Introduction to Epidemiology

Question 1

What is mortality rates? and what is needed for a meaningful statistic

Answer 1

The threat of death (death rates). A meaningful statistic needs a denominator population and a time frame.

Question 2

What are some examples of denominators used in mortality rates?

Answer 2

Health boards, cities and hospitals (it picks specific groups of people/areas)

Question 3

What is person-time?

Answer 3

The number of years a person is exposed to a risk.

Question 4

What is incidence and how can you calculate incidence rate?

Answer 4

Incidence = the number of new cases

Incidence rate = number of people with disease/number of people at risk x 100,00 (to get the rate in 100,000) people

Question 5

Define prevalence?

Answer 5

-Proportion of population that has a disease

Question 6

How can you calculate point prevalence rate and period prevalence rate?

Answer 6

Point prevalence rate = number of people with disease at a point of time/ Total number of people in the group x 100

Period prevalence rate = number of people with a disease over a period of time/average number of people in the group x 100

Question 7

What are the differences between incidence and prevalence?

Answer 7

Incidence is a rate or a proportion, it is useful for identifying the cause of disease.
Prevalence is a proportion and identifies disease burden.

Question 8

Define sporadic

Answer 8

Occasional cases occurring irregularly

Question 9

Define endemic

Answer 9

Persistent background level of occurrence

Question 10

Define epidemic

Answer 10

Occurrence in excess of the expected level for a given time period

Question 11

Define pandemic

Answer 11

Epidemic occurring or spreading over more than one continent

Question 12

What can different types of outcomes be?

Answer 12

Death,
Hospitalisation,
Diagnosis,
Relapse,
Difference in quality of life,
Surrogates (changes in blood pressure or lung function)

Question 13

What can different exposures be? (factors that lead to an outcome)

Answer 13

Non-modifiable - age and genotype.
Modifiable - smoking, weight, exercise, diet, alcohol consumption.
Interventions - Drugs, surgery and lifestyle advice

Question 14

What is risk?

Answer 14

The percentage of the number of outcomes in a group/number of people in the group

Question 15

what is relative risk?

Answer 15

The ration of the people exposed to the people unexposed

Question 16

What is relative risk reduction?

Answer 16

(1-relative risk) x 100

Question 17

What is the absoloute risk reduction?

Answer 17

Risk in unexposed - risk in exposed

Question 18

What is the number needed to treat?

Answer 18

1/absolute risk reduction

Question 19

What is a confidence interval?

Answer 19

They represent the range of plausible values. Wider the intervals, the greater the uncertainty. So this makes them very useful in appraising published research.

Question 20

Describe the hierarchy of evidence

Answer 20

It ranges from the most reliable sources (systematic reviews and meta-analysis), then experimental designs, quasi-experimental designs, then observational-analytic designs and observational descriptive designs. To the least reliable (background information and expert opinion)

Question 21

What is a cross-sectional study?

Answer 21

Looks at the different; exposures, signs/symptoms and outcomes. The data can be used to look at prevalence and associations

Question 22

What is a case-control study?

Answer 22

This samples cases with outcomes and without outcomes. It explores and compares exposures and helps identify associations (looking at cause)

Question 23

What is a cohort study?

Answer 23

It compares the risk of the disease in the unexposed and exposed and looks at the cause, prognosis and incidence.

Question 24

What is a randomised controlled trial?

Answer 24

It uses the randomised use of intervention and controls. It is used to compare the risk of outcome in intervention and control groups

Question 25

What are the different study designs good for?

Answer 25

Randomised controlled trial - looks at treatment effect
Cohort - looks at cause, prognosis and incidence
Case controlled - cause
Cross sectional - prevelence.