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Selection bias due to immigration in pharmacoepidemiologic studies
1Research Unit of General Practice, University of Southern Denmark, Denmark. hstovring@health.sdu.dk
Pharmacoepidemiology and Drug Safety
|April 26, 2007
Summary
Selection bias from excluding recent immigrants in antidiabetic drug studies is minimal, especially when accounting for age and sex. The waiting time distribution (WTD) method is a valuable tool for assessing this bias.
Area of Science:
- Pharmacoepidemiology
- Health Services Research
Background:
- Prevalence studies often exclude recent immigrants, potentially introducing selection bias.
- Understanding this bias is crucial for accurate estimations of antidiabetic drug use.
Purpose of the Study:
- To quantify selection bias in antidiabetic drug use prevalence due to excluding recent immigrants.
- To compare the efficacy of the waiting time distribution (WTD) method versus traditional run-in periods for bias assessment.
Main Methods:
- Utilized data on antidiabetic drug redemptions from 1992-2003 for ~470,000 individuals.
- Compared prevalence estimates derived from a run-in period with those from the WTD approach.
- Assessed bias by comparing non-immigrant estimates to the entire population using WTD.
Main Results:
- The WTD method showed immigrant antidiabetic drug prevalence was approximately half that of non-immigrants.
- This resulted in a small annual relative bias (0.73%-1.36%) when comparing non-immigrants to the total population.
- Bias diminished upon stratification by age and sex, except in individuals under 40.
Conclusions:
- Selection bias due to immigration in antidiabetic drug prevalence studies is minor after adjusting for age and sex.
- The WTD approach is effective for evaluating selection bias and may be preferable to run-in periods.
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