Cohort Studies

Question 1

What are the 2 main types of studies conducted in epidemiology?

Answer 1

• observational

- interventional

Question 2

What are the types of observational studies?

Answer 2

Cohort studies
Case-controls studies
Cross-sectional studies

Question 3

What are the types of interventional studies?

Answer 3

randomised controlled trials

Question 4

What is a cohort study?

Answer 4

Study in which one or more cohorts are followed prospectively and it is established if exposure to certain condition(s) can cause a disease
- relate info on disease occurrence to exposure

Question 5

What is a case control study?

Answer 5

Opposite of a cohort study

- finding out from people with the disease what they were exposed to that could have led to it

Question 6

What is the bias in cohort studies?

Answer 6

• loss to follow up
• exposure measured at 1 time point
• selection of cohort

Question 7

What are the disadvantages of cohort studies?

Answer 7

• take a long time
• need a lot of people
• very expensive

Question 8

What is the relationship between incidence and risk?

Answer 8

• incidence usually taken to be a measure risk

- number of new cases of a disease/deaths per 100,000 people per year

Question 9

What is relative risk?

Answer 9

incidence of disease in exposure population/incidence of disease in unexposed population

Question 10

What is a confounder?

Answer 10

a factor associated with the exposure and with the disease

- can adjust confounders

Question 11

What is survival analysis measured by?

Answer 11

• how long someone lives
  Kaplan Meier curves
• plot proportion of people surviving overtime
• calculate hazard ratios
• give risk of dying at any point in time in 1 group compared to the other

Question 12

What is absolute excess risk?

Answer 12

Risk in exposed - risk in unexposed

Question 13

What is attributable proportion?

Answer 13

Calculate the increase in cases and compare to the whole population
- incidence in population attributable to exposure/incidence In population

Question 14

When do 95% confidence intervals suggest the data is statistically significant?

Answer 14

• 95% CI for a difference in means includes 0 = not statistically significant, excludes 0 = is
• 95% CI for a relative risk includes 1 = not, excludes 1 is

Question 15

What are the 2 measures of importance?

Answer 15

• absolute excess risk

- attributable proportion

Question 16

How do you calculate attributable proportion?

Answer 16

p(relative risk -1)/1+p(relative risk -1)

p = proportion exposed in population