1. Review – First Exam Chapters 1 through 5
Review questions at the end of the chapters are good
Focus on Key Concepts
Don’t need to know specifics from Chapter 4 which includes information on sources of public health data.
Exam 10/04 and review is 9/27
Project Question and Aim due 10/2

2. Overview of Epidemiologic Study Designs

3. Questions to Ask Exposure  Outcome
How should you define your exposure(s)?
In which people?
How should you define your disease?
How can you make your study accurate?
Bias
Confounding
Random error
How can you make your study efficient?
Time
Money

4. Experimental Study Purpose Key Feature Setting
Study preventions and treatments for diseases.
Key Feature
Investigator assigns individuals to two or more groups that either do or do not receive a preventive or therapeutic agent and follows the groups for incidence of outcome.
Setting
Ethical and feasible
Able to detect even a small effect
Money is available – most expensive study design

6. Cohort Study Purpose Key Feature causes preventions treatments
Subjects selected based on exposure
Followed for disease occurrence

7. Cohort Study Setting Trial not ethical, feasible, or too expensive
Moderate or large effect expected
Little known about exposure and so can evaluate many effects of an exposure
Exposure is rare
Underlying population is fixed

9. Cross-Sectional Study
Purpose
Descriptive, prevalence
Associations
Key Feature
Random sample of a population, or weighted sample
Single time point

10. Cross-Sectional Study
Setting
Initial/early study of exposure  outcome relationship
Descriptive information needed
Trial not ethical, feasible, or too expensive.
Moderate or large effect expected.
Little known about exposure or outcome.
Neither exposure or outcome is too rare.

11. Case-Control Study Purpose Key Feature Studies causes
Preventions and treatments for diseases.
Key Feature
Sample based on case-control status
CASE – Method of sampling cases.
CONTROL – source population that gave rise to the cases (controls)
Compare exposure distribution in cases and controls

12. Case-Control Study Setting
Trial not ethical, feasible, or too expensive.
Moderate or large effect expected.
Little known about disease and so can evaluate many exposures.
Disease is rare.
Underlying population is dynamic.

14. Ecologic Study Purpose Key Features
Very early stage of investigating exposure  outcome
Key Features
Unit of analysis is at the level of the group level
Example – per capita sugar consumption per country and incident rates of diabetes

15. Which type of design is being described in each of the following scenarios?
A study that evaluates the relationship between breast cancer and a woman’s history of breast feeding. The investigator selects women with breast cancer and an age-matched sample of women who live in the same neighborhoods as the women with breast cancer. Study subjects are interviewed to determine if they breastfed any of their children.

16. Which type of design is being described in each of the following scenarios?
A study that evaluates two treatments for breast cancer. Women with stage 1 breast cancer are randomized to receive either lumpectomy alone or lumpectomy with breast radiation. Women are followed for five years to determine if there are any differences in breast cancer recurrence and survival.

17. Which type of design is being described in each of the following scenarios?
A study of the relationship between exposure to chest irradiation and subsequent risk of breast cancer that was begun in In this study, women who received radiation therapy for post-partum mastitis in the 1940s were compared to women who received a non-radiation therapy for post-partum mastitis in the 1940s. The women were followed until 2001 to determine the incidence rates of breast cancer in each group.

18. Which type of design is being described in each of the following scenarios?
A study of the relationship between exposure to postmenopausal hormone therapy and subsequent risk of breast cancer that will begin in January In this study, postmenopausal women who receive hormone therapy during 2013 will be compared to postmenopausal women who do not receive this therapy. The women will be followed until 2023 to determine the incidence rates of breast cancer in each group.

19. Which type of design is being described in each of the following scenarios?
A study that examines the death rates from colon cancer in each of the 50 US states in relation to the average percentage of residents in each state undergoing colonoscopy screening.

20. What type of study would you use for:
Identifying causes of a rare disease
Identifying the long term effects of a rare exposure
Studying the health effects of an exposure for which information is difficult and expensive to obtain
Identifying the causes of a new disease about which little is known
Identifying the short-term health effects of a new exposure about which little is known.
Identifying the causes of a disease with a long latent period.

21. True or False
Observational studies of preventions and treatments are often conducted when experimental studies are unethical or infeasible.
The main limitation of observational studies is the investigators inability to have complete control of extraneous factors called confounders.
A cross-sectional study of the relationship between blood type and the risk of cataracts will produce misleading results because you cannot tell the correct temporal relationship between the exposure (blood type) and disease (cataracts).

22. True or False
An ecological study was done to determine the relationship between per capita soft drink consumption and mortality rates from diabetes in 10 US states. The investigators found a strong association between soft drink consumption an diabetes mortality. Based on this study, we can conclude that the individual who consumed the soft drinks were the ones who died from diabetes.
Case-control studies are inherently inferior to cohort studies.
Experimental studies are inherently superior to observational studies.

23. State the main difference between these types of studies.
Observational and experimental studies.
Retrospective and prospective cohort studies.
Cohort and case-control studies.

24. Considerations for Choosing a Particular Design
Research question
Existing scientific knowledge
Frequency of exposure and disease
Ethical considerations
Concerns about validity, random error, efficiency

25. Which study design to choose?
In theory, it's possible to use all three designs to test a hypothesis.
What are the issues in using a case-control study design?
What are the issues in using a cohort study design?
What are the issues in using an randomized clinical trial?

26. Case- Control Study E E Determines and Compares
Cases of
Lung
Cancer E
Determines and Compares
Past Vitamin A Consumption
Source
Population
Investigator
Selects E
Controls
=sample of
source pop

27. Determines and Compares Lung Cancer Incidence
Cohort Study D
High
Vitamin A
Group
Determines and Compares Lung Cancer Incidence
Source
Population
Investigator Selects
Time Passes D
Low
Vitamin A
Group

28. Determines and Compares Lung Cancer Incidence
Experimental Study
High
Vitamin A
Group
Determines and Compares Lung Cancer Incidence
Source
Population
Time Passes
Investigator
Assigns D
Low
Vitamin A
Group

29. Summary Choice of study designs balances many considerations…
Research question
Existing scientific knowledge
Frequency of exposure and disease
Ethical considerations
Concerns about validity, random error, efficiency
Efficiency – cost and time
Each design has complementary strengths and weaknesses

30. Research Proposal Research Question Hypothesis Null – no association
Alternative – an association, but no direction
Research/Operational – indicate direction
Cross-sectional surveys can have hypotheses

31. Research Question Hypothesis Hypothesis Example Null – no association
Alternative – an association, but no direction
Research/Operational – indicate direction
Cross-sectional surveys can have hypotheses
Hypothesis Example
Null – Obesity is not associated with diabetes.
Alternative – Obesity is associated with diabetes.
Research/Operational – Obese individuals have a higher risk of developing diabetes than non-obese individuals.
Cross-sectional: Obese individuals are more likely than normal weight individuals to have diabetes.

32. Research Proposal – Background and Significance Section
Magnitude of the problem – why do we care
Prevalence in the US or SC
Outcome
Exposure
Strengths – unique and novel aspects
Population available
Exposure measurement
Outcome measurement
Therefore, we propose to study X here
Background and Significance (include 4 to 8 references and use endnote for the references)

33. Key Components -- Study
Feasible – it must be possible to answer the question analytically (scientifically, time, resources)
Interesting – the question should generate interest among the consumers of the research
Novel – the question should add something new to the field of research
Ethical – procedures needed to answer the question must not compromise the protection of human subjects
Relevant – the question should address issues that are timely, have an impact on the study population, and make a contribution to the field of study