I was wondering what is the best way to construct a general population cohort in the data after a certain year (e.g., number of adults in the database after 2010). I am looking into this in order to get prevalence estimates. I have tried definining the cohort based on observation period (since I know that this is supposed to specify the entry to the database) and condition/observation occurrence of any condition/occurrence; however, these led to very different results. It would also be good if you consider that I would later on use inclusion criteria with the disease-specifying concept sets.
Related to that - I am also wondering why defining the age in inclusion criteria vs in restriction of initial events lead to different results, when I limit the initial events as the earliest event. I guess there is something I conceptually do not understand regarding these crtieria, so any further insight would be appreciated.