research.
-Accurate assessment and correct diagnosis.
-Aimed at finding cause of health or disease.
Describes disease patterns according to person, place, and time- determine where pt 0 have been and who has been in contact with
Epidemiology
cause and treatment, determinants
Analytical epidemiology
- going out after all of the determinants and focused on treatment/ taking analytical epi and applying it to a situation
Applied epidemiology
types of epidemiology
descriptive
analytical
applied
questions that we ask
Distribution
Distribution--who, what, where, and when Person – Who is affected? Event – What happened? Place – Where did this happen? Time – When did this happen?
Determinants
may have to take a long history
could have gotten it in a hospital
How did the event occur?
Why did the event occur?
- always have to have host=pt 0, agent=tb, and environment= where it spread, precipitate this
next distribution then determinant
Epidemiological Triangle
- good positive factor, what do you have going for you
- Agent – Etiological Factors
* epidemiological triangle
- med=chem bc suppression of immune system, bacteria, childhood diseases =shingles: still have virus in it, not as immune as we thought we were
Lifestyle factors= smoking: limit immune system
Equipment and machines in health care facility not cleaned well
Vegs and fruit that are not washed well have organisms
. Agents of Disease
epidemiological triangle
– Intrinsic Factors: hard to modify Genetics Age Gender Ex: women more susceptible to UTI Ethnicity General physical condition- to a point Behaviors- drinking, smoking, enough sleep
Host
= Extrinsic Factors- things you can’t control
Ex: Work conditions, Weather, Food sources, Population density, War= agent orange bomb, economic development= third world country that doesn’t have agriculture or fresh clean water: more susceptible to a disease
Environment
- plot all factors that affect patient 0
ask about agent, enviro, host
Web of Causation
: illness type of issues
Morbidity
Sometimes underreported due to lack of surveillance.
– the occurrence of new cases of a disease or condition over a period of time relative to the size of the population at risk for that disease or condition during the same period of time.
-plot number of cases in each month to determine most prevalent
-want to know if it is spreading or getting worse
Most sensitive indicator of changes in health
-Can be used with chronic disease Ex: heart failure, 5 or 10 year , still valid , can use just enlarge period of time
-Usually used for short term, acute disease
* risk rate
* new cases during a given time not old / average population at geographic are
Ex: 2003 335,105 causes of gonohrea where reported in us. 2003 us pop was 290788976
Incidence Rate
Morbidity
don’t confuse with incident( pop period)
The number of new cases of a disease in those who have been exposed to the disease. Ex: grade school, established first statistic then new cases of people exposed on the plane after intial
-Used when the population is exposed to an infectious disease at a given time and place.
*probability risk rate
* highly specific person limited by specific place and time period is brief
Ex: 75 people attended church picnic 46 dev gi illness
Attack Rates-
Morbidity
Measures existing disease in a population at a given point in time relative to the population at the same point in time= how much it goes up
Influenced by the number of people who experience the disease and duration of the disease.
Increases when the incidence rate or duration increases.
*risk and duration
* portion of people in population who have a particular disease new and old cases/ population in the area
Prevalence Rate
Morbidity
Refers to routine collection of birth and death rates. New or end of life issues Not to be confused with morbidity rates. Crude death rate Age-specific rate Proportionate mortality rate
Mortality Rates
Estimate of the risk of death for a person in a given population for that year. Ex: newborns with down syndrome what is the rate of survival
Number of deaths from any cause during a certain time interval (6months)
Use mid-year interval (June 30th)
Affected by variables of age, race, SES
Crude Mortality (death) Rate
- living in town with aging pop risk goes up because see more deaths there
- AA higher risk of males in coronary artery disease
- not have access to resource that they have, lifestyle issues
Crude Mortality (death) Rate
age
race
ses
Number of deaths among a given age group per mid-year population as compared to the estimated population.
Characterizes a particular age group in the population.
Subgroups. 65-75 group males with heart disease
Age-Specific mortality Rates
all deaths resulting from a specific cause relative to deaths from all causes.
Total number of death from any cause/ then death of specific cause
Ex: 100 deaths you had 20 deaths from CHF calculated in 100 the ratio is 1-5
-Identifies areas for intervention aimed at reducing deaths. HP 2020, LHI
-Must be taken into context.
Proportionate Mortality Ratio
concept of risk
risk factor
attributable risk
relative risk ratio
- Probability of an adverse event
Risk
- Exposure to an adverse event
Risk factor
- Estimate of disease burden in a population, likely to be infected
Attributable risk
Excess risk caused by the risk factor
Relative risk ratio-
- pre-pathogenesis
* immunizations
Primary prevention
- screenings
* aimed at early intervention
Secondary prevention
- rehab and restore
Tertiary prevention
Purpose = identify risk factors at the earliest stage
-don’t have to be done every year
Screening
- it will produce results each time, suspect someone of having we will know and will determine results
Reliability screening
- are the results accurate
Validity screening
- correctly identifies those persons with the disease, has to be right level, won’t use till other dx test have been done, overly can have false-positives
Sensitivity
screening
- correctly identify person that does not have the disease , may get false- negatives when really sensitivity is to low= they really do have the disease
Specificity
screening
- breaking down the proportion of person of a positive test that actually have that
Positive predictive value
screening
- proportion of person of a negative test that don’t have it
Negative predictive value
-not focused on intervention, tells story about what happened, focus on distribution of it how far it got and who go it
distribution of health outcomes using person, place, & time.
-Narrative regarding what happened from beginning to end
-Time affected by secular trends
-Time affected by point epidemic
-Does not focus on clinical intervention.
-Based on surveillance data.
Descriptive Epidemiology
- Aims to find cause and treatment.
determinants – how and why? - Factors that influence observations of health and illness.
- Must have observational data from descriptive studies or conduct observation
Analytic Epidemiology
analytic studies
cohort
retrospective cohort study
- type of prospective, long term(longitudinal) and requires follow up
*Prospective watch people for a while and see if disease dev
-best estimate of disease incidence and risk
Reduces bias because waiting to see if it happens
study multiple affects
Disadvantage: long follow up=attrition rate, large number of subjects, expensive, exposure factors may change, doesn’t work well with rare disease= not enough of them
Cohort study
Analytical
– compare persons with the disease to those that do not, rigorous criteria to be able to participate, can be a control group
-questions the causality better, less data and resources
Retrospective cohort study
Analytical
retrospective cohort
case control
cross sectional
can estimate the risk, lesser number of subjects, less money, quicker, can investigate more than one exposure, best design for rare disease, best for disease with a relatively clear onset
Disadvantage: attrition rate
Case-control advantage
Retrospective cohort
Analytics
correlation studies, relationship between the cause of disease, does not calculate the risk cause or incidence rate, can’t definitively substantiate the cause
Quick to plan and conduct, hypothesis is generated Ex: what causes disease
Address causality better
Disadvantage attrition rate
Cross-sectional:
Retrospective cohort
Analytical
Can’t calculate the risk incidence or prevalence, not good for rare disease
Cross-sectional: Disadvantage
- investigator initiates a treatment or intervention to influence the risk for or course of disease, test whether interventions can prevent disease or improve health , person is randomly assigned to a particular group an intervention is applied and effects are measured
Experimental design
- evaluates the effectiveness of an intervention
Best way to show causality
Disadvantage: is it fair to withhold treatment if treatment truly appears to have effect, expensive in terms of time, personnel, facilities, and supplies
Clinical trial
Experimental
experimental epidemiological studies
Clinical trial
. community trials
- investigation determines what the exposure or intervention will be, deal with health promotion and disease prevention rather than treatment of existing disease,
intervention is usually undertaken on a large scale and unit of treatment is a region, or group rather than individuals
-involve educational, programmatic, or policy interventions - best means for testing whether changes in knowledge or behavior, policy, programs or other mass interventions are effective
. community trials
advantage
experimental
- may take years for evident,
- Comparable populations without similar interventions for comparative analysis are often difficulty to find
- it is difficult and unethical to prevent the control from making use of generally available information=effectively making them different from the intervention
- can be expensive, require a large staff, have complicated logistics, and need extensive communication about the study
. community trials disadvantage
experimental
subjects are randomly assigned to groups, randomization is used, best way to show causality bc of the objective way in which the subjects are assigned, prospective and provide the clearest evidence of correct temporal sequence / double blind study
experimental group-
avoids bias, treatments are assigned to pts so that all possible treatment assignments have a predetermined probability but neither subject nor investigator determines the actual assignment
Randomization:
experimental group
-strong association between a potential risk factor and an outcome supports a causal hypothesis
Strength of association
causality
causality
Strength of association
- Consistency of findings
- Biological plausibility
- Demonstration of correct temporal sequence
- Dose-response relationship
- Specificity of the association
- Experimental evidence
- repeated findings of an association with different study designs and in different populations strengthen a causal interference
Consistency of findings
causality
- demonstration of a physiological mechanism by which the risk factor acts to cause disease enhances the causal hypothesis, conversely an association that does not initially seem defensible may later be discovered to be so
Biological plausibility
causality
for a risk factor to cause an outcome, it must precede the onset of the outcome
Demonstration of correct temporal sequence
causality
the risk for developing an outcome should increase with increasing exposure (either in duration or quantity) to the risk factor of interest EX: more woman smokes during pregnancy the greater the risk for delivering a low birth weight infant
Dose-response relationship
causality
-the presence of a one to one relationship between an agent and a disease, this criterion grows out of the infectious disease model in which it is more often though not always satisfied and is less applicable in chronic diseases
Specificity of the association
causality
- experimental designs provide the strongest epidemiologic evidence for causal association but they are not feasible or ethical to conduct for many risk factor disease associations
Experimental evidence
causality
Epidemiologic triangle
Agent host environment
fruit and veg wash well, certain med, exercise, vitamins, clean air, Things those are good…
B. Agents of Health
Morbidity rates
- incidence
- attack
- prevalence
