Session 5 - Cohort studies

Question 1

Cohort

Answer 1

A group of people with a shared characteristic

Question 2

Cohort Study

Answer 2

Observational study using data on individuals
Compare disease frequencies in exposed and non exposed individuals
Follows a population of disease free individuals

Question 3

Historical (retrospective) cohort study

Answer 3

Often used for occupational cohorts
Need records of exposure and disease development

Question 4

Measures of exposure, outcome, association for Cohort study

Answer 4

Permit calculation of both cumulative incidence (risk) and incidence rate
Can calculate both Rate Ratio and Risk Ratio to assess strength or relationship between exposure and outcome

Question 5

Rate ratio

Answer 5

Compares the incidence rates of two groups. It’s used when the number of subjects in a cohort changes over time. The formula for a rate ratio is the incidence rate in the exposed group divided by the incidence rate in the unexposed group.

Question 6

Risk ratio

Answer 6

Compares the risks of two groups. It’s used when the time it takes for an outcome to develop is short. The formula for a risk ratio is the risk in the exposed group divided by the risk in the unexposed group.
(occurs during a specified time period)

Question 7

Bias

Answer 7

Systematic error in the design, conduct, or analysis of
a study that leads to deviation from the truth - giving incorrect measures of association / /effect (RR, OR etc)

Question 8

Selection Bias

Answer 8

systematic difference in characteristics between study
participants and the population from which they were selected, or
between groups compared within the study
eg non-participation, loss to follow up

Question 9

Information bias (ascertainment bias)

Answer 9

Systematic differences in classification of exposure or outcome of study participants
eg measurement error, misclassification associated with disease or exposure status (if not blinded, patient or researcher may classify pain, or BP differently due to expectation of effects of exposure)

Question 10

Cumulative Incidence

Answer 10

Proportion of people at risk of disease in a population that develop disease in a specified time

Question 11

Incidence Rate

Answer 11

Number of new cases of disease in a population per unit person-time among people at risk of disease

Question 12

Risk ratio formula

Answer 12

a/(a+b) / c/(c+d)

Question 13

Odds ratio, relative risk (risk ratio) 2x2

Answer 13