Overcoming the reluctance to prescribe anticoagulants in older people with AF

Anticoagulants have consistently been shown to reduce the risk of stroke for people with atrial fibrillation, but there may be a reluctance to prescribe these medications to older people due to concerns around adverse events and bleeding. Anneka Mitchell PhD, lead pharmacist for healthcare of older people and frailty at University Hospitals Plymouth NHS Trust and visiting postdoctoral researcher at the University of Bath, discusses recent research into the risks of stopping anticoagulation in this group.

Warfarin has been used for decades for stroke prevention in atrial fibrillation (AF) and there is good evidence that efficacy is maintained in older people and the benefits outweigh the risks for most patients.¹

Warfarin has historically been underused in older patients² due to the need for frequent blood tests and variable dosing schedules, which can make it difficult for people with cognitive impairment to take the correct dose. What’s more, the numerous medication and food interactions can lead to over- or under-dosing.

The direct oral anticoagulants (DOACs) dabigatran, rivaroxaban, apixaban and edoxaban have now largely superseded warfarin and other vitamin K antagonists as the anticoagulants of choice due to their comparable efficacy and lower risk of adverse events.^3–6 They are now recommended as the first-line option for most patients in UK and European guidelines.^7,8

A reluctance to prescribe anticoagulants

Despite having safer options available, anticoagulants are often still under-prescribed to older patients, particularly those felt to be high risk of bleeding, such as those with a history of falls or those living with frailty.⁹

Guidelines have specifically advised that anticoagulation should not be withheld due to falls for over 10 years,^7,10 as it has been estimated that an older person taking warfarin would need to fall at least 295 times in a year for the risk of bleeding to outweigh the benefit of stroke prevention.¹¹ More recent work has suggested that an older person taking rivaroxaban would need to fall 45 times in a year, and for apixaban they would need to fall 458 times per year to have a lower net clinical benefit than aspirin.¹²

It is not known why clinicians still choose to withhold anticoagulation in patients who fall. It has been hypothesised that prescribers are more fearful of acts of commission, such as causing a fatal intracranial bleed by prescribing an anticoagulant to a patient known to fall, than they are of an act of omission, such as causing a stroke due to not prescribing anticoagulation to the same patient.¹³

For people living with frailty, there is often a shift toward deprescribing with less focus on prevention and more on active symptom management. Information on when to stop anticoagulation for AF is not readily available, so these decisions are person-centred and can also be influenced by individual clinicians’ perceptions of the risks and benefits of these medications.

Risks of stopping anticoagulants for older people with AF

Our study, published recently in the journal Heart,¹⁴ used routinely collected healthcare data from UK primary care to evaluate effectiveness (stroke reduction) and safety outcomes (bleeding, myocardial infarction and death) in people aged 75 years and over by attributing the event to their anticoagulant exposure status at the time of the event.

All patients entered the study cohort on the date of their first anticoagulant prescription for AF. We then estimated their anticoagulation exposure over time using data from prescription records and recorded time spent exposed to an anticoagulant (warfarin, apixaban or rivaroxaban) and time spent unexposed.

Over 20,000 patients contributed data to the cohort, and we found that in this large sample, non-exposure to anticoagulants was associated with up to a three-fold increase in the risk of stroke and death, and a two-fold increase in the risk of myocardial infarction compared with being exposed to one of the anticoagulants.

There was no evidence for a reduction in major bleeds during unexposed time, but minor bleeds were reduced.

We hypothesised that the increased risk of death in unexposed time may have been due to medication being stopped for end-of-life care. However, there was no evidence in our data to support this.

Similar findings have been observed in other studies using different data from the UK and Denmark. García Rodriguez et al¹⁵ found that in 616 incident cases in the UK and 643 cases in the Region of Southern Denmark, patients with AF who had discontinued oral anticoagulation had a two- to three-fold higher risk of ischaemic stroke.

In their Global Anticoagulant Registry in the Field-Atrial Fibrillation study,¹⁶ Cools et al found that the rate of anticoagulant discontinuation was 13%. Discontinuation for seven or more consecutive days was associated with significantly higher all-cause mortality and risks of stroke and myocardial infarction.

Conclusions

The increased risk of serious events when anticoagulation is withheld or discontinued in older patients is concerning, and this should be considered when deciding whether to start or stop an anticoagulant for an older person with AF.

Addressing modifiable risk factors for stroke and bleeding, such as smoking, alcohol consumption and blood pressure control, may make anticoagulation safer and also reduce stroke risk independent of treatment.

There is a need to focus not only on comparing different anticoagulant strategies to ensure the safest and most effective treatments are used, but also to examine the risks of deprescribing anticoagulants so that the risks of doing so can be adequately discussed with patients before coming to a shared treatment decision.¹⁴ This article was originally published by our sister publication Hospital Pharmacy Europe.

Author

Anneka Mitchell PhD Lead pharmacist healthcare of older people, frailty and medicine, University Hospital Plymouth NHS Trust, Plymouth, UK and visiting postdoctoral researcher, University of Bath, UK

Acknowledgements

With thanks to fellow study authors:

Margaret C Watson Professor of health services research and pharmacy practice, Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, UK

Tomas J Welsh Academic geriatrician and ReMind UK research and medical director, The ReMind UK Centre, Royal United Hospital Bath NHS Trust, UK

Anita McGrogan Senior lecturer/associate professor, University of Bath, UK

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