knew importance of enviroment & behavior
identified key risk factors that epidmiologist use today
left out quantifcation-baisis for determining eitology
Hippocrates
father of medicine
grandfather of epidemiology
hippocrates
why it comes and when it hits some die, others live?
theroies about epidemiology
Why those who survive, some get sick and others dont?
theories about epidemiology
Why of those who get sick some recover faster than others who diesease remains a while before survival?
theories about epidemiology
still an idea about disease around in present day
Gods are responsible for disease
diseases are caused by smelly air
comes from decaying soil
miasma theory
introduced quanitification
biological phenomena such as birth and deaths varied in predictiable ways (can be used to qantify disease)
john graunt
father of biostatisitics
John Graunt
first person to put into practice the principles of epidemiology
John Snow
father of epidemiology
John snow
Principle theories of Epidemiology?
Distrubution of Disease occurances
determination of disease etiology
control of disease occurance
leader in developing health and vital statisics records
first to demonstrate vital statistics and surveillance
(watchfullness over the distribution and trends of incidence through the systematic collection consolidation and evalutaion of morbidity reports and other relevant data)
William Farr
father of surveillance
william farr
first to take a stand aganst cross contamination in hospitals
infection control
ignaz semmeiweis
father of hospital epidemiology
ignaz semmiweis
deffinition of epidemiology
(word for word)
epidemiology is the study of the distribution and determinants of health realated states or events in specific populations and the application of this study to the control of health problems
deffinition of an epidemiologist
(word for word)
an investigator who studies the occurance of disease or other health related conditions or event in a defined population or the control of disease in populations
subspecialties of epidemiology
clinical
infectious disease
chronic
psychiatric
enviromental
pharmaco
social
definition of an epidemic
an increase in the number of cases over past experience for a given population time and place
what is the name for a graph showing distribution of disease outbreaks?
epidemic curve
list the recipe for an epidemic?
1. increase amout of a pathogen agent or toxin material
2. exposed and susceptible persons
3. commom circumstances which lead to occurence of an epidemic
a. susceptible are introduced to epidemic
b. a new pathogen is introduced
c. change in behavior, sexual or cultural practices
d. host altered by drug induced immunosuppresent or nutrition
list the steps of an outbreak investigation?
define epidemic
examine the distribution of cases
look for the combination interactions of relevant variables
develop hypothesis
test the hypothesis
recommend control measures
description of define the epidemic
find case
find denominator
calcualte attack ratio
distribution of cases
look for combination of variables
devlop hypothesis
test hypothesis
control measure
epidemiological triad
host natural shelter for the organism or agent
agent toxins that is usually associated with the occurance of the disease
envrioment medium in which the disease occurs
disease will not occur unless three are present
herd immunity to kill off certian diseases
uses of epidemiology
establishing causation
study of natual history of disease
describing the health status of population
person time
disease free time
definition of health
health is the state of complete physical, mental, social and spiritual well being and not merely the absence of disease or infirmity
measurement of validity
a variable is vaild measure of a property if it is relevant and appropriate as a representation of that property
rate three types
crude specific adjusted
two types of standardization
direct indirect
two measures
incidence prevalence
prevalence of specific disease
prevalence is the proportion of the population at risk affected by the disease at a speicifc point in time
point prevalence
specific point or period in time
# of exsiting cases during a time period (ie the numerator)
average population size durring a time period (exsiting cases + incident case) ie denominator
period prevalence
factors that influence prevalence
fatality
incidence
treatment
diagnosis
migration
reporting
duration
when a new treatment is developed that prevents death but does not produce recovery from a disease the following will occur?
incidence of disease will decrease
disease rate of TB 2010
prevalence
crude mortality rate in new haven
cumulative incidence
proportion mortality due to TB
cumulative incidence
age sex specific mortality rate
cumulative incidence
cause specific mortalilty
cumulative incidence
advantages and disadvatages of curde mortality
are readily caculated
the numbers are of a whole and do not show a population composition
ad disadvantages of speicific
ad-homogenous sub groups
dis-to many sub groups to calculate
adjusted advant and disadvantage
ad-re moving bias
dont no dis advantage
two measures of association
Relative risk
odds ratio
why analyze data
determine the magniture of association
rule out the role of chance in the results by doing confidence intercal and hypothesis testing
rule out condounfing by restriction or statistical adjustment
properties of RR
Ranges from 0 to infinity (ie cannot be
negative)
If RR = 1 then there is no association
If RR > 1 then there is a positive
association
If RR < 1 then there is negative association
properties of OR
regardless of how the data are
sampled the or will remain the same
it has similar properties to the
RR in terms of range magnitude and statistical significance
under the conditions of rare
disease the odds ratio will be a decent approximation to the true relative risk
difference between observational and experimental design study
lack of exposure manipulation by the researcher in an observational study
observational study
study were nature is allowed to takes its course changes in one chaacteristic are studied in relation to changes in another with out intervention of investigator
goals of epidemiology
maintain an accurate picture of diesase incidnce and prevalence in a population
find and evaluate risk factors and correlates of a disease
prevent futre disease reduce incidnce/prevalence
two types of observational studies
descriptive analytical
analytical studies
ecological-correlational-populations
corss sectional-prevalence-individuals
case control -case reference-individuals
cohort-followup-individuals
experimental studies
another name for it
intervention studies
randomized controlled trials
clinical trials
patients
feild trials
community intervention studies
healthy people
ad vantages og a observatinal study
Subjects more representative of target
population
More practical or feasible (although not
necessarily less expensive)
disadvantages of observational study
Researcher had the least amount of control over
the study
Many distorting biases are possible and mist be
guarded against
basic steps in design study
general hypothesis
operationalize hypothesis
choose study design
choose sample
collect and enter data
analyze data
general hypothesis
conceptual
practical
operationalize hypothesis
§
Define disease
§
Define exposure/correlates of interest
§
Choose a target population
choose study design
§
Based on what is known about a disease
§
Time and money constraints
§
Feasibility of getting an appropriate sample
choose sample
§
Should be representative of target pop
§
Should be large enough to rule out chance
analyze data
§
Calculate observed association between exposure
and disease
§
Rule out the possibility of chance
§
Rule out alternative explanation (confounding)
advantages of cross sectional study
·
Quick
·
Cheep
·
Do not need large sample to do study
·
Unit of study is individual
disadvantages of cross sectional study
·
Samples from cross sectional study designs amy
not be representative of disease in target population
·
The diseases that may be reflected in the sample
group may not be reflected in target population
·
Temporal relationship –idea of chicken an
egg—measuring exposure and disease at same time—run into problem making
cases—one came before other—show/demonstrate—that exposure—risk factor is responsible
for disease—both at same time—no opportunity to show that exposure lead to
disease
advantages of case control
§
Cheep
§
Quick
§
Small population (sample)
§
Establish measures of association using odds
ratio
disadvantages of case control
§
Temororal relationship (which came first)
§
Not always easy to get control
§
Compares prevalence of a disease between exposed
and unexposed groups (aka Prevalence study)
Data collected on individuals in a population or
in a sample of the population about their current disease status and their
pervious exposure status
cross sectional
·
Compare and contrast each design—directional
inquire is present and case control is retrospective
·
What kind of measures of association for case
control—odds ratio –due to its retrospective (it already happened) in a case
control study you cannot get incidence, your going back in time and you already
have those who have the disease—therefore you cannot calculate relative risk
case control study
o
Direction of inquiry is going forward
o
Begins from target population—assemble
(cohort—group of people-specific group—have things in common) cohort(people absolutely without disease)
eliminates confounding
o
Assemble cohort—exposed—non exposed
o
(study)Exposed—disease / no disease (assemble
based on the factor that they have been exposed to risk factor)