National Health and Nutrition Examination Survey (NHANES), Demographic and Examination Data, 2005-2006

The National Health and Nutrition Examination Surveys (NHANES) is a program of studies designed to assess the health and nutritional status of adults and children in the United States. The NHANES combines personal interviews and physical examinations, which focus on different population groups or health topics. These surveys have been conducted by the National Center for Health Statistics (NCHS) on a periodic basis from 1971 to 1994. In 1999, the NHANES became a continuous program with a changing focus on a variety of health and nutrition measurements which were designed to meet current and emerging concerns. The sample for the survey is selected to represent the U.S. population of all ages. Many of the NHANES 2007-2008 questions also were asked in NHANES II 1976-1980, Hispanic HANES 1982-1984, NHANES III 1988-1994, and NHANES 1999-2006. New questions were added to the survey based on recommendations from survey collaborators, NCHS staff, and other interagency work groups. Estimates for previously undiagnosed conditions, as well as those known to and reported by survey respondents, are produced through the survey.

In the 2005-2006 wave, the NHANES includes over 100 datasets. Most have been combined into three datasets for convenience. Each starts with the Demographic dataset and includes datasets of a specific type.

1. National Health and Nutrition Examination Survey (NHANES), Demographic & Examination Data, 2005-2006 (The base of the Demographic dataset + all data from medical examinations).

2. National Health and Nutrition Examination Survey (NHANES), Demographic & Laboratory Data, 2005-2006 (The base of the Demographic dataset + all data from medical laboratories).

3. National Health and Nutrition Examination Survey (NHANES), Demographic & Questionnaire Data, 2005-2006 (The base of the Demographic dataset + all data from questionnaires)

Not all files from the 2005-2006 wave are included. This is for two reasons, both of which related to the merging variable (SEQN). For a subset of the files, SEQN is not a unique identifier for cases (i.e., some respondents have multiple cases) or SEQN is not in the file at all. The following datasets from this wave of the NHANES are not included in these three files and can be found individually from the NHANES website at the CDC:

Examination: Dietary Interview (Individual Foods -- First Day)
Examination: Dietary Interview (Individual Foods -- Second Day)
Examination: Food Frequency Questionnaire -- DietCalc Output
Examination: Physical Activity Monitor
Questionnaire: Dietary Supplement Use -- Ingredient Information
Questionnaire: Dietary Supplement Use -- Supplement Blend
Questionnaire: Dietary Supplement Use -- Supplement Information
Questionnaire: Dietary Supplement Use -- Drug Information
Questionnaire: Dietary Supplement Use -- Participants Use of Supplement
Questionnaire: Physical Activity Individual Activity File
Questionnaire: Prescription Medications

Variable SEQN is included for merging files within the waves. All data files should be sorted by SEQN.

Additional details of the design and content of each survey are available at the NHANES website.

Data File

Cases: 10,348
Variables: 1,217
Weight Variable: WTINT2YR, WTMEC2YR

Data Collection

Date Collected: January 2005 - December 2006

Original Survey (Instrument)

NHANES website

Funded By

National Center for Health Statistics (NCHS)

Collection Procedures

The most recent series of data collection waves for NHANES began in 1999. Every year, approximately 7,000 individuals, of all ages, are interviewed in their homes and of these; approximately 5,000 complete the health examination component of the survey. The health examinations are conducted in mobile examination centers (MECs). The surveys examine a nationally representative sample of approximately 5,000 persons each year. These persons are located in counties across the United States, 15 of which are visited each year. For NHANES 2005-2006, there were 12,862 persons selected for the sample, 10,348 of those were interviewed (80.45 percent) and 9,950 (77.36 percent) were examined in the MECs. Modes of data collection across the NHANES waves have included audio computer-assisted self-interview (ACASI), computer-assisted personal interview (CAPI), computer-assisted self-interview (CASI), face-to-face interview, and on-site questionnaire.

Sampling Procedures

The NHANES survey design is a stratified, multistage probability sample of the civilian non-institutionalized United States population. The stages of sample selection are: (1) selection of Primary Sampling Units (PSUs) which are counties or small groups of contiguous counties, (2) segments within PSUs (a block or group of blocks containing a cluster of household), (3) households within segments, and (4) one or more participants within households. A total of 15 PSUs are visited during a 12-month time period. Please note that there are different target population groups for topics within and between questionnaire sections. Data users should review the survey questionnaire codebooks and frequencies by age to determine the target populations for each NHANES questionnaire section. Additional details of the design, content of each survey, and analytic guidelines are available at the NHANES Website.

Principal Investigators

United States Department of Health and Human Services

Centers for Disease Control and Prevention

National Center for Health Statistics

Related Publications

Users should periodically check the NHANES Website to determine if any new or revised data files have been released and if analytic guidelines have been updated. In addition, DHANES staff publishes authored/co-authored publications and post them on the website.