Demographic studies :

1. Focus on the occurrence of disease in populations; Vs. those epidemiologic studies which concentrate on the occurrence of disease among individuals in relation to possible risk factors;

2. Search for associations between disease frequency and the presence or absence of possible etiologic agents in those populations;

3. Address issues as to whether a disease is increasing or decreasing in the population, and whether a disease occurs more often in populations that have greater exposure to a potential cause.