Epidemiological Study Design
Epidemiological studies classified based on distribution of disease:
- Descriptive Epidemiological study:
Describe the distribution of disease or condition in human population
Eg.distribution of certain condition or disease in a certain population in relation to age, sex or other characteristics
- Analytical Epidemiological Study:
These studies Test the hypothesis.
Looks for association based on;
- Groups or individuals eg: Correlation study, trend study
- Based on individuals eg: Cross – sectional, cohort, case control study
Cohort Study: Identification of individual forming a group with certain exposure and the group is followed up in time to ascertain the disease occurrence.
Case Control Study: Case control study directed at the prior exposure of the disease, which caused the disease and thus proceed from effect to cause.
Cross Sectional Study: The study is conducted to collect data on both exposure and outcome individuals of study population.
Epidemiological Studies classified based on the role and control of investigator on the study:
- Observational Study: Investigator observes the occurrence of condition or disease in population with certain exposure. These studies are most feasible and practical to conduct.
- Experimental Study: Investigator controls the assignment of exposure, associated factors and observation of the outcome. These are robust study design to test hypothesis.
Epidemiological studies classified based on direction of investigation.
- Prospective study: Population exposed or non exposed to disease are followed up and compared with the respect to subsequent development of disease or the outcome of the study.
- Retrospective study: Populations with exposed or non exposed disease are compared to determine whether they differ in past exposure to the causative factor which is the study hypothesis.
- Ambispective study: Study is both retrospective and prospective. One or more variable are measured retrospective and the other one retrospective, or variables primary variable is measured both retrospective and prospectively.
- Non – Directional study: Investigator observes exposure and disease status simultaneously in a study population.
- Retrolective study: Data collected before the study design, not necessarily for the study purpose.
- Prolective study: Data collected after study design for the study purpose.