Cohort Attribute

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	FK Table	Description
cohort_definition_id	Yes	bigint	COHORT_DEFINITION	A foreign key to the record containing relevant Cohort Definition information.
subject_id	Yes	bigint	Any	A foreign key to the subject in the Cohort. For e.g., records from Person, Provider, Visit Occurrence, Visit Detail, or Care Site.
cohort_start_date	Yes	date		The date when the Attribute Definition criteria for the Person, Provider or Visit first match.
cohort_end_date	Yes	date		The date when the Attribute Definition criteria for the Person, Provider or Visit no longer match or the Attribute membership was terminated.
attribute_definition_id	Yes	bigint	ATTRIBUTE_DEFINITION	A foreign key to the record containing relevant Attribute Definition information.
value_as_number	No	numeric/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	bigint	CONCEPT	The attribute result stored as a Concept ID. This is applicable to attributes where the result is expressed as a categorical value.
last_updated_datetime	Yes	datetime		Initially this is the time the row was written to OMOP. If the row is subsequently updated, it then becomes the most recent update time.
deleted_datetime	No	datetime		NULL initially. Set to the time when the row was marked for deletion. A value in this column sent to the central data source will result in this row being deleted from the combined dataset.

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 e.g. age, BMI) or composite scales (for e.g. Charleson index).
• Cohort Attribute records must contain a Subject Id, which can refer to any table. The Cohort Definition will define the type of Subject through the subject_concept_id . Common domains for Subject are the tables PERSON, PROVIDER, VISIT_OCCURRENCE, VISIT_DETAIL, and CARE_SITE.
• 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 field value_as_number if the value is numeric, or value_as_concept_id if the value is a concept.