A brief conceptual introduction to hazard ratios and survival curves (also known as Kaplan Meier plots). Hopefully this gives you the information you need to interpret these numbers.
Thank you! Just one question. You say that Hazard ratio is the probability for an event to take place in a given time interval. In the table of Vitamin D levels and death that you use in the beginning of the video I can't see that the specific time interval for the hazard ratio is noted/specified, shouldn't a time intervall för the hazard ratio be specified then? (Maybe the time intervall was made clear in the text of the study?)
Well, so what does the hazard ratio that is written out in the beginning mean? What interval are we talking about? Isn't the point of Hazard ratio compared to RR to define a certain interval so we can see who is more likely to die in that interval? Otherwise why can't we just use RR? Shouldn't there be several hazard ratios presented, one for each interval??
6:27 You call the percentages ( 19% and 6%) 'hazard rates'. I'd guess the ratio then would be 16/9 (comparing the hazard rate). But this is not mentioned. Is the hazard ration the same as the hazard rate, or is it the ration of both? I also don't understand why they should be the same (I guess that's under the H0, no difference hypothesis). Still, nice video, very clear and (important) enjoyable.
Could you please explain why your hazard ratios aren't exactly in the middle of the confidence intervals? Does it have to do with lognormal distributions?
I got the idea that hazard ratio time element is important. but I didn't get the idea of "the hazard ratio is 2.5 it means that in a particular given interval, one group has a 2.5% 2.5 times more likely chance of experiencing the event (in this case death) then the other group does." how can i know this particular time from the table??
How to compute the hazard probability using survival estimate ? I have embedded this formula to calculate using cumulative baseline hazard but I am getting higher integer values for hazard rate(hazard probability) : 𝑆0(𝑡)=exp(−𝐻0(𝑡)) - extract cumulative baseline hazard ; ℎ(𝑡|𝑋)=ℎ0(𝑡)*𝑒𝛽𝑋 - and then hazard rate using baseline; however, I see very high hazard rates
Thanks, assume we have two different groups with two different size and different P-values. Then how we can compare this groups HR with each other to see if it is significant or not? For example I have male and female groups for the same disease and the number of cases are different in both groups is it correct to compare their HRs?
Imagine linear increase in incidence of disease for two different conditions. Assume overall low incidence in the period of observation. Then the hazard ratio is about the same as the relative risk which is close to the odds ratio. No?
You are correct, not only this, the video also says later that you are still better off than having Vit D level of greater than 100, this line also is not in sync with what the data actually says. Otherwise this is a very nice video.
Good day doctor, I have a question; if I have a study comparing between a treatment group vs control group which yield a hazard ratio of 0.46, can i interpretate it as: (a) patient with the treatment group have are 54% less likely to suffered from primary end point as compared control or (b) patient with the treatment group have a 46% less likely to suffered from primary end point ?
For my understanding and revision. Risk Ratio = Group A Risk % / Group B Risk % Hazard Rate = # Death / # Population at time t Hazard Ratio = Group A Hazard Rate at time t / Group B Hazard Rate at time t Survival Rate = ∏ Survival Rate of Group A up to time t
Thank you! I was confused about how to apply the RR and HR . Now I'm cleared.
Your lecture is very helpful. You are a mavellous teacher.
Dr Patwari! you're an unbelievably amazing teacher! appreciate all your time and effort for all those precious videos
thx!
That was so helpful, just what I needed today on my masters in public health journey!
Amazing! Thank you very much. We have an exam tomorrow and our professor recommended that we watch this
This was a super helpful review of these concepts. Very easy to understand and follow for the non statistician. Loved your animations !
Thank you for that beautifully explained details!
saved a lot of time watching this video complementing with the text, thanks
Thank you so much Dr, you're a life saver
Great explanation! Although on 0:51 you say "edit that out". I assume you didnt want that in the final version
Oops! I forgot to edit that out!
@@oldblueday You sir, are forgiven. Really good vid. :) :)
@@oldblueday hello sir
I request help in one of medical journals
Thank you! Just one question. You say that Hazard ratio is the probability for an event to take place in a given time interval. In the table of Vitamin D levels and death that you use in the beginning of the video I can't see that the specific time interval for the hazard ratio is noted/specified, shouldn't a time intervall för the hazard ratio be specified then? (Maybe the time intervall was made clear in the text of the study?)
Well, so what does the hazard ratio that is written out in the beginning mean? What interval are we talking about? Isn't the point of Hazard ratio compared to RR to define a certain interval so we can see who is more likely to die in that interval? Otherwise why can't we just use RR? Shouldn't there be several hazard ratios presented, one for each interval??
6:27 You call the percentages ( 19% and 6%) 'hazard rates'. I'd guess the ratio then would be 16/9 (comparing the hazard rate). But this is not mentioned. Is the hazard ration the same as the hazard rate, or is it the ration of both? I also don't understand why they should be the same (I guess that's under the H0, no difference hypothesis). Still, nice video, very clear and (important) enjoyable.
Great Job, Dr. Patwari!!! May you possibly have any worked examples for Board exam purposes? Thank you
I absolutely hate biostat, but not when it's made this easy! Thanks!
Solute to you sir 🙌🏽🙌🏽🙌🏽🙌🏽
Magnificent 👍👍
Thanks a lot. Could you please add a video on likelihood ratios and pre-post test probabilities?
How do I get a P-value comparing 1-year survival rate between two groups? What method should I use and what variables should I use?
Clear explanation, thanks!
thank you doc!!
you are nicely stated the case. thanks
Could you please explain why your hazard ratios aren't exactly in the middle of the confidence intervals? Does it have to do with lognormal distributions?
This is very helpful. Thank you a lot. :)
great video! Thanks
thank you for the explanation:))), it was really helpful. one question though, what is the difference between adjusted and unadjusted hazard ratio?
I got the idea that hazard ratio time element is important. but I didn't get the idea of "the hazard ratio is 2.5 it means that in a particular given interval, one group has a 2.5% 2.5 times more likely chance of experiencing the event (in this case death) then the other group does." how can i know this particular time from the table??
Hi! Splendid presentation. Can you share the tool you were using to create this one ?
thanks a lot, great explanation
How to compute the hazard probability using survival estimate ? I have embedded this formula to calculate using cumulative baseline hazard but I am getting higher integer values for hazard rate(hazard probability) : 𝑆0(𝑡)=exp(−𝐻0(𝑡)) - extract cumulative baseline hazard ; ℎ(𝑡|𝑋)=ℎ0(𝑡)*𝑒𝛽𝑋 - and then hazard rate using baseline; however, I see very high hazard rates
Thanks, assume we have two different groups with two different size and different P-values. Then how we can compare this groups HR with each other to see if it is significant or not? For example I have male and female groups for the same disease and the number of cases are different in both groups is it correct to compare their HRs?
I would like you to show how to calculate hazard ratio in calculus term
Brilliant! Thnks!
Why not just call it risk ratio like in relative risks since it seems to be the same calculation?
what about COX REGRESSION MODEL??? explaination please
hi, may i know how to plot the coxph model with the kaplan meier survivor curve?
Imagine linear increase in incidence of disease for two different conditions. Assume overall low incidence in the period of observation. Then the hazard ratio is about the same as the relative risk which is close to the odds ratio. No?
You made a mistake at 2:55 right? You meant, it could be better to have .95 and worse to have 1.62 right? Am I the only one who noticed this?
Yeah, I thought I was the only one. I wonder if it was a mistake??? Could someone please confirm?
You are correct, not only this, the video also says later that you are still better off than having Vit D level of greater than 100, this line also is not in sync with what the data actually says. Otherwise this is a very nice video.
What does a HR of o.69 mean?
I love you! come teach in the Netherlands plz
Good day doctor, I have a question; if I have a study comparing between a treatment group vs control group which yield a hazard ratio of 0.46, can i interpretate it as:
(a) patient with the treatment group have are 54% less likely to suffered from primary end point as compared control
or
(b) patient with the treatment group have a 46% less likely to suffered from primary end point ?
For my understanding and revision.
Risk Ratio = Group A Risk % / Group B Risk %
Hazard Rate = # Death / # Population at time t
Hazard Ratio = Group A Hazard Rate at time t / Group B Hazard Rate at time t
Survival Rate = ∏ Survival Rate of Group A up to time t
honestly , you didnt explain well. i couldnt understand
Thanks a lot. this was helpful