Study population
From the base cohort (see above)
we restricted the dataset to patients with at least two INR
measurements, at least one recorded vitamin K antagonist (VKA)
dispensing, and at least one statin dispensing. Within this cohort we
identified all incident prescriptions for simvastatin, atorvastatin and
rosuvastatin, defined as a prescription with no preceding prescription
for a statin within the last 2 years. If one individual had two such
incident prescriptions for the same statin, only the first was included.
We further restricted to those with at least one INR measurement 8 weeks
before statin initiation, as well as at least one INR measurement within
12 weeks after statin initiation. Finally, we excluded those with no VKA
prescription within 8 weeks before statin initiation and those aged
<18 years at the time of statin initiation.