Key words: population, disease frequency, disease distribution, disease determinants, disease
Numerator (number of existing cases) /Denominator (total population)
2)determine the extent of disease in a population
3)identify patterns and trends in disease occurrence
4)identify the causes of disease
5)evaluate the effectiveness of measures that prevent and treat disease
Person, Place, Time.
2) Case Studies
3) Correlational Studies
4) Cross-sectional studies
Same group over different time periods.
What are the limitations?
Provide data on populations not individuals, cannot control for all differences among populations
POPULATION IS NOT SELECTED ON EXPOSURE OR DISEASE
Provide important data for public health planning
low cost! and generalizability!
No temporal sequence between exposure and disease
Assess prevalence of disease
i.e. crude death rates
Then obtain exposure history
***GOOD FOR RARE DISEASES**
The “What will happen to me?” study follows a group of healthy people with different levels of exposure and assesses what happens to their health over time.
Disease-free subjects selected and classified based on exposure, follow subjects through time.
Everything has happened already
Expensive, Take a long time, Require a large study size, Exposure can change
Costly, Time consuming