Design 1 Health and disease are not distributed haphazardly in a population Big Epi Idea Health and disease are not distributed haphazardly in a population There are patterns to their occurrence ID: 930947
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Slide1
Day 1 Study DesignsCross-Sectional Design
1
Slide2Health and disease are not distributed haphazardly in a population.Big Epi Idea
Slide3Health and disease are not distributed haphazardly in a population. There are patterns to their occurrence.Big Epi Idea
Slide4Health and disease are not distributed haphazardly in a population. There are patterns to their occurrence. These patterns can be identified through the surveillance of populations.Big Epi Idea
Slide5Health and disease are not distributed haphazardly in a population. There are patterns to their occurrence. These patterns can be identified through the surveillance of populations. Examining these patterns of health and disease can help formulate hypotheses about their possible causes. Big Epi Idea
Slide66
Slide77
A particular or detached incident or fact of an interesting nature; a biographical incident or fragment; a single passage of private life.
Anecdote
Study Designs
Slide88
Anecdote
Science
Transforming Anecdote to Science
Study Designs
A particular or detached incident or fact of an interesting nature; a biographical incident or fragment;
a
single passage of private life.
Slide99
Anecdote
Science
DZ
Transforming Anecdote to Science
Study Designs
A particular or detached incident or fact of an interesting nature; a biographical incident or fragment;
a
single passage of private life.
Slide1010
Anecdote
Science
Transforming Anecdote to Science
Study Designs
A particular or detached incident or fact of an interesting nature; a biographical incident or fragment;
a
single passage of private life.
Slide1111
Anecdote
Science
Transforming Anecdote to Science
Study Designs
A particular or detached incident or fact of an interesting nature; a biographical incident or fragment;
a
single passage of private life.
Slide1212
Transforming Anecdote to Science
Study Designs
Slide1313
Absolutely nothing in the available arsenal of anti-emetics worked at all.
I
was miserable and came to dread the frequent treatments
with
an almost perverse intensity
.
I
had heard that marijuana often worked well against nausea.
I
was reluctant to try it because I had never smoked any substance habitually (and didn’t even know how to inhale).
Moreover
, I had tried marijuana twice (in the 1960s) … and had hated it ….
Marijuana
worked like a charm …. The
sheer bliss of not experiencing nausea -
and
not having to fear it for all the days intervening between treatments - was the greatest boost I received in all my year of treatment,
and
surely the most important effect upon my eventual cure.
Transforming Anecdote to Science
Study Designs
Slide1414
Anecdote
Science
Transforming Anecdote to Science
Study Designs
A particular or detached incident or fact of an interesting nature; a biographical incident or fragment;
a
single passage of private life.
Slide15Slide16Exposure (E)
Outcome (O)
Time
4 Basic Epidemiological Study Designs
Slide1717
4 Basic Epidemiological Study Designs
Slide184 Basic Epidemiological Study Designs
Slide19Exposure (E)
Outcome (O)
Sample
Time
Randomly Assigned
E
E
O
O
O
O
Randomized Controlled Trial
Slide20Exposure (E)
Outcome (O)
Sample
Time
Randomly Assigned
E
E
O
O
O
O
Cohort Study
Cohort
Slide21Exposure (E)
Outcome (O)
Time
O
O
E
E
E
E
Case-Control Study
Slide22Exposure (E)
Outcome (O)
Time
E
E
O
O
Cross-Sectional Study
Slide2323
Anecdote
Science
Transforming Anecdote to Science
Study Designs
A particular or detached incident or fact of an interesting nature; a biographical incident or fragment;
a
single passage of private life.
Slide24Slide2525
4 Basic Epidemiological Study Designs
LA
NY
Slide2626
An epidemiologic
study
in which subjects are assigned
to
groups to receive or not receive a hypothesized beneficial intervention.
Randomized Controlled Trial
Slide2727
4 Basic Epidemiological Study Designs
LA
NY
Coffee Consumption and Sleep Duration
Slide28Just as in the controlled trial, the epidemiologist is also on the train during the entire journey. But there is an important difference. The epidemiologist is not telling passengers what to do. Rather, the epidemiologist is just observing them and counting. Passengers are not being told to have or not have an exposure, they are just living their normal lives. The epidemiologist, on the ride for the whole journey, just keeps observing everyone’s exposures and whether or not they develop the outcome during the journey.
4 Basic Epidemiological Study Designs
Slide2929
4 Basic Epidemiological Study Designs
LA
NY
Coffee Consumption and Sleep Duration
Slide30The epidemiologist is not on the journey. Rather, the epidemiologist is waiting at the train station at the end of the journey. As passengers get off the train, the epidemiologist selects a group of passengers with the outcome and a similar
group of passengers
without
the
outcome. The epidemiologist then asks each person in each group questions about their exposures during the train ride. The epidemiologist relies on passengers’ memories of their exposures that occurred during the trip.
4 Basic Epidemiological Study Designs
Slide3131
4 Basic Epidemiological Study Designs
LA
NY
Coffee Consumption and Sleep Duration
Slide32The epidemiologist, who has not been on the journey, stops the train somewhere during the trip (kind of like a train robbery) and takes a “snapshot” of all the passengers by asking them whether or not they have the exposure and whether or not they have the outcome. Then the epidemiologist leaves the train and goes home to analyze the data from that particular day. The journey continues without the epidemiologist.
4 Basic Epidemiological Study Designs
Slide3333
4 Basic Epidemiological Study Designs
LA
NY
Coffee Consumption and Sleep Duration
Slide3434
Slide3535
4 Basic Epidemiological Study Designs
Coffee Consumption and Sleep Duration
Photography
Slide3636
4 Basic Epidemiological Study Designs
RECORD
Coffee Consumption and Sleep Duration
Photography
Slide3737
4 Basic Epidemiological Study Designs
Coffee Consumption and Sleep Duration
Photography
Slide3838
4 Basic Epidemiological Study Designs
Coffee Consumption and Sleep Duration
Photography
Slide3939
Slide4040
Strengths
Randomized Controlled Trial
R
andomization distributes possible confounders equally in exposed and unexposed
Easier to
blind / mask
than observational
studies
Slide4141
Randomized Controlled Trial
Expensive
in terms of time and money
Volunteer biases:
participates
may not be representative of the
population
Loss to follow-up attributed
to
treatment / exposure
Limitations
Slide4242
Cohort Study
Subjects
in cohorts can be matched, which limits the influence of confounding variables
Easier
and cheaper than a randomized controlled
trial
Can establish time order of exposure and outcome
Strengths
Slide4343
Cohort Study
No
randomization, which means that imbalances in
participant
characteristics could exist
Outcome
of interest could take time to occur
Loss to
follow-up
Limitations
Slide4444
Case-Control Study
Good
for studying rare
outcomes
Less time needed to conduct the study because the
outcome
has already occurred
Lets you simultaneously look at multiple
exposures
Useful as initial studies to establish an association
Strengths
Slide4545
Case-Control Study
P
roblems
with data quality because
of reliance on memory
People
with a condition will be more motivated to recall
exposures
(also called recall bias
)
It
can be difficult to find a suitable control
group
Inability to determine with certainty the time order of the exposure and the outcome
Limitations
Slide4646
Cross-Sectional Study
Relatively
quick and easy to conduct (no long periods of follow-up
)
Data on all variables
are
only collected
once
Able to measure prevalence for all factors under
investigation
Multiple outcomes and exposures can be
studied
Strengths
Slide4747
Cross-Sectional Study
Difficult
to determine whether the outcome followed exposure in time or exposure resulted from the outcome.
Not suitable for studying rare
outcomes
or
outcomes
with a short duration.
As cross-sectional studies measure prevalent rather than incident cases, the data will always reflect determinants of survival as well as
etiology.
Susceptible
to bias due to low response and misclassification due to recall bias
.
Limitations
Slide4848
Slide4949
Randomized Controlled Trial
Typical Measure of Effect
(A way of quantifying the extent to which an exposure and an outcome are associated)
Relative Risk or Risk Ratio
Slide5050
Cohort Study
Typical Measure of Effect
(A way of quantifying the extent to which an exposure and an outcome are associated)
Relative Risk or Risk Ratio
Slide5151
Case-Control Study
Typical Measure of Effect
(A way of quantifying the extent to which an exposure and an outcome are associated)
Odds Ratio or Relative Odds
Slide5252
Cross-Sectional Study
Typical Measure of Effect
(A way of quantifying the extent to which an exposure and an outcome are associated)
Prevalence Ratio
Slide53Slide5454
4 Basic Epidemiological Study Designs
Slide5555
4 Basic Epidemiological Study Designs
The goal of every epidemiological study is to harvest valid and precise information about the relationship between an exposure and a disease in a population.
The various study designs merely represent different ways of harvesting this information.
Essentials in Epidemiology in Public Health
Ann
Aschengrau
and George R.
Seage
III
Slide5656
4 Basic Epidemiological Study Designs
The goal of every epidemiological study is to harvest valid and precise information about the relationship between an exposure and an outcome in a population.
The various study designs merely represent different ways of harvesting this information.
Essentials in Epidemiology in Public Health
Ann
Aschengrau
and George R.
Seage
III
Slide57Slide58A hypothesis can be tested by comparing the frequency of disease in selected groups of people with and without an exposure to determine if the exposure and the disease are associated.Big Epi Idea
Slide59A hypothesis can be tested by comparing the frequency of disease in selected groups of people with and without an exposure to determine if the exposure and the disease are associated. When an exposure is hypothesized to have a beneficial effect, studies can be designed in which a group of people is intentionally exposed to the hypothesized cause and compared to a group that is not exposed.
Big Epi Idea
Slide60A hypothesis can be tested by comparing the frequency of disease in selected groups of people with and without an exposure to determine if the exposure and the disease are associated. When an exposure is hypothesized to have a beneficial effect, studies can be designed in which a group of people is intentionally exposed to the hypothesized cause and compared to a group that is not exposed. When an exposure is hypothesized to have a detrimental effect, it is not ethical to intentionally expose a group of people.
Big Epi Idea
Slide61A hypothesis can be tested by comparing the frequency of disease in selected groups of people with and without an exposure to determine if the exposure and the disease are associated. When an exposure is hypothesized to have a beneficial effect, studies can be designed in which a group of people is intentionally exposed to the hypothesized cause and compared to a group that is not exposed. When an exposure is hypothesized to have a detrimental effect, it is not ethical to intentionally expose a group of people. In these circumstances, studies can be designed that observe groups of free-living people with and without the exposure.
Big Epi Idea
Slide6262
Slide63Epi Team Challenge
X-Sectional Study
Randomized Controlled Trial
Case-Control Study
Cohort Study
What’s My Design?
Slide64Epidemiologist is involved during the entire time from exposure to outcome.
Assign participants to treatment and control groups.
Follow through time and compare risk of the outcome in treatment group with risk of the outcome in control group.
Give exposure to treatment group, but not control group.
RCT
What’s My Design?
Guided Practice
Slide65Epidemiologist is involved during the entire time from exposure to outcome.
Select a healthy study sample.
Follow through time and compare risk of the outcome in exposed group to risk of the outcome in unexposed group.
Observe who has and has not been exposed.
Cohort Study
What’s My Design?
Guided Practice
Slide66Epidemiologist is involved after the outcome has occurred and relies on subjects’ memories to gather information about exposure.
Select a group of people with the outcome and a similar group of people without
the
outcome.
Compare the odds of exposed people in the two groups.
Ask both groups about their exposures in the past.
Case-Control Study
What’s My Design?
Guided Practice
Slide67Ask each person about both exposure and outcome at one point in time.
Prevalence of outcome in exposed group is compared to prevalence
of outcome
in unexposed group.
Select a study sample.
Cross-Sectional Study
What’s My Design?
Guided Practice
Slide68Slide69Sample
E
E
O
O
O
O
Cohort Study
What’s My Design?
Slide704 Basic Epidemiological Study Designs
Slide71The epidemiologist, who has not been on the journey, stops the train somewhere during the trip (kind of like a train robbery) and takes a “snapshot” of all the passengers by asking them whether or not they have the exposure and whether or not they have the outcome. Then the epidemiologist leaves the train and goes home to analyze the data from that particular day. The journey continues without the epidemiologist.
Cross-Sectional Study
What’s My Design?
Slide724 Basic Epidemiological Study Designs
Slide73O
O
E
E
E
E
Case-Control Study
What’s My Design?
Slide744 Basic Epidemiological Study Designs
Slide75Sample
Randomly Assigned
E
E
O
O
O
O
RCT
What’s My Design?
Slide764 Basic Epidemiological Study Designs
Slide77RECORD
Cohort Study
What’s My Design?
Slide784 Basic Epidemiological Study Designs
Slide79E
E
O
O
Cross-Sectional Study
What’s My Design?
Slide804 Basic Epidemiological Study Designs
Slide81Randomly Assigned
RCT
What’s My Design?
Slide824 Basic Epidemiological Study Designs
Slide83Cross-Sectional Study
What’s My Design?
Slide844 Basic Epidemiological Study Designs
Slide85Sample
Randomly Assigned
E
E
RCT
What’s My Design?
Slide864 Basic Epidemiological Study Designs
Slide87RCT
What’s My Design?
Slide884 Basic Epidemiological Study Designs
Slide89Just as in the controlled trial, the epidemiologist is also on the train during the entire journey. But there is an important difference. The epidemiologist is not telling passengers what to do. Rather, the epidemiologist is just observing them and counting. Passengers are not being told to have or not have an exposure, they are just living their normal lives. The epidemiologist, on the ride for the whole journey, just keeps observing everyone’s exposures and whether or not they develop the outcome during the journey.
Cohort Study
What’s My Design?
Slide904 Basic Epidemiological Study Designs
Slide91E
E
O
O
Cross-Sectional Study
What’s My Design?
Slide924 Basic Epidemiological Study Designs
Slide93E
E
E
E
Case-Control Study
What’s My Design?
Slide944 Basic Epidemiological Study Designs
Slide95The epidemiologist is not on the journey. Rather, the epidemiologist is waiting at the train station at the end of the journey. As passengers get off the train, the epidemiologist selects a group of passengers with the outcome and a similar
group of passengers
without
the
outcome. The epidemiologist then asks each person in each group questions about their exposures during the train ride. The epidemiologist relies on passengers’ memories of their exposures that occurred during the trip.
Case-Control Study
What’s My Design?
Slide964 Basic Epidemiological Study Designs
Slide97Sample
Randomly Assigned
RCT
What’s My Design?
Slide984 Basic Epidemiological Study Designs
Slide99Sample
E
E
O
O
O
O
Cohort Study
What’s My Design?
Slide1004 Basic Epidemiological Study Designs
Slide101E
E
E
E
Case-Control Study
What’s My Design?
Slide1024 Basic Epidemiological Study Designs
Slide1034 Basic Epidemiological Study Designs
Slide104O
O
O
O
RCT and Cohort Study
What’s My Design?
Slide1054 Basic Epidemiological Study Designs
Slide106Sample
RCT and Cohort Study
What’s My Design?
Slide1074 Basic Epidemiological Study Designs
Slide108Case-Control Study
What’s My Design?
Slide1094 Basic Epidemiological Study Designs
Slide110Case-Control Study
What’s My Design?
Slide1114 Basic Epidemiological Study Designs
Slide112O
O
O
O
RCT and Cohort Study
What’s My Design?
Slide1134 Basic Epidemiological Study Designs
Slide114What’s My Design?
RCT and Cohort Study
Slide1154 Basic Epidemiological Study Designs
Slide116E
E
O
O
Cross-Sectional Study
What’s My Design?
Slide1174 Basic Epidemiological Study Designs
Slide118O
O
E
E
E
E
Case-Control Study
What’s My Design?
Slide1194 Basic Epidemiological Study Designs
Slide120Sample
Randomly Assigned
E
E
O
O
O
O
RCT
What’s My Design?
Slide1214 Basic Epidemiological Study Designs
Slide122Epidemiologist is involved during the entire time from exposure to outcome.
Select a healthy study sample.
Follow through time and compare risk of the outcome in exposed group to risk of the outcome in unexposed group.
Observe who has and has not been exposed.
Cohort Study
What’s My Design?
Slide1234 Basic Epidemiological Study Designs
Slide124Epidemiologist is involved after the outcome has occurred and relies on subjects’ memories to gather information about exposure.
Select a group of people with the outcome and a similar group of people without
the
outcome.
Compare the odds of exposed people in the two groups.
Ask both groups about their exposures in the past.
Case-Control Study
What’s My Design?
Slide1254 Basic Epidemiological Study Designs
Slide126Epidemiologist is involved during the entire time from exposure to outcome.
Assign participants to treatment and control groups.
Follow through time and compare risk of the outcome in treatment group with risk of the outcome in control group.
Give exposure to treatment group, but not control group.
RCT
What’s My Design?
Slide1274 Basic Epidemiological Study Designs
Slide128Ask each person about both exposure and outcome at one point in time.
Prevalence of outcome in exposed group is compared to prevalence
of outcome
in unexposed group.
Select a study sample.
Cross-Sectional Study
What’s My Design?
Slide1294 Basic Epidemiological Study Designs
Slide1304 Basic Epidemiological Study Designs
The goal of every epidemiological study is to harvest valid and precise information about the relationship between an exposure and an outcome in a population.
The various study designs merely represent different ways of harvesting this information.
Essentials in Epidemiology in Public Health
Ann
Aschengrau
and George R.
Seage
III
Slide131Slide132Epi Team Challenge
X-Sectional Study
Randomized Controlled Trial
Case-Control Study
Cohort Study
Which Design Is Best?
Slide133Study DesignsStrengthsLimitationsRCTCohort
Study
Case-Control Study
Cross-Sectional Study
Which Study Design Is Best?
Slide134Study DesignsStrengthsLimitationsRCTCohort
Study
Case-Control Study
Cross-Sectional Study
Which study design is the fastest?
Which Study Design Is Best?
Slide135Which Study Design Is Best?
Slide136Study DesignsStrengthsLimitationsRCT
Cohort
Study
Case-Control Study
Cross-Sectional Study
Fastest
Which study design is the fastest?
Which Study Design Is Best?
Slide137Study DesignsStrengthsLimitationsRCTCohort
Study
Case-Control Study
Cross-Sectional Study
Fastest
Which study design
s
are the most time consuming?
Which Study Design Is Best?
Slide138Which Study Design Is Best?
Slide139Study DesignsStrengthsLimitationsRCT
Time Consuming
Cohort
Study
Time Consuming
Case-Control Study
Cross-Sectional Study
Fastest
Which study design
s
are the most time consuming?
Which Study Design Is Best?
Slide140Study DesignsStrengthsLimitationsRCTTime Consuming
Cohort
Study
Time Consuming
Case-Control Study
Cross-Sectional Study
Fastest
Which study design is the most scientifically sound?
Which Study Design Is Best?
Slide141Which Study Design Is Best?
Slide142Study DesignsStrengthsLimitationsRCTMost Scientifically Sound
Time Consuming
Cohort
Study
Time Consuming
Case-Control Study
Cross-Sectional Study
Fastest
Which study design is the most scientifically sound?
Which Study Design Is Best?
Slide143Study DesignsStrengthsLimitationsRCTMost Scientifically SoundTime Consuming
Cohort
Study
Time Consuming
Case-Control Study
Cross-Sectional Study
Fastest
Which study design is best for studying rare outcomes?
Which Study Design Is Best?
Slide144Which Study Design Is Best?
Slide145Study DesignsStrengthsLimitationsRCTMost Scientifically Sound
Time Consuming
Cohort
Study
Time Consuming
Case-Control Study
Can Study Rare Outcomes
Cross-Sectional Study
Fastest
Which study design is best for studying rare outcomes?
Which Study Design Is Best?
Slide146Study DesignsStrengthsLimitationsRCTMost Scientifically SoundTime Consuming
Cohort
Study
Time Consuming
Case-Control Study
Can Study Rare Outcomes
Cross-Sectional Study
Fastest
Which study design
s
do not identify the time order of the exposure and the outcome?
Which Study Design Is Best?
Slide147Which Study Design Is Best?
Slide148Study DesignsStrengthsLimitationsRCTMost Scientifically Sound
Time Consuming
Cohort
Study
Time Consuming
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion
Cross-Sectional Study
Fastest
Possible Time-Order Confusion
Which Study Design Is Best?
Which study design
s
do not identify the time order of the exposure and the outcome?
Slide149Study DesignsStrengthsLimitationsRCTMost Scientifically SoundTime Consuming
Cohort
Study
Time Consuming
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion
Cross-Sectional Study
Fastest
Possible Time-Order Confusion
With which study design are you least certain of your results?
Which Study Design Is Best?
Slide150Which Study Design Is Best?
Slide151Study DesignsStrengthsLimitationsRCTMost Scientifically Sound
Time Consuming
Cohort
Study
Time Consuming
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion
Cross-Sectional Study
Fastest
Possible Time-Order Confusion
Least Certain of Results
With which study design are you least certain of your results?
Which Study Design Is Best?
Slide152Study DesignsStrengthsLimitationsRCTMost Scientifically SoundTime Consuming
Cohort
Study
Time Consuming
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion
Cross-Sectional Study
Fastest
Possible Time-Order Confusion
Least Certain of Results
Which study design provides the best measure of exposure?
Which Study Design Is Best?
Slide153Which Study Design Is Best?
Slide154Study DesignsStrengthsLimitationsRCTMost Scientifically SoundBest Measure of Exposure
Time Consuming
Cohort
Study
Time Consuming
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion
Cross-Sectional Study
Fastest
Possible Time-Order Confusion
Least Certain of Results
Which study design provides the best measure of exposure?
Which Study Design Is Best?
Slide155Study DesignsStrengthsLimitationsRCTMost Scientifically SoundBest Measure of Exposure
Time Consuming
Cohort
Study
Time Consuming
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion
Cross-Sectional Study
Fastest
Possible Time-Order Confusion
Least Certain of Results
Which study design is the most accurate observational study?
Which Study Design Is Best?
Slide156Which Study Design Is Best?
Slide157Study DesignsStrengthsLimitationsRCTMost Scientifically SoundBest Measure of Exposure
Time Consuming
Cohort
Study
Most Accurate Observational Study
Time Consuming
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion
Cross-Sectional Study
Fastest
Possible Time-Order Confusion
Least Certain of Results
Which study design is the most accurate observational study?
Which Study Design Is Best?
Slide158Study DesignsStrengthsLimitationsRCTMost Scientifically SoundBest Measure of Exposure
Time Consuming
Cohort
Study
Most Accurate Observational Study
Time Consuming
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion
Cross-Sectional Study
Fastest
Possible Time-Order Confusion
Least Certain of Results
Which study design is the least expensive?
Which Study Design Is Best?
Slide159Which Study Design Is Best?
Slide160Study DesignsStrengthsLimitationsRCTMost Scientifically SoundBest Measure of Exposure
Time Consuming
Cohort
Study
Most Accurate Observational Study
Time Consuming
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion
Cross-Sectional Study
Fastest
Least Expensive
Possible Time-Order ConfusionLeast Certain of Results
Which study design is the least expensive?
Which Study Design Is Best?
Slide161Study DesignsStrengthsLimitationsRCTMost Scientifically SoundBest Measure of Exposure
Time Consuming
Cohort
Study
Most Accurate Observational Study
Time Consuming
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion
Cross-Sectional Study
Fastest
Least Expensive
Possible Time-Order ConfusionLeast Certain of Results
Which study design
s are the most expensive?
Which Study Design Is Best?
Slide162Which Study Design Is Best?
Slide163Study DesignsStrengthsLimitationsRCTMost Scientifically SoundBest Measure of Exposure
Time Consuming
Most Expensive
Cohort
Study
Most Accurate Observational Study
Time Consuming
Most Expensive
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion
Cross-Sectional Study
FastestLeast ExpensivePossible Time-Order Confusion
Least Certain of Results
Which study designs are the most expensive?
Which Study Design Is Best?
Slide164Study DesignsStrengthsLimitationsRCTMost Scientifically SoundBest Measure of Exposure
Time Consuming
Most Expensive
Cohort
Study
Most Accurate Observational Study
Time Consuming
Most Expensive
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion
Cross-Sectional Study
FastestLeast ExpensivePossible Time-Order ConfusionLeast Certain of Results
Which study design would be unethical for harmful exposures?
Which Study Design Is Best?
Slide165Which Study Design Is Best?
Slide166Study DesignsStrengthsLimitationsRCTMost Scientifically SoundBest Measure of Exposure
Time Consuming
Most Expensive
Unethical for Harmful Exposures
Cohort
Study
Most Accurate Observational Study
Time Consuming
Most Expensive
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion
Cross-Sectional StudyFastestLeast Expensive
Possible Time-Order ConfusionLeast Certain of Results
Which study design would be unethical for harmful exposures?
Which Study Design Is Best?
Slide167Study DesignsStrengthsLimitationsRCTMost Scientifically SoundBest Measure of Exposure
Time Consuming
Most Expensive
Unethical for Harmful Exposures
Cohort
Study
Most Accurate Observational Study
Time Consuming
Most Expensive
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion
Cross-Sectional StudyFastestLeast Expensive
Possible Time-Order ConfusionLeast Certain of Results
Which study designs
create the possibility of error in recalling past exposures?
Which Study Design Is Best?
Slide168Which Study Design Is Best?
Slide169Study DesignsStrengthsLimitationsRCTMost Scientifically SoundBest Measure of Exposure
Time Consuming
Most Expensive
Unethical for Harmful Exposures
Cohort
Study
Most Accurate Observational Study
Time Consuming
Most Expensive
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion
Possible Error in Recalling ExposuresCross-Sectional StudyFastestLeast Expensive
Possible Time-Order ConfusionLeast Certain of Results Possible Error in Recalling Exposures
Which study design
s
create the possibility of error in recalling past exposures?
Which Study Design Is Best?
Slide170Which Study Design Is Best?
Which study design is best?
It depends ….
Slide171Study DesignsStrengthsLimitationsRCTMost Scientifically SoundBest Measure of Exposure
Time Consuming
Most Expensive
Unethical for Harmful Exposures
Cohort
Study
Most Accurate Observational Study
Time Consuming
Most Expensive
Case-Control Study
Can Study Rare Outcomes
Possible Time-Order Confusion Possible Error in Recalling Exposures
Cross-Sectional StudyFastestLeast Expensive
Possible Time-Order ConfusionLeast Certain of Results Possible Error in Recalling Exposures
Which study design is best?
Which Study Design Is Best?
It depends ….
Slide172Which Study Design Is Best?
It depends ….
Whether the exposure is believed to be beneficial
Time urgency
How much is known about the association
Money
Regulations
Slide173Which Design Is Best?
Study Designs
Strengths
Limitations
RCT
Most Scientifically Sound
Best Measure of Exposure
Time Consuming
Unethical for Harmful Exposures
Most Expensive
Cohort
Study
Most Accurate Observational StudyGood Measure of ExposureTime ConsumingMost Expensive
Case-Control StudyCan Study Rare Outcomes
Possible Time-Order ConfusionPossible Error in Recalling ExposuresCross-Sectional StudyFastestLeast ExpensivePossible Time-Order ConfusionPossible Error in Recalling Exposures
It depends ….
Slide174174
4 Basic Epidemiological Study Designs
The goal of every epidemiological study is to harvest valid and precise information about the relationship between an exposure and an outcome in a population.
The various study designs merely represent different ways of harvesting this information.
Essentials in Epidemiology in Public Health
Ann
Aschengrau
and George R.
Seage
III
Slide175175
Slide176Cross-Sectional Design
176
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4 Basic Epidemiological Study Designs
Slide178178
A study in which exposure and outcome are measured simultaneously in a given population or a sample of that population.
This study can be thought of as providing a "snapshot" of the frequency of an exposure and outcome at a particular point in time.
Data that are collected as part of a cross-sectional study can be used to assess the prevalence of an outcome.
Also called a prevalence study.
Cross-Sectional Study
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An observational study in which the presence or absence of an outcome and the presence or absence of a hypothesized cause of that outcome are identified in a population at one particular time.
Cross-Sectional Study
Slide180Cross-sectional studies are carried out at one time point or over a short period.
Cross-Sectional Study
Slide181Cross-sectional studies are carried out at one time point or over a short period. They are usually conducted to estimate the prevalence of the outcome of interest for a given population, commonly for the purposes of public health planning.
Cross-Sectional Study
Slide182Cross-sectional studies are carried out at one time point or over a short period. They are usually conducted to estimate the prevalence of the outcome of interest for a given population, commonly for the purposes of public health planning. Data can also be collected on individual characteristics, including exposure to risk factors, alongside information about the outcome.
Cross-Sectional Study
Slide183Cross-sectional studies are carried out at one time point or over a short period. They are usually conducted to estimate the prevalence of the outcome of interest for a given population, commonly for the purposes of public health planning. Data can also be collected on individual characteristics, including exposure to risk factors, alongside information about the outcome. In this way cross-sectional studies provide a 'snapshot' of the outcome and the characteristics associated with it, at a specific point in time.
Cross-Sectional Study
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Cross-Sectional Study
Difficult
to determine whether the outcome followed exposure in time or exposure resulted from the outcome.
Not suitable for studying rare
outcomes
or
outcomes
with a short duration.
As cross-sectional studies measure prevalent rather than incident cases, the data will always reflect determinants of survival as well as
etiology.
Susceptible
to bias due to low response and misclassification due to recall bias
.
Limitations
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Cross-Sectional Study
Relatively
quick and easy to conduct (no long periods of follow-up
)
Data on all variables
are
only collected
once
Able to measure prevalence for all factors under
investigation
Multiple outcomes and exposures can be
studied
Strengths
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Cross-Sectional Study
Typical Measure of Effect
(A way of quantifying the extent to which an exposure and an outcome are associated)
Prevalence Ratio
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4 Basic Epidemiological Study Designs
Slide190Slide191A hypothesis can be tested by comparing the frequency of disease in selected groups of people with and without an exposure to determine if the exposure and the disease are associated.Big Epi Idea
Slide192A hypothesis can be tested by comparing the frequency of disease in selected groups of people with and without an exposure to determine if the exposure and the disease are associated. When an exposure is hypothesized to have a beneficial effect, studies can be designed in which a group of people is intentionally exposed to the hypothesized cause and compared to a group that is not exposed.
Big Epi Idea
Slide193A hypothesis can be tested by comparing the frequency of disease in selected groups of people with and without an exposure to determine if the exposure and the disease are associated. When an exposure is hypothesized to have a beneficial effect, studies can be designed in which a group of people is intentionally exposed to the hypothesized cause and compared to a group that is not exposed. When an exposure is hypothesized to have a detrimental effect, it is not ethical to intentionally expose a group of people.
Big Epi Idea
Slide194A hypothesis can be tested by comparing the frequency of disease in selected groups of people with and without an exposure to determine if the exposure and the disease are associated. When an exposure is hypothesized to have a beneficial effect, studies can be designed in which a group of people is intentionally exposed to the hypothesized cause and compared to a group that is not exposed. When an exposure is hypothesized to have a detrimental effect, it is not ethical to intentionally expose a group of people. In these circumstances, studies can be designed that observe groups of free-living people with and without the exposure.
Big Epi Idea
Slide195EPI CHALLENGEProposal FormCross-Sectional Study Design4a. Describe how your hypothesis can be tested in your high school using the cross-sectional design. Include a diagram of the study design. 4b. Describe the advantages of using a cross-sectional study.
4c. Describe two or more challenges your team will face while testing this hypothesis in your school.
Slide1964 Basic Epidemiological Study Designs
Handout