Module 4 part 1

Question 1

what is Descriptive Epidemiology

Answer 1

‘Person, place and time’
* Observational, it is What
* Who
* Where
* When

Question 2

What is Analytic Epidemiology

Answer 2

Associations: exposures
and outcomes.
Causation
* Observational or
intervention studies

Question 3

What are the 5 study types

Answer 3

Cross-sectional, ecological studies, Cohort studies, Case-control studies, Randomised-controlled trials

Question 4

what studies are Descriptive
epidemiology

Answer 4

Cross-sectional and ecological studies

Question 5

What studies are Analytic
epidemiology

Answer 5

All 5 but mainly Cohort studies, Case-control studies, Randomised-controlled trials

Question 6

What is a cross-sectional study?

Answer 6

Measures exposures and/or outcomes at one point in time

Question 7

What do cross-sectional studies
measure?

Answer 7

Prevalence: the proportion of a defined population who have a disease at a point in time

Question 8

Equation for prevalence

Answer 8

Prevalence = number of people with disease at a given point in time / total number of people in the population at that point in time

Question 9

Cross-sectional studies can be used to d______, C_______ and G______ H______

Answer 9

DESCRIBE ( EgWhat is the prevalence of osteoarthritis in NZ?), COMPARE ( E.g. What is the prevalence of
osteoarthritis in NZ for people of different ages?) and GENERATE HYPOTHESIS (E.g. Which factors are associated with low back
pain among nurses?)

Question 10

Components of “The GATE frame?” used for Epidemiological

Answer 10

Population (source), Exposure/Comparison (exposed group and unexposed group) and Outcome ( positive or negative for certain disease.

Question 11

Do Epidemiological and cross sectional studies show causation. Why?

Answer 11

No, because exposure and outcome are Measured at the same Time

Question 12

Limitations of cross-sectional studies? (4)

Answer 12

Temporal sequencing, Measures prevalence not incidence, Not good for studying rare outcomes or exposures, Not good for assessing variable and transient exposures or
outcomes

Question 13

What is prevalence vs incidence

Answer 13

Incidence is a measure of the number of new cases of a characteristic that develop in a population in a specified time period; whereas prevalence is the proportion of a population who have a specific characteristic in a given time period, regardless of when they first developed the characteristic.

Question 14

Incidence proportion?

Answer 14

measures the probability of developing a disease or health event over a specified time ((Number of new cases during a specific time period) / (Number of people at risk during that same time period).

Question 15

why do cross-sectional studies? (strengths)

Answer 15

Can assess multiple exposures and outcomes, Can be less expensive than some other study designs, Relatively quick, Hypothesis generating

Question 16

what are Ecological studies

Answer 16

Compare exposures and outcomes across GROUPS not individuals

Question 17

What are ecological studies used for?

Answer 17

To compare between populations, To assess population level factors, To consider hypotheses

Question 18

Weaknesses of ecological studies

Answer 18

ecological fallacy (a logical error where inferences about individuals are made from group-level data.), doesn’t show causation,

Question 19

why do ecological studies?

Answer 19

Population level exposures, Consideration of hypotheses, May be relatively easy to do, May be relatively inexpensive

Question 20

What is Temporal sequence

Answer 20

the order in which events or data points occur over time.

Question 21

what are two Measures of
association

Answer 21

Relative (Relative Risk), Absolute
(Risk Difference)

Question 22

Relative risk, what does this tell us and calculation

Answer 22

“Null Value”. Ratio of the incidences, How many times as likely is the exposed group to develop the outcome than the comparison group? IExposed / IComparison = Relative Risk

Question 23

what is Absolute
(Risk Difference) and what is alternative name

Answer 23

“Attributable Risk” How many extra/fewer cases of the outcome in the exposed group are attributable to the exposure?
IE − IC

Question 24

Explain what is means if incidence of exposed group is 50% and incidence of control group is 25% in terms of absolute risk

Answer 24

50-25 therefor There were 25 extra cases per 100 people over one year of (outcome eg disease) in (exposed group) compared to (control group) but Report differently for incidence proportion and
incidence rate

Question 25

Relative risk vs risk difference

Answer 25

Relative risk= Clues to aetiology (causes), Strength of association Risk difference= Impact of exposure, Impact of removing exposure Both are important

Question 26

What is a cohort study?

Answer 26

“…individuals are defined on the basis of presence or absence of exposure to a suspected risk factor” exposed vs not exposed over time.... do they develop a certain outcome

Question 27

Cohort studies step by step

Answer 27

1. Identify a source population, 2. Recruit your sample population (Sample population must not already have the outcome of interest), 3. Assess exposure to identify which group participants belong in (exposed or not exposed i.e. comparison, 4. Follow up over time and Observe whether or not participants develop the outcome

Question 28

Ways to gather data from cohort studies?

Answer 28

Calculate measures of occurrence and measures of association

Question 29

Two types of Measures of occurrence

Answer 29

Incidence proportion= Number of people who develop the disease in a specific period / Number of people at risk of developing the disease at the start of the period Incidence rate= Number of people who develop the disease in a specific period / Number of person-years at risk of developing the disease

Question 30

Two types of measures of association (two types for both)

Answer 30

Relative risk (2 types: rate and proportion) 1. Rate ratio= IRE / IRC 2. Risk ratio = IPE / IPC Risk difference: IRE – IRC and IPE - IPC

Question 31

Limitations of cohort studies

Answer 31

Potential for misclassification of exposures/outcomes, Time consuming, Can be expensive

Question 32

Strengths of cohort studies

Answer 32

Determine temporal sequence between exposure and outcome, Can examine multiple outcomes from an exposure, Can calculate incidence (and therefore relative risk and risk difference), Good for studying rare exposures

Question 33

Two types of Cohort studies

Answer 33

1. Prospective cohort studies 2. Historical cohort studies (Sometimes called retrospective cohort studies)

Question 34

Difference between Prospective cohort studies and Historical cohort studies (it long)

Answer 34

Prospective cohort studies follow a group forward in time to observe outcomes from baseline, providing detailed, real-time data but requiring long follow-ups and risking loss to follow-up. Historical (retrospective) cohort studies use existing past data to look backward in time, identifying exposures and outcomes that have already occurred, offering speed and cost-efficiency but with less control over data quality and a higher risk of bias

Question 35

Important tip (look up until you get it)

Answer 35

Make sure you understand the difference between historical cohort studies, case-control studies and cross-sectional studies