Selection bias in occupational case-control studies that use death registries to select subjects: A discussion and demonstration

Authors

  • Dr. Murray M. Finkelstein PhD, MDCM,

    Corresponding author
    1. Health Studies Service, Ontario Ministry of Labour, Toronto, Ontario, Canada
    • Health Studies Service, Special Studies and Services Branch, Ontario Minstry of Labour, 400 University Avenue, 8th Floor, Toronto, Ontario, Canada M7A 1T7
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  • Gary M. Liss MD, MS, FRCP (C)

    1. Health Studies Service, Ontario Ministry of Labour, Toronto, Ontario, Canada
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Abstract

Some epidemiologic studies have selected subjects from death registries. This method is, however, subject to substantial systematic bias that arises from the fact that different segments of society have different risks of death in any year. Different occupational groups will thus have unequal probabilities of entering the pool of potential controls, and biased estimates of the odds ratios that relate occupation to disease will result. Failure to recognize the bias may lead to invalid conclusions. This selection bias is discussed, with particular reference to studies of malignancies among farmers. The bias is demonstrated by using data from studies of Parkinson's disease and sinonasal cancer.

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