Thanks @Gowtham_Rao for initiating the discussion on hypertension. Glad that we are talking about heart diseases on Valentines day 
One thing I am unclear about in this clinical description (and indeed most others), which I presume would fit under ‘prognosis’, is how to think about potential resolution of a condition, and whether this is expected or observable. In this example, we could consider hypertension as a chronic disease and assume its therefore a condition that continues indefinitely (so cohort end is end of observation period). But, that may be overly simplistic: generally, clinicians will advise lifestyle changes (diet and exercise) and some patients who control blood pressure in this manner may get to a point where they can stop treatment (or potentially never start). Same would go for t2dm, even though we generally think of that as a chronic disease with no end date. The first question in my mind, before looking in the data, is what is the clinical truth of the disease: is it truly chronic and unresolvable, or can it start and stop/ recur? Then, the follow up based on the data is: how do we model this clinical reality, given what is observable? I could imagine that we reach a conclusion that we cant find the proper cohort episodes with what data we have, but i dont want to confuse that with what should be a patients true time varying disease status.