Question

State one of the most important ways in which ecologic studies differ from other observational study designs used in epidemiology. What is meant by the ecologic fallacy?

Using your own ideas, suggest a possible design for an ecologic study; how might the study design be affected by the ecologic fallacy?

Answer 1

Epidemiogy is the study of the distribution and determinants of health related states or events in specified populations and the application of this study to the control of the health problems.

Ecological studies are studies of risk modifying factors on health or other outcomes based on population defined either geographically or temporarily. Studies that use group of people as a unit of study is called as ecological studies.

Observational studies are the studies , in this the investigators observe the study withou any intervention or manipulation. Other observational studies : cohort study, case control study

1. Cohort study : individuals defined according to exposure , followed for disease
2. Case control study: individuals defined according to disease, exposures compared

Ecological studies: population defined accprding to exposure and disease at a single time point. These are the difference between other observational studies.

ECOLOGICAL FALLACY : a type of logical error which occurs when relationships which exist at the group level are incorrectly assumed to hold at the individual level.

For example : the US immigrants from Japan have same rates of disease of US whites , but they are much lower than japanese residents. The differenca may be due to , the life style , environmental factors during adulthood. The interpretation of the studies limited to difference between countries in the classification and detection of disease or cause of death