Number Needed to Treat: Treatments Don't Work Like You Think They Work

One of the problems with the way we discuss health interventions is that we see them in black and white. Something is either good for you or bad for you. Things are rarely that simple, though. Moreover, there's "good for you" and "GOOD FOR YOU". How do you tell the difference? Watch and learn.
Almost all of the data for this came from the amazing website TheNNT (thennt.com). You can go there to see those and more.
Additionally, Aaron's new book is out! Please consider buying a copy. He'd really appreciate it! dontputthatinth...
John Green -- Executive Producer
Stan Muller -- Director, Producer
Aaron Carroll -- Writer
Mark Olsen -- Graphics
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[@BlakeMcTavishe]

Debunking long held beliefs is one of my favorite types of videos. Please keep doing these!

[@Srewtheshadow]

He has so much beautiful math and research too :'3 Oh and he's fair about it too, don't forget that! :3

[@johnnyd6953]

He's just going one step further but still being black-and-white. If a pill prevents cancer in 1/50 people, it doesn't necessarily do nothing in the others. Cancer is also not a perfectly discrete event, and there are markers of ill health that precede it, just like prediabetes. If the pill prevents cancer in 1 guy, then it might prevent the transitional stage in, say, 20 guys. And that would be a large QOL improvement. Aspirin is a great example of this. It's use for preventing heart attacks is slim, but it has a massive plethora of other beneficial effects, and almost zero downside of taken under the care of a doctor

[@kennyc002]

NNT really is a great way to quickly determine whether something is clinically significant or not, even though things are statistically significant, still.

[@kennyc002]

Fortunately, number needed to harm has the same calculations as NNT. You can really quickly find both numbers given the absolute risk reduction of a therapy and the attributable risk (the harm) to see how much NNT vs NNH there is. The rest of that is a judgment call.

[@claybutler]

This should have a billions views. Absolutely essential to understand risk versus benefit.

[@troyadams19]

This was excellent, might be the most informative and simple video on the efficacy of drugs I've ever seen.

[@sunshinetomato]

This is really helpful to me. I have had doctors try to convince me to do things I'm unwilling to do or cautious about, and I haven't had the language to have a productive discussion about it. Now I will know what sorts of questions to ask.

[@AaronBrooks1]

Healthcare Triage I'd recommend being avoiding statements along the lines of "no benefit whatsoever." We really mean no quantifiable benefit. There may be interactions with other drug, diet, lifestyle changes that could magnify the benefit to meet the criterium. Also, while the patient may have still had the negative outcome (say, heart attack) it may be milder or they may have better recovery. Saying "no benefit whatsover" is a similar binary categorization that you are aiming to correct. Rhetorically, it's very easy to fall into these binary traps when trying to make a point. I really appreciate your videos, thanks!

[@TassieJake]

Facts are facts thou. You're just sugar coating because you feel it's bullshit

[@ptolemycleopatra]

I just found this channel this week and I'm loving it! So much great information in short bits that I can understand and actually apply to my life. A lot better than all these articles about a "study that was done that shows" that leaves me with more questions than I had in the first place. Thank you so much for the great work you are doing.

[@healthcaretriage]

Thanks!

[@edoist16]

Please, we should put up this KZbin channel on TVs at waiting rooms in hospitals and clinics in Canada and the US. Gives waiting patients something interesting to watch, and they could actually make informed decisions. Patients have better expectations, doctors waste less time explaining the same thing over again, literally everyone wins!! Plus, streaming the video costs nothing. Please Healthcare Triage , do your own small study with some local clinics, and see how it affects patient outcomes! :D

[@kennyc002]

I just want to say that I really appreciate your videos here. Despite my personal issues with medicine, I really think your focus on evidence-based medicine and the emphasis on research has made you one of the best resources on the internet with regards to medical knowledge. Keep up the good work!

[@tmetz687]

Your videos are amazing and it shocks me how little I really know about health and healthcare. Thanks for the info and keep up the good work. I really wish this stuff was taught to the general public.

[@anisbuzreg8246]

this is the best video that i have watched in years , this is the first i watch a video with out fast forwarding it!

[@Moholeoel]

Your videos are brilliant and fascinating. So informative! This NNT and the other NNH are both particularly helpful. Thanks.

[@CarbonHyperbole]

i work in the "natural" section of a grocery store. If i could get everyone one in the world to watch one video, it would be this one. we get tons of people chasing super expensive diets and supplements that almost certainly aren't worth their money.

[@GlobalJargen]

Im revising for medical finals and you've saved my life! THANKYOU! Please keep making stats easier to understand

[@Urspo]

Thanks as an MD I've never had a good concept on number to treat; this was quite helpful !

[@jlchambe77]

When people talk about number needed to treat, they usually talk about how the therapy has little benefit for the individual. (Such as the NNT of 61 for Mediterranean Diet). They often neglect to talk about the huge benefit when applied over a large population (such as if 1 million people ate it then there would be 16 thousand fewer heart attack, strokes, or deaths). That is a serious savings of money, lives and disability when applied to a state or country.

[@garrettkajmowicz]

Am an EMT in PA. The State added CPAP to the EMT Scope of Practice because (so I've been told) the NNT for CPAP to avoid an intubation is 6. That makes it one of the most effective treatments in EMS, possibly all of medicine.

[@dylanhardaway1259]

This show just keeps getting more educational!!! Keep it up guys!

[@freefalldamir5765]

Wish a lot more people would understand this. Especially when dealing with cancer.

[@friedmansfresh]

TY for this and the NNH video. After watching them I was able to ask the right questions to help me decide whether or not to start Tamoxifen recently. When doctors throw around relative numbers, especially the "your risk would be cut by X%" it can be very misleading!

[@ProfRoofs]

I’ve been trying to understand this for a long time and finally I do! Thank you!

[@ErovZ]

Omg, I would like to thank you so much, I have an exam about epidemiology and I finally understood this topic with your video !

[@toshihitsu1989]

the more i watch your shows the more i get to know about my moms field as a Nurse. and what goes on in the medical field.

[@kennyc002]

Ya, it's...a lot more going on under the hood than you'd expect.

[@saber1epee0]

Brilliant and mathematical reasoning. Thank you HCT for existing.

[@ghuegel]

Thanks for this. Statistics are hard for most people to understand intuitively and this video seems like it should help people understand.

[@BloggyG]

Love this series. Just posted this to my KHIT blog.

[@samquilter8300]

Just got looking at your videos, I feel it would be interesting if you got doctors thinking contrary to your research and knowledge and debated different topics, so people can see all sides of the story. This is really cool though, I really like the whole "No, that's not quite correct, here is why, but you should take care anyway" approach to things. It is a really nice way to display information and lay it out on a platter for people to take or leave.

[@nicholascampos1615]

Great video. We need this kind of material playing across colleges on the first day of classes

[@elliottmcollins]

Absolutely fantastic video and I can't wait for the next one. This is a simple and sound idea with applications all over the place, and getting it out of the ivory tower is a true public service. Also, I find myself wondering how this might apply to non-medical interventions like food stamps or microfinance. Some simplifying assumptions have to be made to talk about treatment as discrete, but having a NNT for "lifted out of poverty" or the like could be a nice on-the-box number to motivate discussion. To the research(/blogosphere)!

[@blacksage2375]

Man this just reconfirms my terrible no-drug bias. I ever get a doc trying to sell me a drug I need to remember to ask for the absolute reduction figure.

[@na-z-q4z]

Wow , the topic has been made so easy & simple .

[@AFrostyDonut]

This video really got me to think, but I probably wouldn't take a drug unless absolutely necessary; especially if it has a ton of side effects like most tend to have! Can't wait for next week's video :)

[@jmarcin]

This is one of the best damn channels on KZbin.

[@briankane8950]

Thank you ! You must be one of the bravest people in the world taking on billionaires like this. I'm getting a new doctor ! ( just because of the aspirin).

[@strikerj22]

It should be noted that in the aspirin example that he specifically said FIRST heart attack. The numbers for secondary prevention of heart attack and stroke are different.

[@rogerwilco2]

I just discovered this channel and it's quite good.

[@philheaton1619]

Would you do this calculation for some other recommendations? Stop smoking, never start smoking, limiting calorie intake, exercise, laproscopic surgery, weight loss, etc.

[@warriorhermione]

The problem with absolute risk reduction is that it depends on the original risk: for instance, a person's chances of getting a heart attack in the first place. Since people's risks for different conditions vary, relative risk reduction is much more helpful if you're trying to evaluate a drug, and absolute risk reduction would be helpful on a person-to-person basis. A drug with a 50% relative risk reduction for heart attacks would be helpful for someone with a 50% chance of a heart attack, but it would not be recommended for someone with a 1% chance.

[@jwdogg1551]

Hey Healthcare Triage! Could you guys do an episode on antidepressants and, if possible, antipsychotics? There's some conspiratorial controversy on these medications and I would enjoy a thorough video on this topic. Thanks!

[@YouWillNeverKnowMan]

This channel is awesome. Great discovery!

[@eugenetswong]

This is amazing. I feel like I have been kept in the dark all of my life.

[@lightningburn]

could you do a series on the benefits and weaknesses of different studies: RCTs, cross sectional, cohort studies?

[@bhunterwillis]

Can you do a video on the advertising of drugs and how it affects our drug usage?

[@skiz686]

Hey Healthcare Triage. Love this channel. Ever consider doing a episode on combating the claims of the anti-psychology movement? Not that the field of psychology is without room for criticism but I think your way of investigating such sensationalized views would be helpful.

[@Farfromhere001]

You pissed me off with the GMO episode but you redeemed yourself with this one! Good job!

[@ltc0060]

I'm surprised this video did not come back from dead after vaccine efficacy discussions. Man, it is awesome to find an explanation years before covid hit. Because this video and its conclusions is not biased due to covid-19 debates and so on. However, it might be biased due to other problems, but at the moment I don't care about those problems. Thanks.

[@jakev48]

Could you do an episode on fluoride in water? I think it would be interesting for folks on both sides of the issue.

[@MichaelYoung20]

I would love to see a table of behavior changes ordered by ascending numbers needed to treat, for various demographics. What are the best things I can do today to extend my life and improve my quality of life?

[@GarethField]

Probably depends on your genetics and demographics

[@haute39234]

it bothers me to no end, that we don't live in a society that doesn't actively make decisions on clear and established evidence based studies. There's almost always a study for everything (even outside of healthcare), and yet we all make decisions predominantly emotionally or intuitively, based on some soundbite and antiquated but widespread common knowledge (however flawed).

[@kennyc002]

Maybe in other fields, but in medicine there is a huge emphasis on evidence-based medicine. My 4 years of medical school hammered in evidence-based medicine as the holy grail of medicine. Core measures for many different chronic diseases make sure that every doctor is held to some measurable standard by which evidence backs the standard. Thing is, even such standards isn't always upheld due to existing circumstances, and it is in these circumstances that truly make a doctor shine. Anybody can know to follow standards, but it is those when the standard isn't quite the best fit for the patient where a doctor can make it better.

[@haute39234]

Medicine is definitely one of the better ones. I'm not in the field so I can't comment on an individual or personal front, but I meant more macro problems. Eg. in healthcare: preventative vs reparative care, money vs treatment, location vs. quality of treatment, fractured health networks and inefficiency, etc. Specifically I was thinking about creating policy in a social sense, about fields outside of science, like economics, justice, or politics. They seem to base their plans on segregate theories, and biased beliefs, rather than multifaceted cause and effect, which is primarily driven by human behaviour. but I could be a cynic.

[@stonescorpio]

Very interesting video! I really appreciate the ones that deal with odds and statistics. Two of my siblings are biostatisticians, and these help me understand their conversations. :D

[@YourArgument]

I would encourage you to consider the real, and well documented effect of placebo in an educational video such as this. Even though you cannot put hard numbers to that effect as easily as you can on these other statistics...

[@EnigmaHood]

Brilliant video as always. Amazing how much money is being needlessly wasted on what's essentially false advertising. I'd be interested to know what the absolute risk reduction is on cardiovascular disease for drinking red wine every day.

[@GregTom2]

You're judging too fast. A high NNT on itself doesn't mean anything. Ex: aspirin 80 mg has little benefits, but little cost, and the cost to treat 1667 people might very well be as low as 60 000$, which is less expensive than the treatment and surgery of one person with a heart attack. Overall it IS cost effective, and as such we can't call this measure "wasted money". Just because it doesn't work how you think it does... doesn't mean it doesn't work. Drugs are effective on populations, not on individuals. Trust me no insurers would cover them if they were just "fake advertising".

[@EnigmaHood]

GregTom2 It's wasted money for an individual, possibly cost effective for society, assuming your numbers are correct. "Just because it doesn't work how you think it does... doesn't mean it doesn't work." I never made any claims about what I think aspirin does, so that's a strawman. Assertions are not important to me, what matters is evidence, and if the absolute risk reduction for heart attack or stroke by using aspirin is low, then it's low. "Trust me no insurers would cover them if they were just "fake advertising"." I'm not aware of health insurance covering over the counter medicine like aspirin. But if they do without any out of pocket spending from the individual, by all means they should continue advocating for it. It's just a waste of money for an individual to buy aspirin for that purpose.

[@drsheikh]

Thanks for explaining NNT

[@knuckles91444]

I know the difference between good for you and GOOD for you!

[@gephc4]

Well then, good for YOU. :)

[@cosmiccandy8704]

Really great video and breakdown - thank you so much!

[@Peapolop]

Can you please make a video discussing the benefits (if any) of a vegetarian or vegan diet vs the standard omnivore diet? I have been a lacto-ovo vegetarian since october and I've felt pretty much the same. The only benefit I can see is that I go to the bathroom more often. How good is the vegetarian diet? Is it really necessary to abandon meat or is it just the presence of more fruits and vegetables what makes the difference?

[@daniellasherman2270]

This helped me so much, thank you!

[@The1996Shadow]

Do a video about phone radiation Health effects. And knuckle cracking.

[@Hi_Unon]

Scishow (Made under the same basic group of people) Did a episode on that, it does nothing to the body in a negative way.

[@pjf674]

Sci Show just did an episode on knuckle cracking. Spoiler alert: it's harmless.

[@Srewtheshadow]

Peter Fitzgerald Hold my beer. Gonna go crack my knuckles in my mother's face.

[@davidalearmonth]

It would be interesting to see the function involved when it comes to Vaccines and other diseases. I expect it is a bit more complicated calculation, since it is way more effective if everyone gets vaccinated. (while still being at least partially effective / fairly effective for most individuals)

[@Tarathiel123]

Wow, fascinating particularly from a public policy stand point!

[@chesthaarora4165]

thanks for clearing doubt

[@TannytheRatty]

I have a huge issue with the add that played before your video... It was for a homeopathic remedy. Homeopathic. On your channel. You should complain to KZbin. Loudly. Very loudly.

[@daddyleon]

I've been seeing a lot of people mentioning RRR/ARR/NNT within the context of covid vaccines, pair that with the fear that some have of sort of spike carcinogen or other side effects, and I'm starting to worry.

[@lampshade1304]

Can you do a video on Australia's healthcare system?

[@lksbat]

Can you do a video talking about the effects of a vegetarian/vegan diet?

[@IceMetalPunk]

Quick question: speaking as a doctor, what was your opinion of the staff hotdog eating contest?

[@PIF95]

I'm confused. Why do you use the "absolute risk reduction" to calculate the NNT? It seems like the "absolute risk reduction" is regarding the affect of an individual, while the NNT is regarding the affect on a group. It doesn't seem like those have anything to do with each other.

[@RayenTrail]

can you do a video (sorry if you already have... this is the first one I've watched) on clinical vs statistical significance? It dovetails from this video nicely

[@bedwards1951]

Multiplier effect of "good diet", blood pressure pills and statins over lifetime makes it worthwhile. Treat arteries in early stage of disease and will get better results as there will probably not be residual risk seen in treating late stage disease. Statins cost $40/ yr. Safe after 27 yrs experience. Good lecture.

[@claytonhanson6438]

Not that it would be quantifiable, but it would be interesting to be able to see how the placebo effect would work here. I mean if 1 out of 1667 truly benefited medically from aspirin, did any of the benefit psychosomaticly?

[@biohazard18966]

Great Video! Love it.

[@PogieJoe]

Very good episode. I fear I've been one of those people swayed by good vs. bad logic here quite a bit more than I would like. :p Time to change!

[@mitchumsport]

great video! thank you. are there any good criticisms of this sort of statistical analysis?

[@litapermatasari3651]

Thanks for your explanation! it helps a lot

[@FeeblePenguin]

And for further clarification, the number needed to treat is also just a rough estimate, and not the real number. This is because if four people are using a drug that has a 25% success rate, it is actually about a 70% chance that one of them will receive successful results. However, those odds decrease with size. If you had infinite people and a correlating infinitely small chance, there is a 63% chance (1-(e^-1) to be precise) that one person should see successful results. Of course, though, because there is a 40% chance that two people would see success, the average amount of people seeing success in a trial (with X people and a 1/X chance of success, and infinities subbed in) seems to be around 1.7 or 1.8. I haven't done all the math ;). Basically the numbers will be close to that with any sample size over a hundred. Conclusion: 1.7 people would likely win in a lottery with 100 people entering and 1% odds. So, the Number Needed To Treat; the number of people needed to use a drug for one person to have it work, would actually be calculating the number of people (if the odds of it working are only a few percent above zero or less) needed to use a drug for it to work on 1.7 people, a fairly major difference.

[@7849monkey]

Thanks for telling us about this stuff. This is very helpful (:

[@Nyskbdka]

ahhhhhhh-mazing. by far my favorite explanation.

[@peanut12345]

Play with Stats goes back early medicine, what about the deathly side effects that take 2-5 years on a person?

[@folumb]

For NNT, it isn't exactly that 1 person out of 'x' will benefit and the others won't at all. It's more like, 1 person out of 'x' will for sure benefit (as defined by those giving the treatment) and others will experience a range of effects from harm to benefit and in-between. Other things like safety profile of the drug will determine whether those other people experience no change, mild improvement or worse actual harm

[@TwistedKestrel]

I feel like this video could have been more effective if the example treatments were contrasted with ones that worked for a larger percentage of people (e.g. Asacol has a NNT of 4)

[@JeremyStreich]

Has there been a Healthcare Triage on fluoride and the myths and facts about it? I vaguely remember mention of fluoride, but I can't find it. If it hasn't been, can it be a topic for a video in the future?

[@TemperanceRaziel]

Great stuff as always

[@DaniWithADifference]

You should get your units straight. The absolute risk reduction is: Old risk - New risk = Absolute risk reduction. If you really want to express it in percentages, do so on _both_ ends of the equals sign. The dividing by 100 is really dividing by 1 (100%) in disguise, so don't do that. The results would be the same, but it would be so much more understandable. E.g. 50% - 25% = 25% absolute risk reduction (or 0.50 - 0.25 = 0.25).

[@wilsonrestrepo1532]

Great explanation.

[@lalaithan]

If this was common knowledge, I think people could feel more in charge of their medical decisions and plans. But as time has shown, it's easier to rely on what marketing waters down and tells us because it's on our TVs, internet ads, and radios, not somewhere on the internet that you have to search for, a doctor's desk drawer, or deep down in PI sheets.

[@kibromfesseha9960]

So is there a special name for the ratio of number needed to harm over number needed to treat(NNH/NNT[or nnt/nnh])?

[@nonchalantd]

great lesson

[@cellogirl0096]

This is wonderful, thank you!

[@CandiPinki]

at 1:50 you forgot parenthesis on the last two equations...

[@TriCorce]

+Healthcare Triage Hey, mind if I caption this video? (Or to be more precise, if I captioned it, would you apply the captions?) I've got an assignment in my ASL class and an interest in telling people how to use math to improve their lives. You've got a Deaf audience who probably struggle through some of the awkward KZbin machine captions. I'd fix that. Win/win/win!

[@dear_reader]

There's a bit of bad math in this, the chance that you will have one or more successful trials out of 4 trials when the chance of success is 25% (see around 4:30) is calculated with cumulative binomial probability, not with a simple division of 100 and the probability of success. In reality, across 4 trials the probability you will have 1 or more successes is (4 choose 1) * ((1 - 0.25)^3 * (0.25^1) or roughly 68% -- Edited for clarification and grammar.

[@lify1910]

numbers may seem small, but when you blow them up to a population level.... we are talking about a lot of lives

[@bi1iruben]

Whilst I agree NNT is useful for indicating the degree of benefit, the NNT presumes all the benefit is seen in one patient. So if we treat 4 people, and only 3 get a disease within the year vs 4 if untreated, there is a NNT of 4. But in reality some people get no benefit from a drug, some get a lot, but there is a continuum here - some people may get partial benefit. So if instead consider NNT of 4 with the benefit spread out, then instead of 100% prevention to 1 patient, one has 25% beneft amongst 4 patients. So if all 4 of our patients still get heart disease eventually, but at a 25% longer time interval than previously, then the NNT is still 4 (if one counts patients from a larger sample size), but that does not mean 3 out of the 4 gain no benefit at all (or that only one has just a 25% chance of benefit). Now of course however one divides/spreads out benefits of a low-number NNT, a NNT of 1000 is going to benefit few, or at least only very slightly to most people.

[@Freduccine978]

if my doctor prescribes me a treatment, can i ask her for the NNT and NNH? And would she know? Should I expect her to know?

[@einsibongo]

Thank you for the video.

[@itisdevonly]

This is a good and important topic and was well presented. Most people don't understand this or why relative risk reductions can be misleading. I feel like you put the Mediterranean diet out of context though. First off, you didn't specify what it was treating, or how other treatments compared. In terms of treatment for heart disease risk, the Mediterranean diet has the lowest NNT of any treatment studied to date. It may be inconvenient to implement, but it comes at a relatively low cost and without all the nasty side effects that come with taking drugs. And chances are, the reason it's successful is that it's doing a better job of actually treating the cause of the illness rather than the symptoms. Is it the best diet out there? Maybe not, but it's definitely proved better than the control diet of "eat whatever the fuck you normally eat that made you unhealthy in the first place."

[@watsonzulu9008]

This is excellent

[@beccybecster]

Well at least in the aspirin example, wouldn't someone who was treated with aspirin have a higher risk for heart attack or stroke than the average person? Do those 1667 people have the higher risk to begin with or not?

[@kamk.1704]

Great video.

[@bhunterwillis]

Also, with these drugs, are you downplaying the placebo effect and how it plays into the success of treatment, even though it may not be directly tied to the drug?