What do anticoagulants reduce our stroke risk to?

Me again :)

I keep reading online that afib increases rid of stroke 5-6 fold (depending on the source).  Whatever the stats it's clearly a huge risk.

What is not clear is whether they mean that's the risk WITHOUT anticoagulant or even with it.  

If you are on the drug, by roughly how much does it reduce the stroke risk back down to?

Sorry for all the questions but I am finding information gaps in my reading and I really need to get a firmer picture.  Thanks all. 

21 Replies

  • Do look at AF Association website as the info there is approved by NHS.

    Regarding your question. the basic fact of having AF increases your stroke risk by five times. Anticoagulation reduces that to a level which although not that of non AF people is much lower. I'm sorry I can't give you an exact figure but maybe 20% as opposed to 500%.

    You then have to factor in other health issues which is where CHADS and CHADSVASC come in. This  adds factors such as prior stroke or TIA,  age,  diabetes, high blood pressure and any other heart disease and produces a score based on which you may be advised to take anticoagulants. Many people believe that just having AF should warrant being on anticoags but current guidelines do not  say this.  We acknowledge that the current system does not take into consideration other life style factors and is far from perfect but currently it is the best we have.

    When considering anticoagulation one must also consider bleed risk and there is a scoring system known as HASBLED which adds other factors and may indicate that the risks of bleeds is higher than that of clots in which case one would not anticoagulate.  This only usually applies with the elderly or those with other health issues

    I would stress that stroke risk is not dependent on the number, frequency or strength of any AF events and once given is for life regardless of  any outcomes from either drugs or  intervention.

    I hope that helps


  • Please remember that all stats and risk factors are made up from what is called 'herd statistics', a certain percentage of people will suffer a stroke in the general population - risk factors may increase the numbers of stroke within a certain group of the general population - such as AFers but whether or not you will be one of them or not is a known unknown.

    In other words no one really knows whether you or I, as an individual, may be protected from stroke by taking anticoagulants or can give you accurate percentages of how they may reduce your risk.  I think  it is a really difficult dilemma - are you better taking them or not taking them?  For some like Bob being on anticoagulants for life is a no brainier, for me it is a much more difficult decision.  And we both are now AF free but evidently the risks endure even if you currently do not suffer episodes,

  • I've never heard of anyone on this forum or elsewhere, who has had a TIA or stroke while on anti-coagulants so I guess it's pretty rare.    You've also less chance than most others on the plane of having a DVT too - now there's a bonus!     Don't forget that among warfarin users there's a good number who think they are protected but, as a result of poor INR management, are not.      Being on apixaban certainly helps me sleep at night.   

  • I have a good friend who has had two strokes while on long-term warfarin. It happens though obviously your risks are reduced. 

  • Good question Ahab, I have not seen anything to advice me what my current risk is in simple 1 in 1000 type terms nor what it will be reduced to with anticoags in the same simple terms. As CDreamer says there is good reason for this.

    It then becomes a personal decision with any partner. I don't take them but I use this fact as a driver to eat the right food, take the right supplements, drink more water and exercise more regularly. 

    Good luck with your choice.

  • The statistic that is generally used is that anti coagulation reduces your stroke risk by about 70%. 

    However I fully agree with the qualifications given above. 

  • For the benefits of warfarin, see: Singer, DE, et al. The net clinical benefit of warfarin anticoagulation in atrial fibrillation. Annals of Internal Medicine, Vol. 151, September 1, 2009, pp. 297-305.

    The benefits depend entirely on risk profile. For those with a CHAD2VAS2 score of 0, the statistical change in stroke risk is roughly zero. For those with a CHAD2VAS2 score of between 4-6, the reduction in risk is 2.2% per year (i.e., roughly 2 people in every 100 each year will benefit from taking warfarin). Such a benefit might sound trivial but becomes hugely significant over 10 years. 

    For estimates of risks as a function of CHAD2VAS2 score, see the following article: 

    Stroke risk in atrial fibrillation: Do we anticoagulate CHADS2 or CHA2DS2-VASc 1, or higher? by Jonas Bjerring Olesen; Christian Torp-Pedersen, Current Controversies, 2015. 

    This article reviews recent studies of stroke risk and they consistently indicate that if you have a CHAD2VAS2 score of 0, stroke risk is roughly the same as for people without atrial fibrillation ("five times the risk" misrepresents existing research, but has been helpful as an attention-grabbing way to raise awareness about the stroke-AF link). No researcher has claimed such a high stroke risk among people with this CHAD2VAS2 score. 

    Having said that, it is important to know that stroke risk for people with AF is dynamic, so even if anticoagulation is not recommended at this time, you should monitor your risk profile regularly, and ensure you initiate anticoagulation treatment as soon as it becomes advisable. 

  • Bob,

    You said:

    "I would stress that stroke risk is not dependent on the number, frequency or strength of any AF events and once given is for life regardless of any outcomes from either drugs or intervention."

    Why is this? and what study or trial was the basis for this?


  • Yes I don't really understand that either....surely you are at risk every time you have an AF attack as then there 's a chance for blood to pool...but if it's not pooling any other time when you have normal beats then I'm not seeing how your risk can remain constant.   Also it would be bound to change over time dependent on lifestyle changes ageing other illness etc etc.   I will ask my cardiologist and report back :)

  • I used to think that not having AF reduced your stroke risk but if you listen to any talk given by experts (Richard Schilling for one) you will find that their opinion is that the effect of having AF changes the internal structure of the atrium in such a way that pooling may be encouraged. Think of a stream and put some weeds on a section of the bank or some rocks on the stream bed and see the effect it has on the water flow.

    Regarding risk factors the CHADSetc system is such that once given a score can  not be removed so for example if you have high blood pressure you score one. Even if you change your life style or  take medication to reduce it,  that score stands. Since age is one factor, people are often told "oh you don't need to take anticoagulants till you are 65 " as if a birthday suddenly increases you risk but as you say Ahab it is a fluid process.


  • The risk doesn't suddenly appear on your birthday, it gradually increases until one day it suddenly becomes greater than the risk from taking Warfarin.

  • i have also come across a similar quote as above, and had to re-read several times!  Would be nice to have someone from the medical profession, elaborate on what this means.

  • Hi Dave

    Not a medical expert, but when I have heard this question answered at conferences, it's because you do not need to have an "AF Attack" to necessarily to be at risk of stroke, firstly you may have mild or more serioud cariomyopathy (enlargement) especially in the left atria, secondly you could quite easily be in AF and not know it (I am all the time and seldom know that I am in AF) The rate of re-occurence of AF is high even for those who are AF fre after ablation.

    What they generally say is what was your CHADS score when you had AF. It it was high then you need to probably be anti-coagulated for life, if low then it may be possible to come off.

    There are quite a lot of studies if you google it, such as


    But as in every case, not everyone agrees.

    Be well


  • "many short episodes of AHRE could result in the same AF burden as a single long-standing episode"

    "it appears unlikely that rhythm control therapy alone can be sufficient to prevent AF-related strokes"

    "rhythm control does not appear to suffice to prevent strokes in AF in the absence of oral anticoagulation"


    "decisions regarding the use of systemic anticoagulation more than two months following ablation should be based on the patient’s risk factors for stroke and not on the presence or type of AF"

    "discontinuation of systemic anticoagulation therapy post ablation is not recommended in patients who are at high risk of stroke as estimated by currently recommended schemes (CHADS2 or CHA2DS2VASc)"


  • The NICE guidelines for anticoagulation are here:


    You can see from the diagrams how many strokes occur under all the different scenarios. Don't forget to check you HASBLED score as well as the CHADS.

  • I have yet to see a study or trial that backs up these statements.

  • So which statements are contradicting their reference, then?

  • I think this thread is illustrative of the confusion and lack of clear information amongst AF sufferers and for some doctors about who should always take Acs and who may stop without incurring significant risk.

    I just spoke to my GP about going back on them by the way, given that I am starting to have arrhythmias again which are probably triggered by the drugs I take for the Mg which are known to trigger arrhythmias. 

    The vicious circle begins as I can't take Beta Blockers Ace Inhibitors or any anti-arrhythmia drug now because they are contra-indicated for Mg.  So overall, after all of my internal dithering and debating I am making an appointment to see the EP next month.

    Best wishes CD

  • CHADS2 Score and Corresponding Annual Stroke Risk

    CHADS2 ScoreAnnual Stroke Risk, %








  • My cut and paste did not turn out very well.  Here is the information again.

    Chads2 Score and Corresponding Annual Stroke Risk

    0  1.9%

    1  2.8%

    2  4.0%

    3  5.9%

    4  8.5%

    5  12.5%

    6  18.2%


  • How is that answering Ahab's question?

    BTW, the European Society of Cardiology recommends the CHA2DS2-VASc score over the CHADS2 score because it more accurately separates very low risk patients from low risk patients. The risk of a patient with a CHADS2 score of zero can vary anywhere from 0.84% to 3.2% depending on their CHA2DS2-VASc score.

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