Ch. 3 Epidemiology Flashcards
Define the classic concept of epidemiology
epidemiology derives from the Greek word
epidemic: epi- (among, upon), -demos- (population, people) and –
logos (scientific study)
Whats today’s definition of epidemiology
a science that:
Studies the frequency and distribution of diseases in human
populations.
Determines the causes of diseases.
Characterizes the mechanisms of disease progression.
Determines the factors (biological and social) influencing diseases
What was the beginning of epidemiology?
Hippocrates wrote a treatise called On
Airs, Waters and Places around 400 BC.
- defined Relationships between the living conditions of populations
(diet, fluid intake, exercise) and their health status.
In Spain (XVI century) the term “epidemiology” appears, for the first time...
in a study of a plague
whos involved with
“Germ Theory“ (2)
Louis Pasteur 1860s
Robert Koch 1870s
Who’s involved with miasmic theory of infection?
- The Ancients Greeks: The Origin of the Theory
- The Middle Ages: Corruption of the Air
What is the ancient greeks origin of the theory? (3)
-Hippocrates believed that bad air was the main cause of pestilence.
-Vitruvius: warned of the dangers of various kinds of bad air (exhalations
from marshes, pestilential air, and unhealthy vapors).
-Galen: traced individual susceptibility to the balance of humors in the
body.
What is the middle ages corruption of the air? (@)
-Explanation of plague contagion during the Middle Ages and into the
Renaissance.
-Medieval writers referred to “corruption of the air”, “pestilential air” or
“putrefaction of the air”, NOT “miasma”.
The Chambers 21st Century Dictionary dates the word “miasma” to the
17th century. It is a Latin term derived from the Greek word for ….
pollution
Who popularized the word miasm/miasma? when?
- De noxiis paludum effluviss (Of the poisonous effluvia of malaria), a
work of Giovanni Mari Lancisi
During the germ theory period, ___________ were used to explain many diseases, including tuberculosis,
malaria and cholera.
microorganisms
________ theory was maintained through the middle of the nineteenth century
miasmic
who believed miasma was the main cause of cholera.
Dr. William Farr
Who argued that miasm could not be the cause of cholera?
Charles Earl Johnson
The history of germ theory (just to read while studying)
Microorganisms were used to explain many diseases, including tuberculosis,
malaria and cholera.
Miasmic theory was maintained through the middle of the nineteenth century.
Dr. William Farr believed miasma was the main cause of cholera.
Charles Earl Johnson argued that miasm could not be the cause of this disease.
An influential 1849 essay by British physician John Snow entitled On the
Mode of Communication of Cholera argued that cholera was water-borne. Germ theory was further developed by Louis Pasteur in the 1860s
and Robert Koch in the 1870s.
Who suggested cholera was water borne?
An influential 1849 essay by British physician John Snow entitled On the
Mode of Communication of Cholera argued that cholera was water-borne.
Who further developed germ theory from John Snow?
-louis pasteur & robert koch
What established epidemiology as the science of infectious diseases?
-Advances in the field of microbiology (Pasteur, Koch, etc.)
Scurvy was studied by…?
James lind
What defined the beginning of modern epidemiology ?
(1943): the social aspects
of disease are more important than its causal agent.
The first school of hygiene (public health today) in the world was
created in…
England
What important studies were conducted by the 2nd half of the twentieth century? (2)
- Experimental study on water fluoridation.
- Framingham studied risk factors for cardiovascular disease.
When and where was the cholera epidemic?
London, 1854
_____ described and solved this cholera outbreak 30 years ____ (before/after?) the discovery
of the microorganism causing the
disease (________)
- John Snow
- Before
- Vibrio Cholerae
How did john snow solve the cholera epidemic?
- Quantitative method
- looked at water supply for those affected and noticed the disparity
What is the main goal of epidemiology? (2)
-To achieve the best possible health status in the
community
- Improve the health of the whole population
How does epidemiology differ from clinical medicine? (2)
-It considers the disease as a group phenomenon.
-Is different than in clinical medicine that treats each patient
individually
What are the intermediate objectives of epidemiology? (3)
- diagnosis of the health of a population
- study the origin of the disease progression
- evaluate different health actions
What are the health indicators of a population? (6)
Morbidity and mortality
Demographic indicators (life expectancy, births, deaths …)
Indicators of environmental conditions (water supply, number of
occupants per dwelling …)
Indicators of nutrition (calories and protein consumption per person,
milk consumption in children …)
Indicators of resources and health activities (health expenditure
per capita per year, number of hospital beds, number of doctors per
100,000 inhabitants)
Economic and social indicators (average income per family, literacy
rate, unemployment rate …)
How can we study the origin of disease progression? (3)
Establish probabilities and risks: Predict the likelihood that a person will suffer a disease (risk) with the study of a sample of
individuals that is representative of the general population.
Searching for “causes”.
Identification of new syndromes and clinical manifestations
How can we evaluate different health actions?
Evaluation of diagnostic methods: Economic cost, reliability,
validity, acceptance by the population.
Evaluation of treatments: Efficacy of treatment, administration
mode, acceptance by the population, control of side (unwanted)
effects.
Evaluation of health services
What is the epidemiological method? (5)
- Observing the phenomenon (usually a disease).
What is it?, Who is affected?, When is it?, Where is it? - Counting cases or events. Tabulation (sorting and
ordering) and quantification of the observed data.
To have all the information organized.
To quantify frequency and distribution. - Developing a hypothesis.
It must be “reasonable“; should not be arbitrary and should not be in contradiction
with established facts.
It is an orderly scientific sequence applied to health problems. - Testing the hypothesis.
For ethical reasons, many hypotheses can not be subjected to
experimentation, statistical analysis is used to accept or reject the hypothesis. - Report/conclusions: accept or reject the
hypotheses.
Define descriptive epidemiology (2)
Stop in the first 2 or 3 steps of the epidemiological method:
- observation,
- measurement
- presentation of hypotheses
describes the general characteristics of the distribution of
disease, particularly in relation to person, place and time.
Define analytic epidemiology (2)
- continue to the end of all 5 epidemiological methods
- tests a specific hypothesis about a potential exposure and an outcome of interest. Risk factor-Outcome relationship
Define population
set of all elements
that meet certain properties
where a particular phenomenon
is studied
Define health sciences
a set of individuals in
which you want to study something
What is the population object, goal or reference/target population?
population that you want to study
What is the origin population/study population?
The population that is actually sampled.
-is experimentally accessible and can be measured
When there is no selection bias, what happens ?
-Target population matches study population
Define sample
the part of the population that is going to be studied
What are the different sampling techniques?
1- Convenience sample: volunteers, people who attend a consultation…Does this system have problems?
2- Random sampling: the best procedure to get a representative sample of the population
Define estimation
Attempt to determine the true value of a variable in a
population from the study of a sample.
Estimation involves…
calculating the range that
will include the population value with a certain degree
of confidence.
Define confidence interval
provides a range of values contains the population parameter of interest.
-gives an estimated range of values which is likely to include an unknown
population parameter
the narrower the confidence interval…
the better the precision of the estimation
How can you change the width of the confidence interval? (3)
- Increasing sample size
- Decreasing the measurement error.
- Varying the risk of error you are willing to accept.
What does increasing the sample size do to the width of the confidence interval?
More precision = narrower
But from a certain sample size, to achieve minimal gains in precision, large increases in the sample are needed.
What does Varying the risk of error you are willing to accept do to the width of the confidence interval?
higher confidence interval = bigger range
lower confidence interval = smaller range
define variable
characteristic that is being
measured or observed
What are the types of variables? (2)
- Qualitative/categorical variables
- Quantitative variables
What are the types of qualitative/categorical variables? (3)
- ordinal scales
- nominal/categorical scales
- dichotomous
What are the types of quantitative variables? (2)
- discrete variables
- continuous variables
What is a qualitative / categorical variable? (2)
-are those that
are described in terms of presence or absence of an attribute
-If you cannot add it…it’s qualitative
What is a quantitative variable?
measured on a
numeric or quantitative scale
What is an ordinal scale? (2)
- qualitative variable
- rank amongst the categories within a range
ex. staging of tumors, socioeconomic status, “Strongly agree, agree, neutral, disagree, etc”
What is nominal/categorical scale? (2)
- qualitative variables
- categories cannot be ordered
ex. gender, blood group, presence/abscence of disease, symptom, risk factor
What is dichotomous scale? (2)
- qualitative variables
- can only take 2 values
ex. can be ordinal (rich vs poor) or nominal (gender)
What is a discrete variable? (3)
- quantitative variable
- can only be an integer
- result of counting process
ex. # of hospital admissions, # of children
What is a continuous variable? (3)
- quantitative variable
- any numerical value with decimals
- result of a measure
ex. weight, height, blood cholesterol
What is a dependent variable?
variable being affected by independent variable
What is an independent variable?
a variable that does not depend on that of another
What type of variables are measured in epidemioloigal studies? (person) (7)
- age
- gender
- social class
- occupation
- ethnicity
- religion
- marital status
What variables are always collected /measured in all epdemiological studies? (4)
Age
gender
location
time (of study and duration of schedule - ex. for seasonal flu)
