In a study in UK, an association was found between sale of antiasthma drug and an increase in deaths due to asthma. This is an example of
A. Ecological study
B. Cohort study
C. Case reference study
D. Experimental study
(Modified repeat question – AIIMS Nov 06 – AA q46 – Original question was about anti arrhythmia drug)
Correct answer: A. Ecological study
An ecological study is an epidemiological study in which the unit of analysis is a population rather than an individual. For instance, an ecological study may look at the association between smoking and lung cancer deaths in different countries. An ecological study is normally regarded as inferior to non-ecological designs such as cohort and case-control studies.