Cohort Definition

The COHORT_DEFINITION table contains records defining a Cohort derived from the data through the associated description and syntax and upon instantiation (execution of the algorithm) placed into the COHORT table. Cohorts are a set of subjects that satisfy a given combination of inclusion criteria for a duration of time. The COHORT_DEFINITION table provides a standardized structure for maintaining the rules governing the inclusion of a subject into a cohort, and can store operational programming code to instantiate the Cohort within the OMOP Common Data Model.

More details about cohorts in The Book of OHDSI: https://ohdsi.github.io/TheBookOfOhdsi/Cohorts.html#Cohorts

Field	Required	Type	FK Table	Description
cohort_definition_id	Yes	bigint		A unique identifier for each Cohort.
cohort_definition_name	Yes	varchar(255)		A short description of the Cohort.
cohort_definition_description	No	text		A complete description of the Cohort definition
definition_type_concept_id	Yes	bigint	CONCEPT	Type defining what kind of Cohort Definition the record represents and how the syntax may be executed
cohort_definition_syntax	No	text		Syntax or code to operationalize the Cohort definition
subject_concept_id	Yes	bigint	CONCEPT	A foreign key to the Concept defining the domain of subjects that are members of the cohort (e.g., Person, Provider, Visit).
cohort_initiation_date	No	Date		A date to indicate when the Cohort was initiated in the Cohort table

Conventions

• The cohort_definition_syntax does not prescribe any specific syntax or programming language. Typically, it would be any flavor SQL, a cohort definition language, or a free-text description of the algorithm.
• The subject_concept_id determines what the individual subjects or entities of the Cohort consists of. In most cases, that would be a Person (patient). However, cohorts could also be constructed for Providers, Visits or any other Domain.