Studies of U.S. Veteran Twins
Since the time of Sir Francis Galton, studies of human twins have provided material with which to study the relative effects of genetics and environment. When identical twins are more similar with respect to some characteristic than fraternal twins, this is taken as evidence of a genetic influence on a particular characteristic. In 1958, the Medical Follow-up Agency (MFUA) began a project to identify white male twins who had jointly entered military service during World War II. In the end, MFUA identified nearly 16,000 twin pairs in which both members had served in the military.
Certain baseline data were abstracted from VA and military records, an initial questionnaire was mailed to the twin pairs, and anthropometric and fingerprint data were used to determine zygosity (i.e., to differentiate identical from fraternal twins). Subsequent follow-up data have come primarily from computerized VA records and mail surveys.
Access to the Registry
Access to the NAS-NRC Twin Registry is available to qualified researchers whose use of the Registry is deemed appropriate by the Committee on Twins Studies. The committee evaluates proposals according to the principles outlined above and may request supplemental information or make recommendations about technical aspects of the proposed study. Access to the Registry is granted only upon approval by the Subcommittee.
Investigators are required to limit their contact with Registry subjects to that detailed in their application and to agree not to undertake any additional contact except upon submission and approval of a supplemental application. Initial solicitation of the twins is made under the Registry's auspices, and only if the twins consent to participate in a study may they be contacted subsequently by the investigators. The National Academy of Sciences' Institutional Review Board (IRB) reviews and approves all twin research projects. All information obtained from the twins becomes a part of the Registry and may be made available to future investigators.
The Registry has provided an important basis for epidemiologic and heritability studies since the late 1950's. The usefulness of the registry is now maximal because of the rapid accumulation of morbidity and mortality endpoints in this population of men aged 69 to 79. However, an estimated 500 men die annually. Half of the pairs are no longer intact due to deaths.
The Registry receives no funding for its core program, and investigators are therefore expected to contribute toward these expenses. The cost of accessing the data for secondary analysis is a one-time fee of $10,000.
Brief letters of interest outlining a proposed area of research in the Registry are welcomed and may be sent to:
David A. Butler, Ph.D.
Director, Medical Follow-up Agency
NAS-NRC Twin Registry
Institute of Medicine, National Academy of Sciences
500 5th Street, N.W.
Washington, DC 20001