HHE 450: Chapter's 6 & 7 & 8

What is an Epidemiological Study?

A study useful for conducting the relationship between an exposure of interest and a disease/outcome of interest with validity and precision using a minimal amount of resources.

What are the (3) Components of The Epidemiologic Study Design Triangle?

1) Research Question & Hypothesis

2) Study Design

3) Analytic Plan

What is the Weakest Basic Study Design?

Clinical Observation

What is the Strongest Basic Study Design?

Systematic Review

What (5) Things does Study Design in Epidemiology Depend On?

1) The Research Question

2) Resources & Time Available for Study Completion

3) Type of Outcome of Interest

4) Type of Exposure of Interest

5) Ethics

What (4) Things does Study Design in Epidemiology Include?

1) The Research Question & Hypothesis

2) Measures & Quality of Data

3) Time

4) Study Population

What are the (2) Types of Epidemiology?

1) Descriptive Epidemiology

2) Analytic/Scientific Epidemiology

What is Analytic/Scientific Epidemiology?

A form of Epidemiology that evaluates hypothesis relating to the cause of disease & determines the success of intervention programs.

What are the (6) Components of a Study?

1) Population

2) Exposure

3) Outcome

4) Potential Confounders

5) Analysis

6) Communication of Findings

What are the (2) Types of Analytic/Scientific Studies?

1) Experimental

2) Observational

What is an Experimental Study?

A study in which the investigator actively manipulates which group receives agents under the study.

Its purpose is to study prevention and treatments for diseases.

Investigator typically randomly assigns treatment & comparison groups.

Example: Clinical Trial

What is an Observational Study?

A study in which the investigator observes as nature takes its course.

Examples: Cohort, Case-Control, Cross-Sectional

What are Pros & Cons of Experimental Studies?

Pros: Most Rigid Research Methods, Standardized, Easier to Establish Cause & Effect

Cons: Long Preparation Time, Incredibly Detailed, Artificial Setting

What is a Cohort Study?

A form of observational study in which the investigator selects subjects according to their exposure levels and then follows them for disease occurrence.

Based on disease data collection we can identify which type of cohort study is being investigated.

Types of Cohort Studies: Retrospective, Prospective, Ambidirectional

What are the Pros & Cons of Cohort Studies?

Pros: Establishes Risk Directly, Assesses Multiple Outcomes of Disease, Can Track Rare Exposures Well

Cons: Expensive, Timely, Does Not Track Diseases with Long Latency Periods Well

What is a Case-Control Study?

A study in which the subjects are identified as having the disease OR are from the source population that gave rise to the cases and from this exposure distribution is compared.

This study is useful when very little is known about the disease itself.

What are the Pros & Cons of Case-Control Studies?

Pros: Cheap, Quick, Multiple Exposure Assessment, Works Well for Rare Disease Assessment & Diseases with Long Latency Periods

Cons: Only Able to Assess 1 Disease Outcome, Cannot Establish Risk or Prevalence

What is an Ecological Study?

A study which examines the rates of disease in relation to a population factor.

The unit of measurement is population rather than individuals.

What are the Pros & Cons of an Ecological Study?

Pros: Low Cost, Wide Range of Exposure Levels, Ability to Examine Contextual Effects on Health

Cons: Unable to Fill Out a 2×2 Table, No Way of Detecting Subtle Changes Due to the Crude Data

What is a Cross-Sectional Study?

A study which measures exposure and disease at one point in time.

“A Snapshot of the Population”

What is a Retrospective Cohort Study?

A study in which exposure and outcome have already occurred.

Existing records are used.

What is a Prospective Cohort Study?

A study in which exposure status is identified and participants are to be followed into the future to watch for disease development.

What is an Ambidirectional Cohort Study?

A study in which existing records are used to follow participants forward in time.

If experimental studies can measure the incidence of outcome among two populations, what measure(s) of disease association can be calculated?

Risk Ratio & Risk Difference

What is Equipoise?

A state in which investigators truly do not know whether one treatment is better than another, but truly believe that withholding treatment from study participants will not harm them.

True or False: Experimental Studies are Only Appropriate & Ethical when Equipoise is Present

True

What is a Prevention Trial?

A trial in which an agent is given to healthy or high-risk individuals to prevent disease occurrence.

What is a Therapeutic Clinical Trial?

A trial in which an agent is given to diseases individuals to treat or cure.

What is the (6) Step Process of Experimental Studies?

1) Research Questions for Experimental Study

2) Identify Type of Experimental Study

3) Identify Study Population

4) Achieve Consent, Enrollment, & Exposure Assignment

5) Minimize Bias

6) Analysis

What are the (2) Units of Allocation?

Individual Trial & Community Trial

What does Choice of Population Depend On?

The Identified Purpose of Trial

What is Generalizability?

The extent to which the results from a study can be generalized or extended to people who did not participate in the study directly.

What is a Reference Population?

A group of people to whom results of the trial are applicable/generalizable.

What is Required to Determine a True Difference Between Treatment & Comparison Groups?

Enrollment of an Adequate Number of Study Subjects

What is Statistical Power?

The ability to demonstrate an assocation if one exists.

Power Ranges From 0-100% (Good Power = +80%)

Who Must Approve Study Protocol Before Initiating Procedures?

Institutional Review Board (IRB)

What is Informed Consent?

A process that all eligible individuals must give before enrolling in a trial.

This includes clear explanation of research goals and methods, risks & benefits of participating, assurance of confidentiality, and the right to withdrawal.

What is Randomization?

The idea that each study participant has the same probability of receiving treatment.

This prevents bias group assignment & minimizes inaccurate results caused by confounding.

What is a Confounder?

A factor that distorts the true association between an exposure and an outcome.

What is the Ultimate Goal of Randomization Balancing Confounders?

That treatment is the only difference between study groups

Why is Random Standardized Control Trial the Gold Standard of Research? (Open-Ended Exam #2 Question)

The trial design eliminates bias and proves a direct cause & effect relationship.

What does Randomization Prevent?

Biased Group Assignments

What is Blinding/Masking?

A method of ensuring that participants and/or study investigators have no knowledge of whether a study participant has been assigned to the treatment or comparison group.

What is a Single Blind Study?

The study participant does not know whether he or she is receiving treatment or no treatment.

What is a Double Blind Study?

Neither the (1) study participant nor the (2) study investigator administering the treatment knows who is receiving treatment or no treatment.

What is a Triple Blind Study?

Neither the (1) study participant nor the (2) study investigator administering the treatment nor the (3) study investigator monitoring the effects of the treatment knows who is receiving treatment or no treatment.

What is Compliance?

The act of following the study protocol exactly as required throughout the course of the trial.

Noncompliance tends to make treatment and comparison groups more alike, reducing the ability to detect differences between groups.

Within Analysis What Measures of Frequency/Association are Important for Setting Up 2×2 Table?

Cumulative Incidence & Incidence Rate (Treatment & Comparison Group)

Rate Difference & Risk Ratio (Treatment & Comparison Group)

What are the (3) Ways to Minimize Bias?

1) Blinding/Masking Studies

2) Placebo

3) Encouragement of Compliance

What is a Randomized Control Trial?

A trial in which participants are randomly allocated.

What is a Non-Randomized Control Trial?

A trial in which participants are not randomly allocated.

What is a Cohort Study?

A study in which people who are free of disease and that differ according to exposure (exposed and unexposed) are followed over time for incidence of disease.

What are General Cohorts?

A type of cohort that investigates common exposures within the general population.

Within this type of cohort investigators can study effects of multiple exposures on one or more outcomes.

Examples: Smoking, Alcohol Consumption, Blood Pressure

What are Specialized Cohorts?

A type of cohort that investigates unusual and rare exposures.

Within this type of cohort investigators can study effects of only one exposures on one or more outcomes.

Examples: Atomic Bomb Survivors, Agent Orange Vietnam Veterans, Occupational Exposures

Determining to Use General or Specialized Cohorts is Reliant on?

1) Study Hypothesis

2) Feasibility

What is the Framingham Heart Study? (General Cohort Example)

Framingham, Massachusetts

The study objective was to identify characteristics that contribute to Cardiovascular Disease by following healthy individuals.

What is the Counterfactual Ideal?

An ideal comparison group would be the exact same people who are in the exposed group had they not been exposed.

What are the (3) Types of Comparison Groups?

1) Internal Comparison

2) Comparison Cohort

3) General Population Comparison

What is “The Healthy Worker Effect” in Occupational Cohort Studies?

Rates of morbidity and mortality among a working population are lower than those of the general population.

Which comparison group will lead to the “Healthy Worker Effect?”

General Population Comparison

What are (3) Sources of Exposure Information?

Pre-Existing Records, Questionnaires/Interviews, & Direct Testing

What is meant by the term Follow-Up?

The only valid way “out” of a cohort study is to develop the disease within the study, to die, or for the study to end.

The ultimate goal is to obtain complete follow-up information on all subjects regardless of exposure status.

What are the (4) Strategies to Manage Follow-Up?

1) Select Interested Participants

2) Collect Identifiable Information

3) Maintain Frequent Contact with Respondents

4) Offer Incentives

What are (3) Strengths of Cohort Studies?

1) Clear Temporal Sequence is Identified Between Exposure & Disease

2) Effective for Rare Exposures

3) Ability to Study Effects of an Exposure on Multiple Outcomes

What are (3) Weaknesses of Cohort Studies?

1) Large # of Subjects is Required for Long Periods of Following

2) Non-Effective for Rare Diseases/Long Latency Diseases

3) $$$ & Time-Consuming

Why are Cohort Studies Non-Effective for Studying Rare Diseases?

This is because the number of participants needed to accumulate a number of cases of disease over a particular study period is challenging and ultimately unfeasible.