Frequency Of Disease

Question 1

What is prevalence?

Answer 1

The proportion of people with a disease or condition in a given population at a specified time

Question 2

What are the different types of prevalence?

Answer 2

Point prevalence

Period prevalence

Question 3

What is point prevalence ?

Answer 3

Prevalence and data which has been collected at a single point in time

Question 4

What is period prevalence?

Answer 4

Prevalence and data that has been collect of a period of time-less commonly used

Question 5

What may a high and low prevalence reflect?

Answer 5

High prevalence - high risk population, prolonged survival without cure

Low prevalence - low risk population, rapid cure

Question 6

What does incidence mean?

Answer 6

The number of new cases of a disease or condition that occur in a given population over a specified period of time
-indicates risk

Question 7

What is a population ?

Answer 7

A group of people with a common characteristic

E.g a place, time, age, gender, occurrence of a life event

Question 8

What are the 2 types of membership ?

Answer 8

Permanent membership

Transient membership

Question 9

What is a population with a permanent membership ?

Answer 9

A population with a permanent membership is ‘fixed’ or ‘closed’
-e.g people who lived in Stoke on the 1st of January 2017

Question 10

What is a population with a transient membership?

Answer 10

A population with a transient membership is ‘dynamic’ or ‘open’
-e.g the population of Stoke

Question 11

What is the most common measure of frequency?

Answer 11

Count

-often expressed as an integer (number of people with the disease)

Question 12

How is ratio calculated ?

Answer 12

One number dived by another ( x/y )

Question 13

How is proportion calculated ?

Answer 13

Number dived by all ( x/ x+y )

-often expressed as a percentage

Question 14

How is rate of disease calculated ?

Answer 14

Cases divided by total population x time ( x/x+y times 1/t )

E.g 1 out of 50 women per year

Question 15

What are the benefits of estimation of prevalence?

Answer 15

Determine of sickness load
Planning health services
Examining health behaviours

Question 16

What are the 2 types of incidence ?

Answer 16

Incidence proportion

Incidence rate

Question 17

What is incidence proportion?

Answer 17

The proportion of people who develop a disease during a specific period of time
-cases per population

Question 18

What is incidence rate ?

Answer 18

The rate at which people develop a new disease during a specific period of time
-cases divided by person time ( cases per person per year )

Question 19

How do you calculate person time?

Answer 19

Sum of the total time contributed by all subjects

-the time a person is not infected for

Question 20

What is case fatality rate?

Answer 20

Proportion of cases of a particular disease who die during a specific time period

Question 21

What is crude mortality rate?

Answer 21

Proportion of people that die in a population during a specific time period
-Number of deaths divided by total population

Question 22

What is an ecological study ?

Answer 22

A study in which the unit of analysis is the population and not the individual
E.g different countries, different ethnic groups

Question 23

What are the strengths and weaknesses of an ecological study ?

Answer 23

Strengths: simple and cheap, good at hypothesis generating, assess outcomes on a population rather than the individual level

Weaknesses: potential for ecological fallacy (making wrong assumptions on an individual based on a population ) , misses possible effects in small subgroups

Question 24

What is a cross sectional study?

Answer 24

A snapshot of health at an individual period of time

E.g prevalence of smoking in adult population in 1948

Question 25

What are the strengths and weaknesses of cross sectional survey?

Answer 25

Strengths : quick and inexpensive, useful for estimating size of problem, potential for a large population size if data collection method is simple

Weaknesses: tendency to selectively include problems with long duration, susceptible to non-response bias (doesn’t include those who don’t respond)

Question 26

What is a case control study?

Answer 26

A type of study in which two existing groups differing in outcome are identified and compared on the basis of some casual attribute
E.g people with lung cancer compared to people without lung cancer but are similar in every other factor
-look back at the hypothetical cause of the disease

Question 27

What are advantage of case controls ?

Answer 27

Useful for rare outcomes, they can be done quickly, useful for outcomes in which there is a long period since exposure

Question 28

What are the disadvantages of case controls ?

Answer 28

Only one outcome is assessed so are highly specific to a disease, measurement of exposure is often wrong or inaccurate (has bias)

Question 29

What is a cohort study?

Answer 29

Like a cross sectional study but is across time

-look at the exposed and non exposed and the outcomes of interest

Question 30

What are the advantages and disadvantages of cohort studies ?

Answer 30

Advantages: investigators multiple outcomes, minimise recall bias ( more frequent questionnaires),

Disadvantages: expensive and time consuming, inefficient for rare outcome, potential selection bias (people drop out etc)

Question 31

What is an intervention study ( like a random clinical trail )?

Answer 31

Used to determine the effectiveness of an intervention like a drug/treatment
-give some the drug and some a placebo (determine that with non bias-randomised) Single or double blinded trails

Question 32

What are the advantages and disadvantages of a random clinical trial?

Answer 32

Advantages: best method for evaluating effectiveness of drug, bias minimised, explains cause and effect

Disadvantages: difficult, time consuming and expensive, ethical restrictions, non-compliance of controls threatens validity

Question 33

What is the difference between primary and secondary data?

Answer 33

Primary- collected first hand by the investigator for a specific purpose

Secondary- data has already been collected, and is used by someone else for a different purpose

Question 34

What is ecological fallacy?

Answer 34

The error of making inferences about individual behaviour from aggregate data

Question 35

A longitudinal or prospective study is also referred to as what study?

Answer 35

A cohort study