> ## Documentation Index
> Fetch the complete documentation index at: https://docs.metriport.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Population

> Base StructureDefinition for Population Type: A populatioof people with some set of grouping criteria.

## Properties

| Name | Required | Type | Description |
| - | - | - | - |
| id | No | string | Unique id for inter-element referencing |
| extension | No | [Extension](/medical-api/fhir/data-types/extension)\[] | Additional content defined by implementations |
| modifierExtension | No | [Extension](/medical-api/fhir/data-types/extension)\[] | Extensions that cannot be ignored even if unrecognized |
| age\[x] | No | [Range](/medical-api/fhir/data-types/range), [CodeableConcept](/medical-api/fhir/data-types/codeableconcept) | The age of the specific population |
| gender | No | [CodeableConcept](/medical-api/fhir/data-types/codeableconcept) | The gender of the specific population |
| race | No | [CodeableConcept](/medical-api/fhir/data-types/codeableconcept) | Race of the specific population |
| physiologicalCondition | No | [CodeableConcept](/medical-api/fhir/data-types/codeableconcept) | The existing physiological conditions of the specific population to which this applies |


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