Introduction to Epidemiology

Question 1

Define epidemiology

Answer 1

Epidemiology = study of distribution and determinant of disease or health outcomes in specified populations and the application of this study to the control of health problems.

Question 2

Uses of epidemiology

Answer 2

Causation, Natural history, description of health status of populations, evaluation of intervention.

Question 3

• Determinants of disease

Answer 3

Biologic, Lifestyle/behavior, Environmental (Social/Physical), Healthcare delivery system

Question 4

Why measure populations

Answer 4

• to investigate the burden of disease
• understand causes and prognosis of disease
• evaluate interventions to treat and prevent disease

Question 5

Describe main sources of demographic information available in the UK

Answer 5

UK census - held every 10 years. complete a form = paper/online.
information provided= household, individual. aggregated by lower middle or upper super output areas

Question 6

Advantages of UK census

Answer 6

• comprehensive
• technically everyone should be included in the form
• wide range of data

Question 7

Disadvantages of UK census

Answer 7

completeness - does not include everyone, some misleading resonses, questionable questions, massively expensive, quickly out of date.

Question 8

Current population =

Answer 8

census population + births - deaths

Question 9

Define rate =

Answer 9

= number of cases / population

Question 10

Define Crude birth rate

Answer 10

Number of live births to residents of an area in one year per 1000 population of that area (population present at the mid year)

Question 11

Define General fertility rate Number of live births to an area’s residents in one year per 1000 female population aged 15-44 years in that area

Answer 11

Number of live births to an area’s residents in one year per 1000 female population aged 15-44 years in that area

Question 12

Define Age-specific fertility rate Number of live births in one year per 1000 population within a particular age band

Answer 12

Age-specific fertility rate Number of live births in one year per 1000 population within a particular age band

Question 13

Define Total period fertility rate

Answer 13

Total period fertility rate Average number of children per woman based on current fertility rates

Question 14

Define crude mortality rate

Answer 14

=number of deaths in the population / mid-year population

Question 15

Define infant mortality rate

Answer 15

=number of deaths under 1 year old / number of live births

Question 16

crude mortality rates depend upon

Answer 16

the age specific rates and the population in each of the age bands

Question 17

• Direct age standardisation applies the age specific rates of populations one wants to compare to a single “standard population”.

Answer 17

Allows for a fairer comparison between different populations.

Question 18

Define Prevalence =

Answer 18

proportion of a population living with a specific health outcome within a specified time // existing cases of disease

Question 19

Describe the two types of prevalence

Answer 19

• Point prevalence = prevalent cases / average population at a specific point in time
• Period prevalence = prevalent cases /average population over a range of time

Question 20

Define incidence

Answer 20

= All individual cases who change in status from non-disease to disease – or from one state of a health outcome to another – over a specific period of time // occurrence of new cases

Question 21

Define Risk

Answer 21

• proportion of an at-risk population that develops a specific health outcome within a specified amount of time

Question 22

Risk =

Answer 22

number of incident cases / total number of at risk individuals

Question 23

Define rate

Answer 23

the frequency of incident cases per unit of person-time

Question 24

Incidence/Prevalence Relationship

P = I*D

Answer 24

• Quickly fatal diseases/recoverable diseases = high incidence, low prevalence
• Chronic diseases = high prevalence, low incidence

Question 25

Sources of Data

Answer 25

• Disease registers (e.g. cancer registries)
• GP “spotter” practices
• Special prevalence surveys (e.g. Health Survey for England)
• Disease notifications (for notifiable diseases)
• Hospital episode statistics

Question 26

SUMMARY

Answer 26

Incident cases = NEW cases

Prevalent cases = ALL cases