Introduction to Epidemiology Flashcards
Define epidemiology
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.
Uses of epidemiology
Causation, Natural history, description of health status of populations, evaluation of intervention.
• Determinants of disease
Biologic, Lifestyle/behavior, Environmental (Social/Physical), Healthcare delivery system
Why measure populations
- to investigate the burden of disease
- understand causes and prognosis of disease
- evaluate interventions to treat and prevent disease
Describe main sources of demographic information available in the UK
UK census - held every 10 years. complete a form = paper/online.
information provided= household, individual. aggregated by lower middle or upper super output areas
Advantages of UK census
- comprehensive
- technically everyone should be included in the form
- wide range of data
Disadvantages of UK census
completeness - does not include everyone, some misleading resonses, questionable questions, massively expensive, quickly out of date.
Current population =
census population + births - deaths
Define rate =
= number of cases / population
Define Crude birth rate
Number of live births to residents of an area in one year per 1000 population of that area (population present at the mid year)
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
Number of live births to an area’s residents in one year per 1000 female population aged 15-44 years in that area
Define Age-specific fertility rate Number of live births in one year per 1000 population within a particular age band
Age-specific fertility rate Number of live births in one year per 1000 population within a particular age band
Define Total period fertility rate
Total period fertility rate Average number of children per woman based on current fertility rates
Define crude mortality rate
=number of deaths in the population / mid-year population
Define infant mortality rate
=number of deaths under 1 year old / number of live births
crude mortality rates depend upon
the age specific rates and the population in each of the age bands
• Direct age standardisation applies the age specific rates of populations one wants to compare to a single “standard population”.
Allows for a fairer comparison between different populations.
Define Prevalence =
proportion of a population living with a specific health outcome within a specified time // existing cases of disease
Describe the two types of prevalence
- Point prevalence = prevalent cases / average population at a specific point in time
- Period prevalence = prevalent cases /average population over a range of time
Define incidence
= 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
Define Risk
- proportion of an at-risk population that develops a specific health outcome within a specified amount of time
Risk =
number of incident cases / total number of at risk individuals
Define rate
the frequency of incident cases per unit of person-time
Incidence/Prevalence Relationship
P = I*D
- Quickly fatal diseases/recoverable diseases = high incidence, low prevalence
- Chronic diseases = high prevalence, low incidence
Sources of Data
- 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
SUMMARY
Incident cases = NEW cases
Prevalent cases = ALL cases
