Flashcards in Cohort Studies Deck (27):

1

## What are the two main types of studies?

### Observational and interventional

2

## Give an example of interventional studies.

### RCTs

3

## Given examples of observational studies. (3)

###
Cohort

Case-control

Cross-sectional

4

## How are cohort studies done?

###
Identify individuals

Measure exposures in each individual

Follow-up individuals to determine disease/disorder occurrence

Relate information on disease occurrence to exposure

5

## Explain a cohort study simplistically. (2 words)

### Cohort --> disease

6

## How do cohort studies differ from case-control studies?

###
Cohort --> disease FOR COHORT

Exposure

7

## Why might there be bias in cohort studies? (3)

###
Loss to follow-up

Exposure usually measured at just one time point

Selection of cohort

8

## What are the disadvantages of cohort studies? (3)

###
Take a long time

Need a lot of people

Very expensive

9

## What was the British Doctors Study?

### Information from 34,439 male doctors initially collected in 1951 and they were followed up for 50 years. They were asked about smoking. Death certificates obtained when they died.

10

##
What is incidence?

What is it usually taken to be a measure of?

###
Number of new cases (or deaths) of a disease per 100,000 people per year.

Risk

11

## How do you calculate relative risk?

### Incidence of disease in exposed population/incidence in unexposed population

12

## How can we tell if the results have arisen due to chance alone?

###
Look at p-values and confidence intervals

13

## If the risk of a disease is the same for the exposed and for the unexposed populations, what is the relative risk?

### 1

14

## Explain what a 95% CI of a sample relative risk means.

### The 95% CI of a sample relative risk contains the population relative risk with a probability of 95%

15

## Explain what a 95% CI of a sample mean means.

### The 95% CI of a sample mean contains the population mean with a probability of 95%

16

## When can you tell that the results (relative risks/ratios) are statistically significant looking at the 95% CI?

### If the CI doesn’t include 1 (for means, it is 0 but for risks it is 1).

17

## What is a confounder?

### A factor that is associated both with the exposure and also with the disease.

18

## How do you account for confounders?

###
Statistical adjustment

e.g. with alcohol and smoking. Analyse alcohol consumption and risk of lung cancer in non-smokers, and alcohol consumption and risk of lung cancer in smokers. You might expect these risks to be similar, in which case you could combine them.

19

## Which should you use – unadjusted or adjusted RR?

### Adjusted - this is adjusted for confounders.

20

## What curves are used for survival analysis? What do these plot?

### Kaplan-Meier curves - they plot proportion of people surviving over time.

21

## What does the log rank of a Kaplan-Meier curve compare?

###
The two curves for the exposed/unexposed population

22

## How do hazard ratios differ from relative risks?

### The take into account the time taken for the event to occur

23

## What are hazard ratios?

### They give the risk of dying at any time point in one group compared to the other

24

## What two measures of importance are given in this lecture?

###
Absolute excess risk

Attributable proportion

25

## How do you calculate the absolute excess risk?

### Risk in exposed – risk in unexposed

26

## How do you calculate the attributable proportion?

### Incidence in population attributable to exposure/incidence in population

27