Key Concepts About Finding Datasets

Publicly-Released Datasets

Throughout the years, NHANES datasets and related information have been released in a variety of formats and different media. However, since the late 1990s, all publicly available data and related documentation are released and updated in a centralized location: the NHANES website.

Datasets contain data for persons who participated in the selected survey. The National Health and Nutrition Examination Survey (NHANES) datasets are labeled by cycle year. The website contains the public-use data files for each of National Center for Health Statistic's national surveys starting with the initial National Health Examination Survey (NHES) I dataset up to the most current dataset. Codebooks and documentation are part of each data file. (For more experience on locating data files and related documentation, please see the Locate Variables module and the Download Data Files module.)

There are several pages of downloads to review.

• The Questionniares, Data Sets, and Related Documentation page lists all the survey cycles from the most recent to most historic, and includes the NHANES Analytic Guidelines, and the suggested citation for NHANES to use in publications.
• The survey cycle page (titled by the survey cycle, e.g., NHANES 2001-2002) contains documentation about the survey, documentation on how to use the data and links to each of the four component pages. It is divided into four sections:
  • Contents at a Glance, which has information about the survey in general terms
  • Contents in Detail, which has detailed descriptions about the different items used in the survey including survey
    questionnaires, manuals, brochures and consent forms
  • Using the Data, which has Analytic and Reporting Guidelines and documentation on how the data was released, and
  • Data, Documentation, Codebooks, SAS Code, which has links to the five component pages:
    • Demographics
    • Dietary
    • Examination
    • Laboratory
    • Questionnaire
• The component page (titled by the survey cycle and then the component name, e.g., 2001-2002 Demographics) links to the data files, documentation, and variable list for that component. The component name is listed with the corresponding links to its Documentation file (Docs) and Data file (Data).

This layout only applies to the most Continuous NHANES datasets starting from 1999. Datasets earlier than 1999 will have a different format and layout.

Non-Publicly Released Datasets

High quality data is released according to these guiding principles:

• as widely as practicable, 
• as soon as possible after data collection, and
• in as much detail as possible,

while maintaining survey participant confidentiality.

As a result, some variables or entire data files are not publicly released due to disclosure concerns, for example, geographic identifiers. These files are only available through the Research Data Center (RDC). You may review the Data Release and Access Policy for more information. For some non-publicly released data, the documentation, including a codebook with frequencies, is available to assist data users preparing proposals to use the Research Data Center.