Atrial fibrillation makes the heart beat irregularly. One of the main risks of atrial fibrillation is that it increases the risk of stroke. There is good evidence that blood thinning medications reduce the risk of stroke, however, these medications can also increase the risk of bleeding. Warfarin was the only oral blood thinner available, but in the last 10 years, another four medications have entered the market and their use has increased rapidly. These new blood thinners are called direct oral anticoagulants or DOACs. Clinical trials have shown that DOACs are as effective as warfarin for preventing stroke and they may also be associated with a lower bleeding risk. However, older people, particularly those who have other illnesses such as dementia, were excluded from the trials so we are unsure whether the results can be applied to this group of people. The aim of this study is to look at how DOACs and warfarin are being prescribed to older people in the community and investigate whether the DOACs are as effective as warfarin for stroke prevention and as safe with respect to bleeding. This information will help prescribers to decide which type of blood thinner is most appropriate for older patients.
This study will describe the prescribing of oral anticoagulants to people over the age of 75 for the treatment of atrial fibrillation (AF) and investigate whether the newly introduced direct oral anticoagulants (DOACs) are as effective and safe as warfarin, which has been used for decades. Initially an explorative study will be conducted to review whether the characteristics of older people prescribed anticoagulants have changed since the introduction of DOACs. Cohort studies will then be used to investigate serious outcomes including ischaemic stroke, bleeding (major and clinically relevant), intracranial haemorrhage, gastrointestinal haemorrhage, myocardial infarction and mortality. Two comparator warfarin groups (one contemporary and one historical) will be used to evaluate the effect of channelling. People prescribed DOACs will be matched by age, sex, GP practice and index year to people prescribed warfarin during the same period or during a historical period before DOACs became available. Time to diagnosis of these outcomes will be compared using survival analysis. Covariates including smoking, alcohol, BMI, comorbidities and co-prescribing will be adjusted for. Renal impairment, body-weight, frailty, falls, co-morbidities, and polypharmacy may influence the safety of DOACs in older people with AF. This will be investigated using the regression model.
Ischaemic stroke; Composite of all bleeding; Major bleeding; Gastrointestinal bleeding; Clinically significant non-major bleeding; Myocardial infarction; All-cause mortality; Intracranial haemorrhage.
Anita McGrogan - Chief Investigator - University of Bath
Anneka Mitchell - Corresponding Applicant - University of Bath
Julia Snowball - Collaborator - University of Bath
Margaret C Watson - Collaborator - University of Bath
Tomas Welsh - Collaborator - University of Bristol