Ecological study (epidemiology)

An ecological study is a type of epidemiological study based on the population as the unit of study, in which information is lacking on the relationship in the individual between the exposure factor and the disease in the population in study.

Types of ecological studies

1. Exploratory ecological study.
2. Study with emigrants.
3. Ecological comparison study.
4. Ecological trend study.
5. Mixed ecological study

Advantages of an ecological study

1. They are relatively cheap and feasible, especially with secondary data obtained from population databases. It is useful to select new hypothesis.
2. It is useful to assess the effectiveness of health programmes, interventions and policies in the population, especially when the effects on the individual (effectiveness) are not tested, but are known for previous research.
3. Sometimes they serve to identify certain types of effects that are not detected in the individual.

Disadvantages of an ecological study

1. Ecological fallacy: Because A groups are not fully homogeneous with respect to the state of exposure, the realization of causal inferences is limited by the association that is performed in the group more than in the individual, that is A it is not correct to extrapolate data from the population to the individual, by the design of this study.
2. Multicolinearity: It is difficult to separate observed effects from two or more exposures.
3. Many A data are not available when added to the population.
4. Temporary ambiguity: Often it is not possible to determine whether the exposure precedes the disease.
5. In trend studies it is difficult to separate the influences of changes in a short time interval from the influences of a large time interval.