Related Experiment Video
Updated: Jun 27, 2026

Drug Repurposing Hypothesis Generation Using the "RE:fine Drugs" System
Published on: December 11, 2016
Drug exposure risk windows and unexposed comparator groups for cohort studies in pharmacoepidemiology
A D McMahon1, J M Evans, M M McGilchrist
1Department of Clinical Pharmacology, University of Dundee, Scotland, UK. alex@memo.dundee.ac.uk
Aim:
To determine the appropriate size of risk windows in both exposed and unexposed sub-cohorts.
Method:
Data was taken from a previous study of upper gastrointestinal haemorrhage and perforation. The length of each prescription for NSAIDs was estimated. The risk was calculated for the duration of a prescription plus increments of -30, -25,..., +115, +120 (i.e. 31 increments). Ten unexposed groups were re-sampled for each increment (stratified for age and sex), using the same lengths of risk window as the exposed group. Mean risks and rate-ratios were calculated (per thousand person-years).
Results:
The NSAID risk rose from 3.52 at -30 days to a peak of 5.82 at -15 days, and then decreased gradually to 2.83 at +120 days. Unexposed risk was variable for the negative increments, and decreased gradually from 2.16 at +0 days to 1.54 at +120 days. The rate-ratio rose from 1.55 at -30 days to a peak of 2.85 at -5 days, and then decreased to 1.85 at +120 days.
Conclusion:
Risk windows should be the same as (or slightly less than) the calculated length of a prescription. Lengthy windows should not be used for unexposed comparator groups (the exposed windows may be randomly allocated).
More Related Videos
Related Concept Videos
Analysis of Population Pharmacokinetic Data
Types of Biopharmaceutical Studies: Controlled and Non-Controlled Approaches
Non-controlled studies, commonly employed for initial exploration, lack a control group, rendering them susceptible to biases and external influences. In contrast, controlled...
Dosage Regimens: Partial Pharmacokinetic Parameters
Pharmacokinetic–Pharmacodynamic Relationship: Exposure, Response and Effect
Study Designs in Epidemiology
Observational studies are those where the researcher does not intervene but rather observes natural variations. They include cross-sectional, cohort, and case-control studies.
Comparing the Survival Analysis of Two or More Groups

