Influence of design characteristics on the outcome of retrospective cohort studies

Retrospective cohort studies are increasingly being applied in occupational health. To describe and investigate further this type of study 179 retrospective cohort studies published in six scientific journals between 1975 and 1985 inclusive were reviewed. A description of the 179 reviewed articles was made and relations between investigator orientated variables, design characteristics, and the outcome of the study were investigated. Retrospective cohort studies focusing on exposures in the chemical industry appeared to yield most negative findings, which is partly explained by the relation between the affiliation of the investigator and the outcome of the study. Studies requiring a minimal latency period, an occupational reference group, and a low percentage of lost to follow up tended to have a higher chance of a positive finding. Study size, however, did not appear to be related to the outcome.