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Patient Evidence Summary
Doctor, I am overweight and I have atrial fibrillation. Is it safe for me to take one of the newer blood thinners instead of warfarin to prevent stroke?
Newer blood thinners (Direct Oral Anticoagulants; DOACs) have a lower risk of stroke and a lower risk of serious bleeding compared to warfarin for people with atrial fibrillation who have a normal Body Mass Index (BMI 19 to 25) or who are overweight (BMI 25 to 30). For people with a BMI over 30, the benefit from taking DOACs was similar compared to taking warfarin.
Study highlights
The quality of the included studies was high.
People taking standard doses of DOACs were less likely to have a stroke than people taking warfarin up to a BMI of 30. There was no difference between DOACs and warfarin for this outcome for people with BMI of 30 or higher.
People taking standard doses of DOACs were less likely to have serious bleeding events than people taking warfarin up to a BMI of 30. There was no diffference between DOACs and warfarin for this outcome for people with BMI of 30 or higher.
For people with a BMI above 40, standard doses of DOACs did not differ from warfarin at protection from stroke or reducing the risk of serious bleeding events. However, people taking warfarin in this group may have an unexplained lower risk of death due to other causes (not due to stroke or bleeding) compared to people taking DOACs.
The results were similar when patients were analyzed by body weight instead of BMI.
Understanding the problem
Being overweight or obese may result in a lower level of some drugs in the blood compared to people with a normal body weight. Warfarin, a drug used for stroke prevention due to atrial fibrillation for many decades, is known to be safe and effective in people who are overweight or obese. However, there has been concern that the blood level of DOACs in people who are overweight may be reduced. If this is true, taking DOACs could put these people at higher risk for having a stroke than if they took warfarin.
The reviewers wanted to know if the protective effect and safety of taking DOACs compared to warfarin for people with atrial fibrillation is different in people over a range of different BMIs.
A summary of the results from 4 studies published up to 2013.
Who? The studies included 57,866 people who had atrial fibrillation: 22,251 had class I obesity (BMI of 30 to 35) and 2,902 had class III obesity (BMI greater than or equal to 40).
What? The studies compared DOACs with warfarin.
Direct Oral Anticoagulants (DOACs) at standard doses | vs | Warfarin |
|---|---|---|
The standard dose for a DOAC depends on multiple factors and may change depending on the patient's age and other medical conditions. In this review, the most common doses are: Eliquis® (apixaban) - 5 mg twice a day Pradaxa® (dabigatran) - 150 mg twice a day Lixiana® (edoxaban) - 60 mg once a day Xarelto® (rivaroxaban) - 20 mg once a day | Warfarin at doses required to achieve an INR of 2.0 to 3.0. |
DOACs vs warfarin in people with a range of BMI who have atrial fibrillation
Outcomes at average of 26 months | BMI (kg/m2) | Rate of events with DOACs | Rate of events with warfarin | Results |
|---|---|---|---|---|
Stroke or systemic embolism | 25 to 30 (overweight) | 16 out of 1000 people per year | 19 out of 1000 people per year | Risk of stroke or systemic embolism was lower in people who took DOACs compared to people who took warfarin |
30 to 35 (class I obesity) | 14 out of 1000 people per year | 16 out of 1000 people per year | No difference between DOACs and warfarin* | |
40 or higher (class III obesity) | 8 out of 1000 people per year | 10 out of 1000 people per year | No difference between DOACs and warfarin* | |
| Major bleeding | 25 to 30 (overweight) | 28 out of 1000 people per year | 34 out of 1000 people per year | Risk of major bleeding was lower in people who took DOACs compared to people who took warfarin |
30 to 35 (class I obesity) | 31 out of 1000 people per year | 31 out of 1000 people per year | No difference between DOACs and warfarin* | |
40 or higher (class III obesity) | 31 out of 1000 people per year | 27 out of 1000 people per year | No difference between DOACs and warfarin* | |
| Death from any cause | 25 to 30 (overweight) | 35 out of 1000 people per year | 41 out of 1000 people per year | Risk of death was lower in people who took DOACs compared to people who took warfarin |
30 to 35 (class I obesity) | 33 out of 1000 people per year | 37 out of 1000 people per year | No difference between DOACs and warfarin* | |
40 or higher (class III obesity) | 39 out of 1000 people per year | 30 out of 1000 people per year | Risk of death was higher in people who took DOACs compared to people who took warfarin |
*Although the rates for the 2 groups look different, the differences were not statistically significant—this means that the difference could simply be due to chance rather than due to the different treatments.
This Evidence Summary is based on the following article:
Patel SM, Braunwald E, Steffel J, et al. Efficacy and Safety of Non-Vitamin-K Antagonist Oral Anticoagulants Versus Warfarin Across the Spectrum of Body Mass Index and Body Weight: An Individual Patient Data Meta-Analysis of 4 Randomized Clinical Trials of Patients With Atrial Fibrillation. Circulation. 2024 Mar 19;149(12):932-943. doi: 10.1161/CIRCULATIONAHA.123.066279. Epub 2024 Jan 24. PubMed
Lori-Ann Linkins, MD, MSc (Clin Epi), FRCPC
Dr. Linkins is an Associate Professor of Medicine (thrombosis) at McMaster University in Hamilton, Canada. She holds a Masters Degree in Health Research Methodology and is a Deputy Editor with the Health Information Research Unit, McMaster. She is Co-Editor of the ACP Journal Club and Co-lead on the CanVECTOR Knowledge Translation Platform.
Published: Friday, June 7, 2024
Please note that the information contained herein is not to be interpreted as an alternative to medical advice from a professional healthcare provider. If you have any questions about any medical matter, you should consult your professional healthcare providers, and should never delay seeking medical advice, disregard medical advice or discontinue medication based on information provided here.
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This Evidence Summary was printed from the CLOT+ website on 2025/03/30. To view other Evidence Summaries or to register to receive email notifications about new Evidence Summaries, please visit us at https://plus.mcmaster.ca/ClotPlus/Articles/EvidenceSummaries |
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, McMaster University