You are genius, ..this is exactly what I needed, explaining topics with relevant examples makes so much sense of what we are actually studying ! Thank you so much for putting up this video.
Rahul nice videos. I am working in cancer epi, and teaching population epidemiology. You did a nice job. If you don´t mind I will recommend your youtubes in case the students would like to hear an alternative way of explanation! Just one comment... in minute 4 you discuss the persons at risk, but you omit the person-time (you just take the number of persons). Why did you not take the time at risk during the 10 years into account in your explanation?
Thank you for these videos, I am currently working on an MPH and have been struggling with my intro Epi course this semester. These have been so helpful!
Very well simplified, however, I though the denominator for the incidence would have been 5 and not 6 considering that the 6th person developed cancer after the 10 year period...?
Hi Rahul, I am curious why you DIDN'T count the number of person years in your calculation of incidence in this video whereas in your last example (your other video) of incidence you did?
Sarah, Greetings. Yes, some conditions such as myocardial infarction, fracture, adverse reactions, etc may have multiple episodes occurring within the same individual. First, for us to consider multiple episodes within an individual, he/she must have full recovery between episodes. Once this criteria is fulfilled, the usual way of calculation is via person-duration or person-years. For instance, 18 myocardial infarctions (MIs) were experienced among 157 individuals followed up each for two years. In that arm, during a period of 314 person-years of follow-up, the rate is (18 divided by 314) = 0.057 per person-year or 5.7 per 100 person-years. The 18 MIs arose through 12 patients having single MIs and 3 patients each having 2 MI. So, to your query, if there are multiple cases occurring, yes - the incidence would go up.
dr patwari were do you get 0.66 i am preparing for usmle step 3 i find bio stats really tough i listen to all your tapes they are great can you please tell me how it is 0.66
@@sanadbenali6993 Greetings. Risk means probability of acquiring the condition and importantly must not have the condition in question at the start of the time frame. Six individuals at the start of the time frame, did not have the condition YET, so these six is calculated as the denominator irrespective of whether they end up with the condition.
@@albiner1999 how would you justify calculating the control as a at risk a guy never gets cancer even after years with followup which i think Is bad protocol that person is no longer in a study both the control and the guy who got cancer later would be a bad choice right?
Not having cancer within the specified time does not mean that they are not at risk, it just means that the disease has not yet occurred. I think 6 people were taken for this reason.
It's the time frame in which we are counting the risk, ....these people had the risk and caught the disease , both within the the time considered , .......in case if you say those who caught the disease in the given time (who previously were at risk before acquiring the disease) shouldn't be counted ...then you will end up counting only those people who are not affected by the disease , which in this example will be 1 ..and that would be a different entity
