Ecological Studies

Question 1

Type of study, usefulness, what examines

Answer 1

Descriptive study: useful for making hypotheses

Examines the relationship between exposures (global exposure to a risk factor) and disease with population level

Question 2

Types of variables

Answer 2

• Aggregated variables
• Environmental exposures
• Global traits

Question 3

Advantages

Answer 3

• Simple and easy to understand
• Economical
• Based on pre-existing data
• There is a lower exposure variability in individual studies
• Importance of studying possible true ecological relationships
• Can suggest avenues of research that may be promising in casting light on ecological relationships

Question 4

Better when (more useful for)

Answer 4

When exposures are controlled or clearly ecological

(Tobacco bans and alcohol bans - does it reduce prevalence of consumption of substances?)

Question 5

Disadvantages

Answer 5

Only hypothesis, no analysis

By themselves, they don’t demonstrate conclusively that a causal association exists

Even a temporal sequence may be questionable

Ecological fallacy and bias

Question 6

Ecological fallacy

Answer 6

An association observed between variables on the aggregate level doesn’t necessarily represent the association that exists at the individual level

Question 7

Time-series studies

Answer 7

Frequency of a given disease/condition is compared along time in a specific geographical

Question 8

Time-series studies; characteristics, usefulness

Answer 8

Allows us to see population changes
Geographical area stays constant
Based on aggregated data

To generate hypotheses and to make predictions

Question 9

Time-series studies limitations

Answer 9

• Changes in disease condification
• Changes in diagnostic criteria