Abstract

RUANO-RAVINA, Alberto; PEREZ-RIOS, Mónica  and  BARROS-DIOS, Juan Miguel. Population-based versus hospital-based controls: are they comparable?. Gac Sanit [online]. 2008, vol.22, n.6, pp.609-613. ISSN 0213-9111.

Objective: To compare whether there are differences among hospital and population controls. Methods: Two case-control studies were conducted on lung cancer risk factors in the Santiago de Compostela Public Health District. Whereas one used randomly chosen census-based population controls, the other used consecutive hospital controls that went to the reference hospital for non-smoking-related trivial interventions. The differences were analyzed using logistic regression. The dependent variable was type of control (hospital or population). Results: Hospital controls had a similar tobacco habit than population controls, but consumed more alcohol. For those consuming more than 50 ml daily, the risk of being a hospital control was 4.83 (95%CI: 2.55-9.14). Conclusions: There may be some differences between hospital and population-based controls, which must be taken into account in the design of case-control studies. It is necessary to ascertain whether such differences are reproduced at other geographic locations and whether they can affect estimation of exposure-disease.

Keywords : Epidemiologic studies; Case-control studies; Retrospective studies; Selection bias; Tobacco; Alcohol.

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