Key definitions
- Epidemiology: the study of the frequency, distribution and determinants of disease in populations
- Cause: an event, condition or characteristic that preceded the event/outcome without which the disease/outcome would not have occurred
- Risk factor: an attribute or exposure that is associated with increased probability of disease
- Mortality rates
- Crude death rates (whole population)
- (Number of live births per year/total midyear population) x 1000
- Age-specific mortality rates
- Cause-specific mortality rates
- Standardisation: permits comparison rate of mortality for populations with different age profiles
- Incidence rate: (number of NEW cases of a disease occurring in a population during a specific time period/number of persons exposed to the risk of developing the disease during that time period) x 1000
- Prevalence rate: (number of cases of a disease present in a population at a given time/number of persons at risk of the disease at that point in time) x 1000
| Incidence |
Prevalence |
Common/uncommon |
Duration |
Example |
| High |
Low |
Common |
Short |
Ebola |
| High |
High |
Common |
Long (chronic) |
Arthritis |
- Iceberg concept: people we know about (‘above water’) vs people we don’t (ill but not seeking help)
Population statistics
- P2 = P1 + births – (deaths + net migration)
- P2 = population size at any given period
- P1= population size at the start of the period