Effectiveness of Warfarin

Something I don't seem to have seen anywhere - not spelled out anyway - is how warfarin (in therapeutic range) affects one's risk of stroke. For example I'm 1 and 2 on those two CHAD scores (sorry, I can never remember the full acronyms) which scarily tells me I'm 9 times more likely to suffer a stroke than the average member of the population. A 2.2% annual risk.

So what does warfarin do to that risk? Anyone know? It must reduce it otherwise we wouldn't be taking it, but by how much? Obviously we are talking statistics so we can't expect any guarantees but it would be nice to think that while I'm returning an INR around 2.5, that 9x stat is substantially reduced.....?

10 Replies

  • Hi Leelec

    I'm no expert, there seems to be a number of statistics bandied around, I haven't seen the nine times, but several articles refer to five times more likely to seven times more likely.

    There is an article here which refers to warfarin reducing this from 4.5% to 1.4%, but not quite sure how the maths works on that


    Several other articles then refer to warfarin reducing the risk of stroke by between 70% and 50%, and the major dfference seems to be age, as you get older the risk of stroke is higher.

    All I know is that at 59 having a stroke terrifies me, not so much the dying from one, but the thought of being do dehabilitated that I would need to be looked after is the really scary thought.

    My CHA2DS2-VASc is 0, but I was given the choice to continue on warfarin, and I seized it with both hands, better a few tablets than any thought of a stroke.

    Take care


  • Thanks Ian, I entirely agree - the thought of a stroke is sometimes almost more scary than a terminal illness. On the other forum Bob D suggests that, in the best cases, warfarin induced INR in therapeutic range should mean there is no greater risk of stroke than the average person in the population which is very encouraging. I've been in paroxysmal AF since age 60 in 2009 but I think I may now be in transition to permanent as the episodes recently have been lasting longer - currently in a 4-day one. I always 'feel' much more vulnerable to stroke during an AF episode but again it seems that the risk of stroke, whether paroxysmal or permanent, is much the same.

  • I think I also mentioned recently that AF itself is a risk inducer which once had can not be switched off. Any risk factor remains once given so high blood pressure treated with drugs to normal is still scored. As you say, the risk is constant even when you are not in AF but perhaps more likely if you are


  • Hi Leelec,

    The CHADS score and stroke risk figure is the risk IF you are not on warfarin. My risk figure is 20 since I've already had a TIA (often referred to as mini stroke), and also had high blood pressure in years gone bye. The TIA was scary enough and like Ian, the thought of a full stroke is even more scary. That is one reason that I am perfectly happy taking warfarin and usually try to keep my INR around 2.8. I've been in permanent AF for some years now so that's another good reason to keep "taking the tablets", as they say.

    Hope that helps.


  • Thanks Walter. Was the TIA while on warfarin or before you had started taking it?

  • Hi Leelec, it was before I started on the warfarin, although I had been diagnosed with paroxysmal AF prior to that. The TIA, that was diagnosed was in Nov 2000. I believe I had several more prior to that, that I never went to see my GP about. I now realise I should have, but was much younger and didn't know too much about it then. I am now 70 and have done a lot of studying regarding AF and TIA's since 2000. Also notice Bernard's post after mine. The 2 types of stroke are Cerebral Thrombosis, caused by a blood clot, the main risk with AF, and Cerebral Heamorage caused by a ruptured blood vessel in the brain. If the INR is not high enough then the risk of thrombosis increases and if its too high then the risk of a bleed increases. Hence the importance of keeping your INR within your therapeutic range, normally 2 to 3 for AF. I've twice had mine at 11 and involved a stay in hospital on Vitamin K injections to get it back down. After the second "high episode", when I was working away from home, I decided to get my Coaguchek Monitor so I could keep a weekly check on my INR. Sorry to go on a bit but hope it all helps.


  • Thank you Walter, that's all very helpful. Good to see you haven't had a further TIA since.

  • Hi leelec. I know this is not very helpful but as far as I am aware there are two types of stroke - those caused by a clot and those caused by a bleed so you pays your money and takes your chioce. I have A/F and am on warfarin but I personally believe that there is less of a chance for me to have a bleed stroke whilst on warfarin than a clot stroke if I am not. Makes you wonder if it is worth asking sometimes.

  • Thanks Bernard. Yes, aware of the two types. I guess the trick is to keep the INR where it should be.

  • My CHAD score is 1 (Blood Pressure) but have age on my side (59) I'm now in permanent AF, but asymptomatic. I was diagnosed with paroxysmal AF back in 2009. I was prescribed Warfarin back then, and remained on it for about eight months, but could never be stablised with INR only reaching the recommended level on all but a few occasions. I then moved onto Aspirin, which I took for a number of years. However, as we know, the value of Aspirin is now not particularly good as a blood thinner, so I always felt that I was at risk from a stroke. I discussed this with my GP, and in the first instance, was only offered to be moved from Aspirin to Warfarin. However, I would have liked to be moved onto one of the new novel Blood-thinners, and although turned down the first time, again mentioned my instability with Warfarin, and then was prescribed Dibigatran, which I started last week.

    However, like all of us on here, we want to reduce the risk of a stroke the best we can. I will have to see if I can find out the risk percentages that you mention above.

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