NHANES is the principal source of information on the measured health and Nutritional status of the civilian noninstitutionalized population of the United States. The main objective of the NHANES is to monitor the health and Nutritional status of the United States population through the collection and analysis of data on a broad range of health and nutrition topics. A major strength of this survey lies in the collection of physical measurements and laboratory specimens.

Sponsoring agency: National Center for Health Statistics, Centers for Disease Control and Prevention, U.S. Department of Health and Human Services

Data universe:

The non-institutionalized, civilian U.S. population

Disaggregated Asian and Native Hawaiian or Other Pacific Islander categories collected:

Are disaggregated Asian and Native Hawaiian or Other Pacific Islander data publicly available? NO

Measures available:

Sample size and unit of analysis:

In the 2017–March 2020 pre-pandemic data set there were 15,560 nationally representative Sample Participant interviews and 14,300 examinations.

Types of geography available to researchers: Geocoded NHANES data are available on the restricted use files via the Research Data Centers.

What data are available?

What is the difference between PUBLIC-USE and RESTRICTED-USE data files:

RESTRICTED-USE files include data that would be considered sensitive or potentially pose a disclosure risk in combination with other data due to rarity or small sample sizes. This includes levels of geography, finer levels of race and ethnicity classification, and more detail on other questions and measurements included in the public use file.

How to access the PUBLIC-USE data:

NHANES data files are available on the NHANES website.

1. Go to CDC.gov
2. Select "NCHS"
3. Select "NHANES": https://wwwn.cdc.gov/nchs/nhanes/Default.aspx

How to obtain permission to use the RESTRICTED-USE data:

Permission to use NCHS RESTRICTED-USE data is obtain through submission of a research proposal to NCHS's Research Data Center (RDC). For details, please visit www.cdc.gov/rdc.

Constraints surrounding access to RESTRICTED-USE data (e.g., citizenship requirements, cost, etc):

For access to RESTRICTED-USE data, researchers must have an approved proposal on file, pay user fees, complete training and administrative forms, and submit their output for a disclosure review.

Agency policy re. sample sizes/publishable estimates/data suppression standards:

NCHS staff are required to use the NCHS Data Presentation Standards for Proportions (CDC→NCHS→publications→Vital and Health Statistics→Series 2→No. 175) to publish statistically reliable estimates. Researchers outside of NCHS are highly encouraged to use these standards as well.

Information on when the data were collected/what time period could be examined using the data:

NHANES data have been collected dating back to 1960 as a periodic survey. In 1970 nutrition was added to the survey and the name changed from the National Health Examination Survey to the National Health and Nutrition Examination Survey. Since 1999 it became continuous with data released in 2-year cycles. For measurements included across the surveys, trends can be conducted, in some cases using adjustment equations to adjust for laboratory changes.

Where to find disseminated official estimates:

In numerous published reports on the NCHS website:

1. Go to cdc.gov
2. Type "National Center for Health Statistics" into the Search box
3. Select "NHANES – Publications and Products":
   https://www.cdc.gov/nchs/nhanes/nhanes_products.htm

Type of data (survey, program, admin etc.): Survey

Do the data include measures of citizenship, or are respondents limited by citizenship (i.e., only U.S. citizens are included in the data)? NHANES does not limit participation according to citizenship but has asked about citizenship as part of the survey questionnaire in the past. Currently NHANES does not ask about citizenship.

Analytic Considerations:

Analysis considerations for NHANES data are detailed in survey documentation and analysis guidelines on the CDC website:

1. Go to cdc.gov
2. Select "NCHS"
3. Select "NHANES"
4. Select "Survey Data and Documentation"
5. Select "Survey Methods": https://wwwn.cdc.gov/nchs/nhanes/analyticguidelines.aspx

An NHANES analysis tutorial is also available at https://wwwn.cdc.gov/nchs/nhanes/tutorials/default.aspx .