Centers for Disease Control and PreventionGlobal Health Odyssey Museum
Tom Harkin Global Communications Center June 8-12, 2009
Teach EpidemiologyProfessional Development Workshop
Day5
WendyNot Observed
Empty Beer Bottles
MarkCause
Scenario 1- Guilt By Association
Association Cause
XObserved
Confounding
Definition
A situation in which an association between a given exposure
and an outcome is observed as a result of the influence of a third unobserved factor, called a confounder.
Confounding
Review
A situation in which an association between a given exposure (Mark) and an outcome (empty bottles) is observed as a
result of the influence of a third unobserved factor, called a confounder (Wendy)
Obviously we should have spoken to Wendy.
Cause
Association Cause
XObserved
Not Observed Confounder
Match-Carrying
Lung Cancer
Review - Diagram of Confounding
Smoking
Confounding 2
Cause
Association Cause
XObserved
Not Observed Confounder
Drinking Alcohol during Pregnancy
Low Birth Weight
Babies
Confounding 3
Cause
Association Cause
XObserved
Not Observed Confounder
Eating Pretzels
Auto Accidents
Confounding 5
Cause
Association Cause
XObserved
Not Observed Confounder
Playing Volleyball
Skin Cancer
Confounding 6
Cause
Association Cause
XObserved
Not Observed Confounder
Driving Motorcycles
Hepatitis C
Confounding 7
Cause
Association Cause
XObserved
Not Observed Confounder
Playing Baseball
Oral Cancer
Died Not Died
Scenario
Had Bedsores
No Bedsores 90
b
d
a
c
Risks Relative Risk
79
286
745
8,290
824
8,576
9%
3%
Total
X 3
Individuals with bedsores are 3 times more likely to die than those without bedsores.
DeathGetting
bedsores
“The study establishes a clear
progression beginning with
patients getting bed sores and ending
with death.”
“If we can keep our patients from
getting bedsores, then we can go a long way towards
preventing hospital deaths.”
Cause
Scenario 2
Confounding
Is cause the only possible
association between the
two?
1. Cause
2. Chance
3. Bias
Reverse Time Order
4.
5. Confounding
Scenarios
?
Not Observed
DeathBedsoresCause
Association Cause
XObserved
Wendy
Not Observed
Broken Beer Bottles
MarkCause
Association Cause
XObserved
Scenario 1 Scenario 2
Scenario 2
?
DeathBedsoresCause
Association Cause
XObserved
Severity of Medical
Condition
Not Observed Brainstorm
Stratification
Definition
A procedure which creates strata based on categories of the suspected confounding variable and examines the exposure-disease association within each stratum (subgroups).
Died Not Died
Scenario 2 Stratified
Had Bedsores
No Bedsores 90
b
d
a
c
Risks Relative Risk
55
5
51
5
106
19
51.9%
50.0%
Total
Patients with
High Medical Severity
x1
There is no association!!
Died Not Died
Scenario 2 Stratified
Had Bedsores
No Bedsores 90
b
d
a
c
Risks Relative Risk
24
281
694
8,285
718
8,566
3.3%
3.3%
Total
Patients with
Low Medical Severity
There is no association!!
x1
Died Not Died
Scenario 2 Adjusted
High Severity
Low Severity 90
b
d
a
c
Risks Relative Risk
60
305
56
8,979
116
9,284
51.7%
3.2%
Total
All Patients Based on Severity of Illness ONLY
x16
The high relative risk show that severity of illness is a CONFOUNDER.
Scenario 2
Summary – Relative Risk of Death
Bedsore vs. No Bedsore 3
Bedsore vs. No Bedsore
(High Severity Illness)1
Bedsore vs. No Bedsore (Low Severity Illness)
1
High Severity vs. Low Severity Illness
16
Confounding
Is the association due to confounding?
1. Cause
2. Chance
3. Bias
Reverse Time Order
4.
5. Confounding
44
National Research Council , Learning and Understanding
Teach Epidemiology
Enduring Epidemiological Understandings
Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”
TYPES OF BIASTYPES OF BIAS
Using the definitions of the Using the definitions of the types of bias given, match the types of bias given, match the
following phrases with the following phrases with the appropriate bias.appropriate bias.
Name the BiasName the Bias
epidemiologist asks specific epidemiologist asks specific questions to casequestions to case
Information BiasInformation Bias
Name the BiasName the Bias
Heightened knowledge of riskHeightened knowledge of risk
Awareness BiasAwareness Bias
Name the BiasName the Bias
spends more time on casespends more time on case
Information BiasInformation Bias
Name the BiasName the Bias
error in sampling processerror in sampling process
Selection Bias Selection Bias
Name the BiasName the Bias
Higher focus on past behaviorsHigher focus on past behaviors
Recall BiasRecall Bias
Name the BiasName the Bias
more than one disease presentmore than one disease present
Berkson’s BiasBerkson’s Bias
Name the BiasName the Bias
fabrication of informationfabrication of information
Recall BiasRecall Bias
Name the BiasName the Bias
probes for more with caseprobes for more with case
Information BiasInformation Bias
Name the BiasName the Bias
unbalanced in comparison to target unbalanced in comparison to target populationpopulation
Berkson’s BiasBerkson’s Bias
67
National Research Council , Learning and Understanding
Teach Epidemiology
Enduring Epidemiological Understandings
Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”
92
National Research Council , Learning and Understanding
Teach Epidemiology
Enduring Epidemiological Understandings
Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”
96
National Research Council , Learning and Understanding
Teach Epidemiology
Enduring Epidemiological Understandings
Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”
Teach Epidemiology - 501 (Monday) CDC June 2009
98
John Snow, MD
(1813-1858)
Father of Epidemiology
“On the Mode and
Transmission of Cholera”
Identifying Patterns and Formulating Hypotheses
Teach Epidemiology - 501 (Monday) CDC June 2009
A Mysterious Ailment
By Jerry Bishop, Staff Reporter of the Wall Street Journal
A mysterious, often fatal illness is breaking out in epidemic proportions among young homosexual men and drug users. More than 180 cases of the strange illness have been reported since last summer to the federal Center for Disease Control in Atlanta. As of last Friday, at least 74 of the victims have died. All the victims are men and 90% of them are either homosexual or bisexual. Many of the victims are drug users. The illness is characterized by months of fever, malaise, and drastic weight loss. In almost all cases the patients develop overwhelming infections of one or more of a dozen different viruses, bacteria or protozoa. The infecting microbes are types that do not ordinarily cause overt human disease. Many of the patients also develop a rare type of cancer. To the astonishment of medical scientists, most of the patients appear to have recently developed a defect in their immune systems that prevents them from fighting off infections. The infections are extremely difficult to control with antibiotics and antiviral drugs. "We are reasonably confident that this is, in fact, a new medical problem," said Dr. Harold Jaffe, an epidemiologist on a new task force organized by the Center for Disease Control to search for the cause of the illness. In an effort comparable to that launched last year to unravel the mystery of toxic shock syndrome, the center's task force is trying to find out whether a new germ has emerged or whether something in the environment has changed to account for the sudden outbreak of the illness. For example, the task force is checking into the use of sexual stimulants by the victims on the possibility these chemicals can impair the immune system and leave the user vulnerable to infections. Among such stimulants are chemicals that are inhaled. These include amyl nitrate sold in glass vials, known by the street name "poppers" and isobutyl nitrate sold as "liquid incense." First hints that some unusual illness was breaking out came earlier this year when researchers in New York and Los Angeles reported cases of both a rare kind of pneumonia and a rare cancer called Kaposi's sarcoma occurring in a few young men. The men were either homosexual or drug users or both. The disease center alerted doctors and health officials around the country last summer to the strange ailment. This week's New England Journal of Medicine, published today, devotes three articles to describing 19 of the patients, six of whom died. Publishing three lengthy articles on the same illness is unusual for the medical
Identifying Patterns and Formulating Hypotheses
Teach Epidemiology - 501 (Monday) CDC June 2009
101
1998
Obesity Trends* Among U.S. AdultsBRFSS, 1990, 1998, 2006
(*BMI 30, or about 30 lbs. overweight for 5’4” person)
2006
1990
No Data <10% 10%–14% 15%–19% 20%–24% 25%–29% ≥30%
104
Whistles
What’s My Hypothesis?
Teach Epidemiology
Identifying Patterns and Formulating Hypotheses
107
National Research Council , Learning and Understanding
Teach Epidemiology
Enduring Epidemiological Understandings
Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”
108Teach Epidemiology
Enduring Epidemiological Understandings
Ken Bain, What the Best College Teachers Do
“… they can distinguish between foundational concepts and elaborations or illustrations of those ideas.”
111
Risk of
Negative Heroin
Test
Nothing
Bupe
Total
Trial 1 Trial 2
Trial 3 Trial 4
Bupe
No Bupe
Bupe
No Bupe
Bupe
TotalRelative
Risk
No Bupe
TotalRelative
Risk
Total
Tested Negative
for Heroin
Tested Positive
for HeroinRelative
Risk
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
Risk of
Negative Heroin
Test
Tested Negative
for Heroin
Tested Positive
for Heroin
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
10010021 79
90or 21%
21
100
10021 7990
or 21%21
100
Bupe is not associated with having a negative tests for heroin.
1
10062 3890
or 62%62
100
Bupe is associated with having a positive test for heroin!
.34
1006 9490
or 6%6
100
Bupe is associated with having a negative test for heroin.
3.5
Nothing
Compared to what?
Making Group Comparisons and Identifying Associations
Teach Epidemiology
112
Buprenorphine
Buprenorphine & Naloxone
Placebo
Making Group Comparisons and Identifying Associations
Teach Epidemiology
DrugEpi 3-5 Fundamentals of Study Design
Controlled Trial
Healthy People
-
Healthy People
E
Random Assignment
E
DZ
DZ
DZ
DZ
Cohort Study
Healthy People
-
Healthy People
E
E
DZ
DZ
DZ
DZ
Cross-Sectional Study
-
E
E
DZ
DZ
Case-Control Study
-
DZ
DZ
E
E
E
E
Making Group Comparisons and Identifying Associations
Teach Epidemiology
Test the hypothesis:
People who watch more TV eat more junk food.
Making Group Comparisons and Identifying Associations
Teach Epidemiology
118Teach Epidemiology
Enduring Epidemiological Understandings
National Research Council , Learning and Understanding
Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”
119Teach Epidemiology
Enduring Epidemiological Understandings
Ken Bain, What the Best College Teachers Do
“… they can distinguish between foundational concepts and elaborations or illustrations of those ideas.”
122
Relative Risks
Greater than 1 Less than 1
1
By ChanceBy Chance
25 cards25 cards25 cards25 cards
Teach Epidemiology
Explaining Associations and Judging Causality
127
National Research Council , Learning and Understanding
Teach Epidemiology
Enduring Epidemiological Understandings
Knowledge that “… is connected and organized, and … ‘conditionalized’ to specify the context in which it is applicable.”
128Teach Epidemiology
Enduring Epidemiological Understandings
Ken Bain, What the Best College Teachers Do
“… they can distinguish between foundational concepts and elaborations or illustrations of those ideas.”
130
Hypothesis
Total Risk Relative Risk
a b
c d
or %
or %Exposure Outcome
?Turned Up Together
Healthy People
-
Healthy People
E
E
DZ
DZ
DZ
DZ
Teach Epidemiology
Enduring Epidemiological Understandings
132
1.
2.
3.
4.
5.
6.
7.
8.
.
Empowers students to be scientifically literate participants in the democratic decision-making process concerning public health policy.
Empowers students to make more informed personal health-related decisions.
Increases students’ media literacy and their understanding of public health messages.
Increases students’ understanding of the basis for determining risk.
Improves students’ mathematical and scientific literacy.
Expands students’ understanding of scientific methods and develops their critical thinking skills.
Provides students with another mechanism for exploring important, real world questions about their health and the health of others.
Introduces students to an array of career paths related to the public’s health.
Top 8 Reasons to Teach / Learn about Epidemiology
Teach Epidemiology
133
Workshop Goal
Teach Epidemiology
To increase the frequency with which epidemiology is taught to students in grades 6-12
Teach Epidemiology
Innovation
… an idea, practice or object that is perceived as new by an individual or other unit of adoption.
Everett M. Rogers, Diffusion of Innovations
Workshop Goal
Diffusion
The process by which an innovation is communicated through certain channels over time among the members of a social system
(with the aim being to maximize the exposure and reach of innovations, strategies, or programs.)
Everett M. Rogers, Diffusion of Innovations
Teach Epidemiology
Workshop Goal
137
Explore Public Health Career Paths
http://www.asph.org/document.cfm?page=1038
Teach Epidemiology
What do you mean - Teach Epidemiology?
138
Leverage the Young Epidemiology Scholars Competition
http://www.collegeboard.com/yes/
Teach Epidemiology
What do you mean - Teach Epidemiology?
139
Leverage the Science Olympiad Competition
http://soinc.org/
Teach Epidemiology
What do you mean - Teach Epidemiology?
140
Show and Discuss Is Epidemiology in Your Future?
http://www.rwjf.org/pr/product.jsp?id=26931#content
Teach Epidemiology
What do you mean - Teach Epidemiology?
141
Infuse Epidemiology into Existing Lesson about Something Else
Teach Epidemiology
What do you mean - Teach Epidemiology?
142
Teaching Existing Epidemiology Lessons
http://www.collegeboard.com/yes/ft/iu/units.html
Teach Epidemiology
What do you mean - Teach Epidemiology?
143
Teaching Existing Epidemiology Lessons
http://ccnmtl.columbia.edu/projects/epiville/
Teach Epidemiology
What do you mean - Teach Epidemiology?
144
Teaching Existing Epidemiology Lessons
http://www.diseasedetectives.org/
Teach Epidemiology
What do you mean - Teach Epidemiology?
145
Teaching Existing Epidemiology Lessons
http://www.cdc.gov/excite/
Teach Epidemiology
What do you mean - Teach Epidemiology?
146
Teaching Existing Epidemiology Lessons
http://www2a.cdc.gov/epicasestudies/
Teach Epidemiology
What do you mean - Teach Epidemiology?
147
Teaching Existing Epidemiology Lessons
http://www.cdc.gov/excite/ScienceAmbassador/ScienceAmbassador.htm
Teach Epidemiology
What do you mean - Teach Epidemiology?
148
Teaching Existing Epidemiology Lessons
http://www.buffetbusters.ca/
Teach Epidemiology
What do you mean - Teach Epidemiology?
149
Teaching Existing Epidemiology Lessons
http://www.montclair.edu/Detectives/
Teach Epidemiology
What do you mean - Teach Epidemiology?
150
Teaching Existing Epidemiology Lessons
http://www.montclair.edu/drugepi/
Teach Epidemiology
What do you mean - Teach Epidemiology?
151
View a News Item from an Epidemiologic Perspective
http://www.nationalacademies.org/headlines/
Teach Epidemiology
What do you mean - Teach Epidemiology?
Teach Epidemiology
During the coming school year, participate in an online Teach Epidemiology In the News - Social Network
and teach epidemiology.
What do you mean - Teach Epidemiology?