Skip directly to search Skip directly to A to Z list Skip directly to navigation Skip directly to site content Skip directly to page options
CDC Home

Research Data Center

National Health Interview Survey (NHIS) Restricted Variables


If researchers interested in using NHIS data find that something asked on the questionnaires does not have a corresponding variable in the public use data set, that variable may be restricted. The following list is not exhaustive, but it provides examples of NHIS variables that are restricted.



Geography is most often used to add contextual data to NHIS data. The geocodes page lists what geographic codes are available for 1990-current NHIS.


Preliminary Quarterly Microdata Files  


Examples of Restricted Variables Used by Other Researchers

  • Country of Birth and Related Immigration Variables (Person File)
  • State and Year of Birth (Person File)
  • Industry and Occupation Codes (Person File before 1997, Sample Adult 1997-present)
  • Detailed Race and Hispanic Origin (Person File)
  • Exact Dates (e.g., date of birth in Person File)


Restricted and Public Use Variable Lists *

*All lists are sorted by question.

Detailed variable lists are not currently available for earlier years not shown. As they become available, they will be added to this page.

In order to find NIS Teen restricted variables, you will need to know the question number from the NIS Teen questionnaire to identify the comparable restricted variables.





Research Data Center

Contact Us:
  • National Center for Health Statistics
    3311 Toledo Rd, Suite 4113
    Hyattsville, MD 20782
  • The U.S. Government's Official Web PortalDepartment of Health and Human Services
Centers for Disease Control and Prevention   1600 Clifton Rd. Atlanta, GA 30333, USA
800-CDC-INFO (800-232-4636) TTY: (888) 232-6348 - Contact CDC–INFO
A-Z Index
  1. A
  2. B
  3. C
  4. D
  5. E
  6. F
  7. G
  8. H
  9. I
  10. J
  11. K
  12. L
  13. M
  14. N
  15. O
  16. P
  17. Q
  18. R
  19. S
  20. T
  21. U
  22. V
  23. W
  24. X
  25. Y
  26. Z
  27. #