Epidemiology 7076 Final

Front 1

Animal Studies-disadvantages

Back 1

1. Dosage effects difficult to replicate in humans

2. Human diseases may not occur in animals

3. Difficult to extrapolate data

Front 2

Unplanned or natural experiments

Back 2

1. Exposure occurs due to lifestyle, accident, or occupation

Front 3

Human studies sequence

Back 3

1. Clinical observation at the bedside

2. ID routinely available data

3. Design/carry out new study: case control then cohort the RCT (for beneficial agents) typically

Front 4

Two step process for carrying out studies & evaluating evidence

Back 4

1. Group characteristic studies (ecologic studies)

then Individual characteristic studies (case-control, cohort, RCT)

2. Determine if observed association is causal

Front 5

Indirect and direct causal relationships (def)

Back 5

1. Direct-a factor directly causes a disease without any intermediate step

2. Indirect-a factor causes a disease after intermediate step or steps

In human biology, intermediate steps are nearly always present in any causal process

Front 6

Types of causal relationships

Back 6

1. Necessary and sufficient

2. Necessary but not sufficient

3. Sufficient, but not necessary

4. Neither sufficient nor necessary

Front 7

Necessary and sufficient

Back 7

Without the factor, the disease never developsWith the factor, the disease always develops

RARELY IF EVER OCCURS

Front 8

Necessary, but not sufficient

Back 8

The factor is necessary but not in itself sufficient to cause the disease. Multiple factors, often temporal, are required

example: cancer requires initiation and promotion

Front 9

Sufficient, but not necessary

Back 9

The factor alone can produce the disease, but so can other factors

example: radiation can initiate cancer, but so can tobacco use, genetics, etc. Sufficient is rarely met by a single factor

Front 10

Neither sufficient nor necessary

Back 10

The factor alone cannot instigate the disease, and other factors can also initiate disease

Most accurate representation

Front 11

Hill's Postulates: Guidelines for judging observed relationship as causal

Back 11

1. Temporal relationship 2. Strength of association 3. Dose-response relationship 4. Replication of findings 5. Biologic possibility 6. Consideration of alternate explanations 7. Cessation of exposure 8. Consistency with other knowledge 9. Specificity of association

Front 12

Importance of temporal relationship

Back 12

1. exposure must predate disease

2. establish interval between exposure and disease

Front 13

Measuring strength of association

Back 13

relative risk or odds ratio-the higher the RR or OR, the stronger the association and the more likely the association is causal

Front 14

Considerations for dose-response

Back 14

If threshold exists, no disease may exist below threshold

A dose-response relationship is a strong indication of a causal association

Front 15

US Preventative Services Task Force considerations (study rankings)

Back 15

1. Quality of study 2. Strength of evidence 3. Estimate of benefit/harms 4. Net benefit assessed (high, moderate, low).

Given Grade A/B (recommends), C (not routine, but if risk), D (discourage), I (insufficient)