OMOP/Documentation/CommonDataModel_Wiki_Files/StandardizedDerivedElements/COHORT_ATTRIBUTE.md

The COHORT_ATTRIBUTE table contains attributes associated with each subject within a cohort, as defined by a given set of criteria for a duration of time. The definition of the Cohort Attribute is contained in the ATTRIBUTE_DEFINITION table.

Field	Required	Type	Description
cohort_definition_id	Yes	integer	A foreign key to a record in the COHORT_DEFINITION table containing relevant Cohort Definition information.
subject_id	Yes	integer	A foreign key to the subject in the Cohort. These could be referring to records in the PERSON, PROVIDER, VISIT_OCCURRENCE table.
cohort_start_date	Yes	date	The date when the Cohort Definition criteria for the Person, Provider or Visit first match.
cohort_end_date	Yes	date	The date when the Cohort Definition criteria for the Person, Provider or Visit no longer match or the Cohort membership was terminated.
attribute_definition_id	Yes	integer	A foreign key to a record in the ATTRIBUTE_DEFINITION table containing relevant Attribute Definition information.
value_as_number	No	float	The attribute result stored as a number. This is applicable to attributes where the result is expressed as a numeric value.
value_as_concept_id	No	integer	The attribute result stored as a Concept ID. This is applicable to attributes where the result is expressed as a categorical value.

Conventions

• Each record in the COHORT_ATTRIBUTE table is linked to a specific record in the COHORT table, identified by matching cohort_definition_id, subject_id, cohort_start_date and cohort_end_date fields.
• It adds to the Cohort records calculated co-variates (for example age, BMI) or composite scales (for example Charleson index).
• The unifying definition or feature of the Cohort Attribute is captured in the attribute_definition_id referring to a record in the ATTRIBUTE_DEFINITION table.
• The actual result or value of the Cohort Attribute (co-variate, index value) is captured in the value_as_number (if the value is numeric) or the value_as_concept_id (if the value is a concept) fields.