Epidemiology Test 1

Front 1

Totality of evidence

Back 1

you can't just use one set of data in order to answer a research question

Front 2

What is an example of EXPOSURE in a study?

Back 2

the effect of EXERCISE on depression.
(exercise= exposure)

Front 3

What is an example of OUTCOME in a study?

Back 3

reduced risk of DEPRESSION
(depression is the outcome)

Front 4

when you design a study what are 4 components that you need?

Back 4

exposure, outcome, comparison group and hypothesis

Front 5

What are the two types of epidemiology studies?

Back 5

experimental and observational

Front 6

What are the key differences between EXPERIMENTAL and OBSERVATIONAL studies?

Back 6

In EXPERIMENTAL, the investigator ONLY OBSERVES the exposures

EXPERIMENTAL: he controls/manipulates the variables

Front 7

What is a RANDOMIZED CONTROL TRIAL?

Back 7

investigator gives cohort exposure and then studies the people (used in experimental)

Front 8

What are some strengths of the RCT study?

Back 8

a) theres a comparison group
b) lots of people therefore only dif. is the exposure!!
b1) and therefore you can control the exposure
c) you can know if one thing caused another (temporal)

Front 9

What are some weaknesses of the RCT?

Back 9

1. expensive
2. ethics
3. you can't just generalize because everyone is different

Front 10

What is a QUASI-EXPERIMENTAL STUDY?

Back 10

(similar to RCT)
1. Nt controlled by investigator

so you look at exposure of people but its not random and its not controlled by the investigator

Front 11

Review: what are the two types of experimental studies?

Back 11

RCT (random, inves. controls exposure)
QUASIexperimental (nt random or controlled by investigator)

Front 12

What are key components of observational studies?

Back 12

1. common
2. natural (we just observe ppl)
3. collect data and analyze
results (its supposed to be like an experimental study)
4. DESCRIPTIVE OR ANALYTIC

Front 13

what are the two types of observational studies?

Back 13

descriptive and analytic

Front 14

what are the components of descriptive studies?

Back 14

1. questions like who what where and why. (who is getting the disease and why are they getting it?)

Front 15

what are the different types of descriptive studies?

Back 15

1. case reports
2. cross sectional
3. corelational

Front 16

what are the components of analytic studies?

Back 16

questions like WHY?

Front 17

what are the different types of analytic studies?

Back 17

1. cohort
2. case control

Front 18

what are descriptive studies used for?

Back 18

1. set up study to then be used in analytic studies
2. DESCRIBE what exists in a POPULATION
3. Uses person, place, or time

Front 19

What is a CASE REPORT? (and what type of study is this?)

Back 19

1. MOST BASIC descriptive study
2. DETAILED report on 1 patient or a few patients
3. ******** LIMITATION: THERE IS NO COMPARISON GROUP
4. can alert people as to the relationship between exposure/outcome relationship

Front 20

what is an example of a case report?

Back 20

OC'S. do they cause liver cancer? maybe, but there is also NO COMPARISON GROUP!

Front 21

What is a cross sectional study?

Back 21

SNAPSHOT.
a. nt based on outcome or exposure status

Front 22

what are some strengths of cross-sectional studies?

Back 22

1. less time
2. no follow up involved

Front 23

what are some limitations of a cross-sectional study?

Back 23

its hard to test your hypothesis because you are not sure if the exposure causes the disease or if the disease causes the exposure (this is called a temporal relationship)

Front 24

what is one way that a cross sectional study could test a hypothesis?

Back 24

if the exposure can't be changed (example: if blue eyes causes depression)

Front 25

ecological or correlational study

Back 25

POPULATIONS!!!!!!!!!
uses data from populations to compare disease frequencies at one time or at dif. times

Front 26

what are some strengths of an ecological study?

Back 26

1. it is quick and inexpensive

Front 27

what are some limitations of an ecological study?

Back 27

1. its from a population nt an individual
2. there are other things at play here
3. these are averages

Front 28

what is an analytical study? and what is its purpose?

Back 28

goal: to determine an exposure outcome w.o using too many resources

Front 29

An analytical study is also used to test a priori hypothesis. What is a priori hypothesis?

Back 29

there are two types:
priori and ad-hoc.

priori: is testing the hypothesis
post hoc: making a hypothesis after you have already done the experiment

Front 30

what is a cohort study?

Back 30

self-selected exposures.
person is free of the outcome but is studied OVER TIME

Front 31

What are the two types of cohort studies?

Back 31

prospective and retrospective
in BOTH:
THE INVESTIGATOR STARTS W. THE EXPOSURE

Front 32

what is a prospective cohort study?

Back 32

only OUT COME FREE INDIVIDUALS WHO ARE AT RISK

limits: can take a long time

Front 33

what is a retrospective study?

Back 33

exposure and outcome occur before the study

Front 34

what are some strengths of a cohort study?

Back 34

1. you can differentiate temporality
2. you don't have recall bias (b/c you are assessing patients before the outcome develops)
3. you can examine lots of outcomes

Front 35

what are some limitations of a cohort study?

Back 35

1. you need lots of people
2. you need a lot of time
3. it is very expensive

Front 36

what is a case control study?

Back 36

1. both exposure and outcome have occurred at the start of the study
2. you don't even know the exposure; you are just assessing the outcome
3. the people w. the outcome come from a large population

heres what you do:
you take a population that has the outcome and ask them what their exposure was.
then you take a population that DOESN'T have the outcome and you ask what the exposure was.

Front 37

what are the strengths of a case control study?

Back 37

1. its good for rare outcomes
2. you can examine lots of exposures
3. better than cohort b/c you can deal w. long induction/latent period.

Front 38

what are the limitations of a case control study?

Back 38

1. more bias
2. you are not sure of the temporal relationship
3. its not so good if the exposure is rare
4. how do you know if you are getting the accurate exposure over the certain time period?

Front 39

how should you choose your study design? what are the factors?

Back 39

1. your question
2. how much you already know
3. frequency of exposure
4. frequency of outcome
5. validity and frequency considerations
6. practical and ethical concerns

Front 40

When should you pick an observational study?

vs.

when should you pick an experimental study?

Back 40

observational: when you want to understand prevention, treatment or etiology
be aware: this is expensive and
not ethical
experimental: when you want to understand treatment, prevention

take note: this is not expensive and it is ethical

Front 41

when should you pick a cohort study?

vs.

when should you pick a case-control study?

Back 41

cohort: when there is a rare exposure and not so much is known about the exposure
2. when you want to evaluate the effects of exposure


when should you pick case-control?
rare outcome
little known about outcome
want to evaluate several exposures
3. long induction, latent period
4. when the data is expensive

Front 42

when should you pick prospective cohort?

when should you pick retrospective?

Back 42

prospective: outcome is short latent period
2. current exposure
3. you want high quality data

retro:

1. long induction
2. historical exposure
3. limited time/resources

Front 43

MEASURES OF DISEASE

Back 43

HOW DO YOU QUANTIFY DISEASE OCCURANCE?

Front 44

what are the factors that quantify occurrence of a disease in a population?

Back 44

1. number of people
2. size of population (This is important!! because if you don't know the size of the population the data is pretty meaningless)
3. length of time that people were followed

Front 45

what are some measures of morbidity? (disease burden)

Back 45

1. incidence
2. prevalence

Front 46

what are the two types of incidence?

Back 46

1. cumulative incidence
2. incidence rate

Front 47

how do you measure prevalence?

Back 47

point and period

Front 48

what are some measures of mortality?

Back 48

1. mortality rates
2. case-fatality
3. proportionate mortality
4. years of life lost.

Front 49

Measures of morbidity:

Back 49

1. number of cases of the disease

Front 50

incidence

Back 50

occurrence of a NEW DISEASE that develops during a specific time

Front 51

prevalence

Back 51

measures frequency of EXISTING disease during a specific time

Front 52

absolute numbers

Back 52

reporting the number of cases (people w. outcome)

this is ...limited? because you don't know the population SIZE but what you can do is compare one year to the next

Front 53

what are the benefits of absolute numbers?

Back 53

1. its easy to do
2. its easy to understand

Front 54

what are the drawbacks of absolute numbers?

Back 54

1. there is no sense of scale
2. its hard to use this information because you don't know if the results are larger than expected or lower than expected (aka, is this good or bad?)

Front 55

when should you use absolute numbers?

Back 55

1. when populations are similar
2. when planning medical resources

Front 56

FORMULA for absolute numbers

Back 56

# of cases in a TIME PERIOD
------------------------------------
population size

Front 57

how do you measure incidence?

Back 57

people who don't have the disease but are AT RISK FOR DEVELOPING THE DISEASE

Front 58

Why is incidence good?

Back 58

1. because you can measure risk - the probability of an event happening

2. you can also measure cumulative incidence (proportion)

or

incidence rate (incidence density)

Front 59

what is cumulative incidence?

Back 59

proportion of people who are disease free who become diseased by the end of a specific time period

Front 60

what is the FORMULA FOR CUMULATIVE INCIDENCE?

Back 60

CI= # new cases during time period
-----------------------------------
total population AT RISK!

Front 61

what are some aspects of cumulative incidence?

Back 61

1. its a proportion
2. estimate the risk of a certain population
3. everyone is followed for a certain time period (it is a closed population

Front 62

what is the INCIDENCE RATE?

Back 62

the rate at which new cases occur in a population that is at risk for the disease

Front 63

What is the FORMULA for in INCIDENCE RATE

Back 63

# of new cases in a specific time
--------------------------------------
total PERSON TIME of observation

Front 64

associations

Back 64

to measure association you have to rule out exposure and disease

Front 65

what do you need in order to be a confounding variable?

Back 65

1. independent cause or predictor of disease
2. associated w. exposure
3. you need to be an intermediate

Front 66

what is a confounding variable?

Back 66

it a variable that explains that exposure and disease are linked through a 3rd factor

Front 67

what is bias?

Back 67

systematic error

Front 68

what are two types of bias?

Back 68

selection bias and observation bias

Front 69

what is selection bias?

Back 69

it is systematic error in the way participants are brought in to the study

Front 70

what is observational bias?

Back 70

systematic error in the way information is obtained once already in the study

Front 71

what is chance?

Back 71

an explanation for the data

Front 72

what can you conclude if p < .05?

Back 72

that it is unlikely that the results are due to chance

Front 73

what about if the confidence interval includes 1?

Back 73

that the results are not significant and you can explain results by saying that they were due to chance

Front 74

how do you move from association to causation?

Back 74

you use totality of evidence

Front 75

what are some criteria that helps you know that something is causal?

Back 75

1. temporality
2. strength of association
3. dose-response
4. replication
5. biology
6. consideration of other things
7. cessation of exposure
8. consistency

Front 76

temporality

Back 76

for an exposure to cause an outcome it has to occur before the outcome occurs

Front 77

strength of relationship

Back 77

the stronger the Relative Risk, the likelier the relationship is to be causal

Front 78

dose response

Back 78

if it is causal, the more you do it the higher the risk

Front 79

replication

Back 79

it should be reported in more than one study

Front 80

biology

Back 80

if there is a biological reason it is more likely to be causal

Front 81

alternative explanations

Back 81

can anything else explain the reason for this?

Front 82

cessation

Back 82

if you stop doing it, the outcome will decrease

Front 83

consistency w. other knowledge

Back 83

what do animal studies show us?

Front 84

how do you find out if something is causal (what is the sequence of events?)

Back 84

1. clinical observations (hypothesis)
2. available data (not ideal)
3. case control
4. cohort
5 RCT