JAMAevidence JAMA Guide to Statistics and Methods Immortal Time Bias in Observational Studies With Dr Kabir Yadav
Jan 4, 2024
Dr Kabir Yadav, Statistical Editor, discusses immortal time bias in observational studies with Dr Roger Lewis. They explore the misclassification of immortal time in observational studies compared to randomized trials, address the bias in the UK Biobank study, and examine the higher risk of cardiovascular events in women with premature menopause.
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RCTs and Immortal Time Bias
- In randomized controlled trials (RCTs), immortal time bias isn't a problem.
- The common starting point for measuring time to events eliminates unexplained time intervals.
COPD Example
- Consider preventing adverse events in COPD patients post-discharge.
- In observational studies, there's a gap between discharge and treatment start, creating immortal time.
Classifying Time Intervals
- Time between discharge and medication pickup should be considered unexposed time.
- Treatment time should begin only when the patient starts taking medication.