NHANES III Genetic Data

Collection of DNA in NHANES III
Description of the Genetic Data Sets
Demographic Information
Available Genetic Data Sets
How to Access the Restricted Data Sets
How to Access the Anonymized Data Sets
Informed Consent
Contact Us

Collection of DNA in NHANES III

The National Health and Nutrition Examination Survey (NHANES) is a program of periodic surveys conducted by the National Center for Health Statistics (NCHS) of the Centers for Disease Control and Prevention (CDC). Examination surveys conducted since 1960 by NCHS have provided national estimates of the health and nutritional status of the U.S. civilian non-institutionalized population. To add to the large amount of information collected for the purpose of describing the health of the population, blood lymphocytes were collected in NHANES III in anticipation of advances in genetic research from participants aged 12 years and older and stored in liquid nitrogen as cell cultures immortalized with Epstein-Barr virus. DNA in the form of crude cell lysates was made available for approved research projects from phase-2 (1991-1994) participants. There have been three announcements for use of these specimens announced (Tuesday, June 1, 1999 [64 FR 29321] August 8, 2002 [67FR 51585] and January 13, 2006[71FR 2248]). Genetic data generated by these projects is submitted to the NCHS where they are stored upon successful completion of a three part quality control analysis.

The goals of NHANES are (1) to estimate the number and percentage of people in the U.S. population and designated subgroups with selected diseases and risk factors for those diseases; (2) to monitor trends in the prevalence, awareness, treatment and control of selected diseases; (3) to monitor trends in risk behaviors and environmental exposures; (4) to analyze risk factors for selected diseases; (5) to study the relation among diet, nutrition and health; (6) to explore emerging public health issues and new technologies; (7) to establish and maintain a national probability sample of baseline information on health and nutritional status.

The Third National Health and Nutrition Examination Survey (NHANES III) began in the Fall of 1988 and ended in the Fall of 1994. Survey data were collected and can be analyzed from two phases: Phase-1 was conducted from October, 1988 to October, 1991, and Phase-2 was conducted from October, 1991 to October, 1994. Both phases are nationally representative samples. Please reference our Analytic and Reporting Guidelines for details on the NHANES III survey design and analytic guidelines. Genetic data is only available for Phase-2 of this survey.

Description of the Genetic Data Sets

The genetic data available through the NCHS is from 7159 specimens collected during Phase-2 of the Third National Health and Nutrition Examination Survey (NHANES III). Linkage of the NHANES III phenotype data with this genetic information provides the opportunity to conduct a vast array of outcome studies designed to investigate the association of a wide variety of health factors with regard to genetic variation. This collection is an ongoing process and additional genetic variation information will become available every six months. The NHANES III genetic data sets contain information from laboratories that have analyzed DNA in the cell lysates derived from these participants. The majority of the data sets will be found in the category of restricted access although there are a small number of anonymized data sets.

Demographic Information

The NHANES III survey oversampled non-Hispanic Blacks and Mexican-Americans which yielded the following population frequencies for the samples used to generate the genetic data:

*The ‘Other’ category includes all Hispanics, regardless of race, who were not Mexican-American and also includes all non-Hispanics from racial groups other than white or black.

Available Genetic Data Sets

There are two classifications of NHANES III genetic data. Please click one of the links below to view the available data sets for either restricted or anonymized data.

Restricted Access Genetic Data Sets

Requires IRB approval of analysis proposal.

Linkable to most NHANES variables for analysis in our secure Research Data Center (RDC).

Currently, all analyses must be performed at our RDC at the National Center for Health Statistics in Hyattsville, MD. There is a fee for the use of this facility.

Anonymized Genetic Data Sets

Limited number of associated variables that have been anonymized so the data can no longer be linked to the public use files and therefore not linkable to other NHANES data.

Does not require IRB approval.

Does not require data analysis at the NCHS.

Data available upon request with a data use agreement.

How to Access the Restricted Data Sets

Proposals to analyze genetic data sets may be submitted to NHANESGenetics@CDC.gov. Proposals will be reviewed three times annually by our IRB. Submissions for secondary data analysis of restricted data sets are accepted in February, June and October. For additional information on submission guidelines, please see our Guidelines for Secondary Data Analysis of NHANES III Genetic Data.

How to Access the Anonymized Data Sets

Access to the anonymized data sets does not require IRB approval because they are no longer linkable to any other data sets. These data sets contain a set number of variables. For access to genetic data in this category, please contact us at NHANESGenetics@CDC.gov.

Informed Consent

Health information collected in the NHANES III is kept in strictest confidence. During the informed consent process, survey participants are assured that data collected will be used only for stated purposes and will not be disclosed or released to others without the consent of the individual or the establishment in accordance with section 308(d) of the Public Health Service Act (42 U.S.C. 242m). Although the consent form was signed by participants in the survey, and participants consented to storing specimens of their blood for future research, specific mention of genetic research was not included during NHANES III. Nevertheless, given the scientific importance of this resource, the CDC/NCHS Ethics Review Board (ERB) initially approved use of the DNA only if the samples were anonymized. The anonymization requirements proved to be restrictive and difficult to implement, therefore, in August, 2001 the CDC/NCHS ERB approved a revised plan for using these specimens based on the guidelines in the August, 1999 National Bioethics Advisory Commission (NBAC) report on the use of stored biological materials for research. This revised plan included a process that gives researchers the ability to obtain more information associated with specimens for protocols that are determined by the ERB to have minimal risk for harm to the participant. For those protocols that cannot be conducted under unlinked (or anonymous) conditions, but have been determined to involve minimal risk, the revised plan allowed for linking of the genetic laboratory results to the NHANES data through the NCHS Research Data Center. This process ensured that confidentiality of the subjects’ identity was maintained.

Contact Us

Please contact NHANESGenetics@CDC.gov with any questions regarding NHANES genetic data.