This capability is restricted to Project Owners.
XNAT's core data types are built to be extensible to reflect the shape and organization of your study data. The xnat:subjectData data type does not have many demographic fields available in it by default, but is easily extendable in your project. Here's how to do it.
Adding Data Fields to the Subject Data Type
1. Go to your project home page, and click on Manage Custom Variables.
2. Select Subjects as your data type to modify, then click Add a custom variable set.
3. Specify your data details. For each data field you add, you should specify why type of data you expect, and whether to restrict users to entering enumerated values.
If you want these custom data fields to be widely available in your XNAT, leave the "Project Specific" checkbox unchecked.
4. Click Save to save your changes. The page will refresh, and your new data type additions will be selected.
5. Click Done to apply your changes to your project.
Viewing and Editing Custom Subject Fields
Once you have applied a custom variable set to your Subject Data data type, the category of data will be immediately noted on your subject report pages and the default Subject Edit form. To add values, click on the Edit command in the Actions menu.