A total of 850 insulation workers employed between 1940 and 1945 was identified from the personnel records of three large insulation manufacturing plants in the Midwestern U.S. in 1980. During the period 1940-1980, 28 deaths from lung cancer were discovered among the workers. Only eight lung cancer deaths, however, were reported among a comparable group of 800 coworkers who did not work with insulation during the same time period. The investigators had hypothesized that exposure to the insulation material increases the risk of lung cancer.

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Which epidemiology study design best represents this description?

A Retrospective cohort study is a type of observational study or research. The investigator looks back in time self-report data to see if the risk of disease was different between exposed and non-exposed patients.

The distinguishing feature, that help in identifying it, of this study is that the investigators conceive the study and begin identifying subjects after results have already been found or developed in some of the subjects.