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The effect of using different reference dates for control exposure measurement on relative risk estimates in a
A H Rampey1, K L Irwin, M W Oberle
1Lilly Research Laboratories, Lilly Corporate Center, Indianapolis, IN 46285.
Journal of Clinical Epidemiology
|May 1, 1993
Summary
Choosing a reference date for time-dependent exposures in case-control studies with non-identical enrollment periods had minimal impact on odds ratios in this cervical cancer study. Careful consideration of reference dates is still advised.
Area of Science:
- Epidemiology
- Reproductive Health
- Oncology
Background:
- Case-control studies are crucial for investigating disease etiology.
- Time-dependent exposures require careful measurement, especially when enrollment periods differ.
- Oral contraceptive (OC) use is a known risk factor for cervical cancer.
Purpose of the Study:
- To evaluate the impact of different reference dates on odds ratios in a case-control study.
- To assess the sensitivity of results to the choice of reference date for time-dependent variables.
- To provide guidance on selecting reference dates in epidemiological research.
Main Methods:
- Utilized data from a case-control study on cervical cancer and oral contraceptive (OC) use.
- Compared odds ratios derived from five distinct reference dates for determining control exposure status.
- Analyzed a scenario where control enrollment began 6 months after case enrollment concluded.
Main Results:
- The selection of the reference date demonstrated a minimal effect on the calculated odds ratios.
- Results indicate robustness of the association between OC use and cervical cancer to reference date variations in this specific study.
- The chosen reference dates did not significantly alter the study's main conclusions regarding OC use and cervical cancer risk.
Conclusions:
- The choice of reference date for time-dependent exposures had little impact on odds ratios in this cervical cancer case-control study.
- Findings suggest that while the impact may be minimal in some scenarios, careful consideration of reference dates is essential.
- Methodological rigor in defining reference points is crucial for valid epidemiological research, particularly when enrollment periods are asynchronous.
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