National Health and Nutrition Examination Survey (NHANES), Demographic and Questionnaire Data, 2007-2008

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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 20072008 questions were also asked in NHANES II 19761980, Hispanic HANES 19821984, NHANES III 19881994, 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 2007-2008 wave, the NHANES includes 69 datasets. These 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, 2007-2008 (The base of the Demographic dataset + all data from medical examinations).

2. National Health and Nutrition Examination Survey (NHANES), Demographic & Laboratory Data, 2007-2008 (The base of the Demographic dataset + all data from medical laboratories).

3. National Health and Nutrition Examination Survey (NHANES), Demographic & Questionnaire Data, 2007-2008 (The base of the Demographic dataset + all data from questionnaires)

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 Web site.

Data File
Cases: 10,149
Variables: 801
Weight Variable: WTINT2YR, WTMEC2YR
Data Collection
Date Collected: January 2007 - December 2008
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 2007-2008, there were 12,946 persons selected for the sample, 10,149 of those were interviewed (78.4 percent) and 9,762 (75.4 percent) were examined in the MECs.
Modes of data collection include 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. In 2007-2008 a new sampling methodology was implemented. All Hispanics were oversampled, not just Mexican Americans. In addition, for each of the race/ethnicity domains, the 12-15 and 16-19 year age domains were combined and the 40-59 year age minority domains were split into 10-year age domains of 40-49 and 50-59. This has led to an increase in the number of participants aged 40 and older and a decrease in 12 to 19-year-olds from previous cycles. Lastly, pregnant women are no longer oversampled. Based on these changes, some variables have been modified from previous release cycles. 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.

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