Lecture 9: Cross sectional studies

Question 1

What is descriptive epidemiology?

Answer 1

• Describe the occurrence of disease and/or outcome
• Studies the disease occurrence by person, place and time
• Describes WHO, WHAT and WHEN

Question 2

What is analytical epidemiology?

Answer 2

• Incorporates the analysis of associations between exposure and disease
• when you find associations btw exposure and outcome to see if it is the determinant of the health outcome

Question 3

What is the ECOLOGICAL study design?

Answer 3

• It compares the prevalence of exposure and occurrence of disease in POPULATIONS or groups of people, NOT individuals
• When you want to compare 2 groups to each other

Question 4

What are the weakness of Ecological studies?

What is ecological fallacy

Answer 4

1. Ecological fallacy
   = association at the group level may not actually may not actually hold true at the individual level
2. Controlling confounding
3. Showing causation

Question 5

What is cross sectional studies?

Answer 5

• It examines the relationship btw the diseases and other variables of interest as they exist in a defined population
• combines descriptive & analytic components
• captures prevalence
• measures exposure and outcome at the same time

Question 6

What are the strengths of cross sectional studies?

Answer 6

• exposure and outcome are both assessed at the same time

- potenital cheap and easy

Question 7

What are the weaknesses of cross sectional studies?

Answer 7

• hard to determine whether the exposure of outcome came first
• TEMPORAL sequencing - need to demonstrate causation
• Hard if outcomes/exposures are are: rare, transient(appear then disappear) or variable. You need to have a large population