First of all, there is no stupid question in OHDSI.
‘Cohort’ table is a kind of ‘result’ table from the analysis, which is not usually generated during ETL process.
Usually, OHDSI ecosystem generates a cohort table for each analysis (or research project).
The cohort definition of OHDSI is: ‘A cohort is a set of persons who satisfy one or more inclusion criteria (a phenotype) for a duration of time’.
Subject_id of cohort is usually identical to the person_id of PERSON table. Cohort_definition_id represents unique identifier for the cohort. And cohort_start/end_date represents a duration of time for the cohort.
I crear about Cohort table is generated from analytical process.
Let me ask an additional question.
I would like to separate the ID used in the analysis from the ID used in the practice.
In this case, when I derive the data from the EHR to the omop system, do I convert the ID of the clinical practice to the ID for analysis in person_id and store it?
Actually, I understood person_ID to be patient IDs used in hospital practice, so I thought the ID would change when deriving subject_id from person_id.
@somacells
Indeed, in most institutions, we assign an unique new ID to each patient for OMOP-CDM during conversion (or ETL), and not using EHR’s patient identifier to minimize security concern.