Can flossing reduce your risk of a stroke?

Hi , I'm Dr Bobby Du Bois and welcome to Live Long and Well , a podcast where we will talk about what you can do to live as long as possible and with as much energy and figure that you wish . Together , we will explore what practical and evidence-supported steps you can take .

Come join me on this very important journey and I hope that you feel empowered along the way . I'm a physician , ironman , triathlete and have published several hundred scientific studies . I'm honored to be your guide . Welcome , my wonderful listeners to episode 35 . Can flossing reduce your risk of stroke ?

Well , it's a fascinating question and we , of course , don't want to get a stroke . And there was a recent study and lots of headlines in all the news media that said flossing reduces our risk of stroke by 20 to 50 percent , depending upon the type of stroke .

Now , this was based on a presentation at the American Stroke Association's International Conference on Stroke and it was widely picked up by the media , by the New York Post , the San Francisco Chronicle , youtube post , the San Francisco Chronicle , youtube Times , uk Jerusalem post , and we are going to dive into this study shortly . But why discuss this topic ?

Well , the headline is really catching Flossing reduces our risk of a stroke . Now the question , of course , is is there anything to this and beyond just this study ? Are there lessons to glean from all the headlines ? All the attention ? Are those lessons things that can teach us how to approach future headlines and whether to believe it or not ?

Now , as you may recall , in episode 22 , health headlines helpful , harmful or just plain confusing we explored a headline that was worrisome , that intermittent fasting caused heart attacks , and now we did a bit of myth busting there and we showed a lot of the problems with that study .

Is it the same scenario here , where this hype exceeds what the evidence tells us ? Well , stay tuned , and we're going to figure this out . As I was thinking about explaining

to you , my listeners , why are we doing an episode like this , I realized I was destined . It was my destiny to do this episode Now . I didn't know it 30 years ago , when I was visiting my dentist and at the time she had just come back from a conference in Hawaii .

So this is in the 1990s or so and at that conference , basically , she learned how oral health , mouth issues , could cause heart disease . And I'm an internist , I'm a physician , she's a dentist and she's telling me about heart disease and she was saying , oh , we must brush our teeth and floss our teeth and that will potentially help the risk of heart disease .

And she was very excited about this and told all of her patients my wife and my kids and everybody else . It turns out she may have been ahead of the medical community Back 30 years ago . This was not something that was commonly discussed . Well , we'll come back to this as well . Before we dive into the content , I have a request .

This is episode 35 , so I've been doing a whole bunch of these and I would love to get feedback from you about how I'm doing the topics you like , the topics you want more of , and there's a brief , brief questionnaire . It'll take you like two minutes and the link is in the show notes .

So please , if you can do , take a couple of minutes and give me that feedback . Some of the questions I really want to learn from you do you like episodes that summarize evidence on a topic Like is there evidence that sleep is important or that nutrition matters . Do you like myth-busting ?

In some cases maybe today's episode is myth-busting Certainly the one on seed oils fits into that Do you like that type ? How about the ones where I share a personal health journey , like the one I did recently on my needing a brain MRI and what happened ? Also , the framework episodes Do you Like your Doctor ?

Where I sort of lay out how to think through things . So I'd love to get your input on that , on any new topics you might suggest and , most importantly , how long my episode should be . I've aimed for 30 minutes . Should they be 20 minutes ? Should they go 40 minutes ? Are you okay if they go longer ?

I have tried to avoid many of the other health podcasts length of an hour hour and a half two hours , all right . Well , let's dive into our study for today and our topic today Can flossing reduce our risk of a stroke ? Now some stroke facts , because stroke is not something we talk about all the time .

Heart attacks we talk , not something we talk about all the time . Heart attacks we talk about , we hear about all the time . Stroke for a while hasn't been really front and center Yet . There's about 800,000 strokes that happen in the US every year , and about every 40 seconds there's a stroke , and about every three minutes somebody dies of a stroke .

Equally importantly , stroke causes major disability . You might not be able to move on one side or a part of your body , you might not be able to speak . Well , all sorts of disabilities can come out of it . So it's a really , really important topic and could something as simple , really as simple , as flossing help us ?

Well , we need to talk a little bit about your mouth , oral health and how this possible solution or reduction in risk could occur .

Well , we have , at any one point in time , about a billion bacteria in our mouths , just on our gums , on our teeth , in the saliva , and it is known quite clearly that if you brush or you're chewing , bacteria can and do get into our bloodstream . That , of course , doesn't sound very good .

Well , if bacteria get in our bloodstream , they could cause direct damage , meaning those bacteria could go to other parts of our body and that could create problems for us .

Or and I think this is perhaps more likely that the bacteria in our mouth that get in our bloodstream cause what I would call indirect damage , and that indirect damage is that it creates an inflammation , an inflammatory reaction and inflammation has been associated with heart attacks , cancer , metabolic disorders and the like .

So this issue of the damage from the bacteria is really a sensual question . What we also know is that if your gums that surround and hold in your teeth , if they are inflamed , if they are infected , more bacteria are around and more bacteria can get into our body and cause problems .

We also know good studies on this that if you brush and floss , it can reduce it does reduce your risk of gum disease . So theoretically now we're building an argument that the bacteria in our mouth could get in our bloodstream , could cause inflammation , and brushing and flossing has been shown to reduce that risk of inflammation in blood bacteria .

Now we haven't made the leap yet to stroke or heart disease , but at least we're beginning to build a story and we have a lot of room for improvement in oral health . Studies show that Americans do brush pretty regularly , but they don't floss very regularly . Here's some

data . So in a study that was published , 90% of us do brush at least once a day and 60% of us brush more than once a day . I'm a twice a day brusher myself , religiously , in the morning and at night . Now flossing we're not so good as Americans about flossing . A third of us don't floss at all .

A third of us floss basically about once a week and only a third of us floss on a daily basis . Well , I'm a nightly flosser and I find that it makes a huge difference that even though I've brushed and gargled with mouthwash , there's still a lot of junk on my teeth .

I've also found this is a simple hack that if you floss in front of a mirror close up , like makeup mirror boy , you make a lot better job of it than if you just floss in general , not looking at a mirror or even looking at your bathroom mirror .

So if flossing were to matter and really if the study were true , gosh , there's a tremendous opportunity here , because a lot of us don't floss or don't floss really well . Okay , let's examine some more of the evidence connecting oral health with heart disease .

Is it that a poor mouth , with gingivitis and other things , that it causes a heart disease or stroke , or is it just common factors ? So perhaps the mouth doesn't cause stroke and heart disease . Perhaps it's things that hurt the mouth also hurt other parts of your body . So here's a perfect example Smoking .

Smoking , we know , raises your risk of a heart disease or stroke . Smoking also worsens your oral health , so it may not be that the mouth is causing the problem . It just may be there's a common underlying factor like smoking or diabetes or getting older .

Or , as the article might suggest to us , it is the presence of the problem in our mouth , your bacteria and gum disease , that causes heart disease or stroke . Now , as we've talked about many times , correlation doesn't mean causation .

Just because we see that people with strokes have mouth disease or people with heart attacks have mouth disease doesn't mean one causes the other . Well , the American Heart Association reviewed the evidence and this is how they saw it . They said well , there's a lot of observational studies that support the relationship between mouth

health and heart health , but they summarize that those observational studies don't say it's causative . It just means that they are potentially connected . Unfortunately , there haven't been any randomized controlled trials where some people get good oral care , some people don't . We follow them for 20 , 30 years and we see who gets heart disease or strokes .

Unfortunately , that study has never been done . I don't know if it ever will be done . Well , if the mouth and the heart , mouth and the stroke are causative , that the problems in one area create problems in the other . The theory is that it's due to , as I mentioned earlier , inflammation .

Now we do have pretty good data that inflammation is associated with heart disease .

One of the blood things that your doctor may order for you is called a CRP or C-reactive protein , or high-sensitivity CRP , and it's been shown many times that if that blood level which reflects inflammation is elevated , there's a much higher likelihood of having heart disease later on .

And there's reasonable data that said , if you improve your oral health , it lowers those inflammatory markers . So we're starting to build a case that oral health relates to inflammation , the case that oral health relates to inflammation . We believe inflammation relates to heart disease and the like . But again , this is all just building a theoretical argument .

All right , before we get to flossing , there is some data on toothbrush , brushing your teeth and heart disease . And if you brush just once a day or less than once a day , you have twice the risk of heart disease than if you brush two or more times a day . Again , all this evidence is observational .

We don't have the randomized controlled trial , so we can't officially say there's a cause and effect relationship , but it is intriguing and maybe someday there will be that randomized trial .

Okay , now we are ready to go on to the flossing study and to see whether the headlines are true or likely true and if not , what does it teach us about reading headlines carefully and understanding whether to believe it or not ? Well , the title of the study was regular dental flossing may lower risk of stroke from blood clots and irregular heartbeats .

This was a study , as I mentioned , that had been presented at a conference and it was from what was called the ERIC study atherosclerosis

risk in communities .

This is a large study that's been tracking over 6,000 people over 25 years , and the purpose of this big study was to see things that might relate to heart disease , so things like they might have measured 25 years at the beginning of the study , whether you smoke , whether you exercise , all sorts of different things and some of the things they asked related to

oral health , and what they found was about two-thirds of people in this long-term study again , not a randomized trial , just an observational study about two-thirds of those folks did , in fact , floss , and those who flossed when they followed them over time had a 20% to 50% lower risk of a stroke Incredible . Now , it varied by type of stroke .

That flossing didn't reduce your risk of all types of strokes , but important , important ones . Interestingly , they didn't find benefit for brushing and they didn't find benefit for visiting your dentist . So this is the first inkling that maybe this study isn't as valid as the headlines would suggest .

But if it's true and there is that large reduction in stroke simply by flossing , maybe there could be as many as 50 to 150,000 fewer strokes in the United States each year . That is extraordinary . And why is this not what the firemen call a five-alarm fire ?

Now , when there are fires , there's alerts that go out and a five-alarm fire means the fire is out of control . Bring every resource you have , let's fight this fire . So why isn't this study and flossing a five alarm fire where everybody should be talking about it ? Well , I have concerns with this study , not surprisingly . That's why I'm doing this episode .

Surprisingly , that's why I'm doing this episode . Like our episode on health headlines and intermittent fasting causing death from heart disease , this set of headlines and study has some of the same problems . This was not a peer-reviewed published article . It was merely an abstract that was presented at a conference .

So somebody wrote up a paragraph or two about the study and presented it at a meeting , and maybe there were a few different questions , but nobody has seen the full data , how the study was done , sent it out to other experts and ultimately undergo peer review and then publication in a peer-reviewed journal . None of this happened .

I also mentioned that flossing seemed to help , but brushing and going to the dentist two other things that we would think would go along with that benefit that didn't turn out to be true . So this raises a question .

When you do a large study like this and you measure a zillion things at the beginning and then you look at lots of different outcomes later on , you have a wonderful database . But that database people can play with and they can say well , I wonder if eating apricots causes heart disease or stroke .

Now , I don't know if they actually ask the question about eating apricots , but if you play with the data and ask it many , many , many questions , statistically you're going to come up with something often that is abnormal , when in reality it isn't . From this long study there's been 2,300 published articles .

Well , the way that happens is people are working with that database regularly , testing all sorts of hypotheses , and this was just one hypothesis that was tested and found to be interesting and positive . That doesn't mean it's true . So how do you sort out whether an observational study finding like this is true or not ?

Well , first of all , I don't get excited if it's presented at a meeting and it hasn't been peer-reviewed , published . But about 60 years ago there was an epidemiologist , somebody who studies the rates of disease and the causes of disease in England . This is where this epidemiologist was based . Who studies the rates of disease and the causes of disease in England ?

This is where this epidemiologist was based and his name was Sir Bradford Hill and he developed nine different criteria for causation . So when you look at an observational study and you find , oh look , apricots seem to be related to heart disease , you can ask yourself these sets of questions and that will make it more or less likely to be true .

I'm not going to go through all nine . Maybe over the course of upcoming episodes I will , but I want to highlight a few . The first is when you see something like this , you have to ask yourself is it plausible ? Now , if it was my hypothetical example of apricots causing heart disease , then I got to come up with a theory why might apricots do this ?

Well , in this scenario , is there a plausible relationship between oral health and a stroke or heart disease . And , as I walked through before , there is a plausible connection that poor oral health relates to bacteria . That bacteria could get in your body that could lead to inflammation . Inflammation leads to these types of problems .

Okay , so there is a plausible relationship , so they get a point for that in my estimation . Well , the next criteria is how strong was that finding ? You know , was it a 1% increase in risk or , in this case , a 20% or 50% increase ? So that also ups our likelihood of causation .

Now we get to the ones that they didn't do or what we don't know about this . The first is consistency . Bradford Hill criteria is well . Has it been reproduced by other investigators in other databases , in other areas of the country or the world ? Well , the answer is no . There haven't been another study looking at flossing , and so it fails on this criteria .

We've talked in the past about something like dose response . That means if you think something causes a problem like smoking and heart disease , is there a dose response relationship , meaning if you smoke one cigarette a day versus 10 , versus 20 , versus 40 , if you think smoking is a problem , does it get more risky if you smoke more ?

So is there a dose-response relationship to flossing . Well , flossing once a week is better than nothing . Flossing once a day is even better . Flossing multiple times a day could even be better still . Well , that would be really important data , but we don't know , the study didn't talk about it , probably it wasn't measured , but that would help us .

And again , as I've mentioned , I put all of this in a category of well , it's not published , it's not peer-reviewed . Will there ever be an RCT , a randomized controlled trial , to test this ? I don't know . So we may be left with the Bradford Hill criteria and observational studies .

Well , let's wrap up . Without a doubt , brushing and flossing are important for our mouth and oral health . Does oral health cause heart disease and stroke ? It's really plausible . There's a lot of observational studies , but it's still an unanswered question . Third , it is uncertain whether flossing reduces our risk .

Well , if you want to know what I do , I brush twice a day and I do this absolutely every day , and I floss religiously . I floss at the end of the day , when my mouth is full of junk and I can do a good job is I can sit and relax and do that .

I've also found no science here that the water jet , the thing that sprays water at your teeth is really , really helpful . I can do all the mouth care I want and I still get junk coming out when I use the water jet , so I do that as well .

Actually , I begin by gargling , then I do the water jet , then I brush my teeth and then I finish it off by flossing . This is just my once a day routine . In the morning I just brush Well , as always . I hope that you live long and well , that you live long and well and perhaps consider adding more flossing and brushing to your daily routine .

It may or may not impact your likelihood of a stroke , but it will definitely improve your oral health and by itself that's a really good thing too . Until next time , take care .

Thanks so much for listening to Live Long and Well with Dr Bobby . Until next time , take care . Want to receive my newsletter on practical and scientific ways to improve your health and longevity ? Please visit me at drbobbilivelongandwellcom . That's Dr . As in D-R Bobby . Live long and wellcom .