National Academy of Sciences-National Research Council Twin Registry (NAS-NRC Twin Registry), 1958-2013 [RESTRICTED] (ICPSR 36234)

Version Date: Nov 16, 2020 View help for published

Principal Investigator(s): View help for Principal Investigator(s)
Margaret Gatz, University of Southern California; David (David Alan) Butler, National Academies of Sciences, Engineering, and Medicine. Institute of Medicine

Version V6 ()

  • V6 [2020-11-16]
  • V5 [2017-06-29] unpublished
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NAS-NRC Twin Registry

In 1958, the Medical Follow-up Agency (MFUA) of the Institute of Medicine began a project to identify twins who had jointly entered military service during World War II. In the end, MFUA identified nearly 16,000 White male twin pairs born 1917-1927 in which both members had served in the military. These twins comprise the National Academy of Sciences-National Research Council World War II Twin Registry (NAS-NRC Twin Registry). This collection represents data from service records, a mailed questionnaire assessing zygosity, and repeating health surveys, including information on education, employment history, and earnings.

There are nine datasets associated with this restricted-use collection:

1) The Administrative dataset includes demographic, zygosity, service history, mortality, and questionnaire participation data;

2) The Service and Other Records dataset contains information collected from service records, physical exam data, cognitive test data, and dental records;

3) The Questionnaire 2 dataset consists of data collected in the first mailed questionnaire sent in 1965 about pain, illnesses, smoking habits, alcohol consumption, and employment;

4) The Questionnaire 3 dataset includes data from the baseline epidemiological questionnaire sent in 1974 about number and sex of children, religious attendance, education, income, and occupation;

5) Questionnaire 7, mailed in 1985, contains similar topics as in Questionnaire 2, and includes data about health conditions such as diabetes, as well as feelings about work and retirement;

6) Questionnaire 8 was mailed in 1998 was the third epidemiologic questionnaire. This dataset is comprised of overlapping topics with Q2 and Q7, and has additional data about feelings, prescription medications, activity levels, the Geriatric Depression Scale, and parental death status;

7) The NEO Personality Inventory dataset includes responses to the NEO Five-Factor Personality Inventory mailed in 2005-2006;

8) The Service and Death Records dataset (VDE access only) contains information about date and place of birth, state at induction, disciplinary measures during service, decorations received during service, indicator for those known to have been POWs, reason for separation from the military, age at death if died over age 90, and cause of death. Some of this information was obtained from the re-read of service records and is thus available only for a subset of 6357 men;

9) Diagnoses dataset (VDE access only) contains data about medical conditions diagnosed between 1935 and 1985 that were abstracted from a variety of medical records over the course of the study. The diagnoses were coded using the International Classification of Disease system (WHO, 2015).

Gatz, Margaret, and Butler, David (David Alan). National Academy of Sciences-National Research Council Twin Registry (NAS-NRC Twin Registry), 1958-2013 [RESTRICTED]. Inter-university Consortium for Political and Social Research [distributor], 2020-11-16.

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United States Department of Health and Human Services. National Institutes of Health. National Institute on Aging (R21 AG039572)


This collection is restricted-use. Users interested in obtaining these data from NACDA must complete the NAS-NRC Restricted Data Use Agreement form. Users can download this form from the download page associated with this dataset. Completed forms with original signature(s) should be emailed to

Inter-university Consortium for Political and Social Research

1958 -- 2013
1958, 1967 -- 1973, 1974, 1985, 1998, 2005 -- 2006
  1. The variable CASENO is used to link the nine datasets in this collection.

  2. The Service and Death Records dataset, as well as the Diagnoses dataset, are only available to users via the Virtual Data Enclave (VDE).


The purpose of this project was medical research and improved clinical care.

Initial data include information abstracted from VA and military service records, a mailed enrollment form (Q1), and zygosity as determined by anthropometric and fingerprint (with later DNA confirmation for a subsample). For a modest subset of individuals, there are Army or Navy General Classification Test scores from the time of induction as a measure of cognitive ability. An epidemiologic questionnaire (Q2) was sent 1967-1973 upon the individual's enrollment into the study. Subsequent questionnaires were mailed in 1974 (Q3), 1985 (Q7), 1998 (Q8), and 2005-2006 (NEO Five-Factor Personality Inventory), repeating the epidemiologic questions and including education, occupation, earnings, family composition, leisure activities, and personality. Other data have come primarily from computerized VA records, including benefits and disability and medical diagnoses from the period of service through 1984. Date and cause of death were obtained from VA records, death certificates, the National Death Index, and LexisNexis. Selected twins have participated in sub-studies where data include screening for cognition and various complex diseases, e.g., heart disease, Alzheimer's disease, Parkinson's disease, eye diseases; in-person medical examinations and resulting diagnoses; related risk and protective factors; and genotyping.

The National Academy of Science-National Research Council (NAS-NRC) cohort consisting of 15,924 twin pairs was assembled in the late 1950s within the Medical Follow-up Agency (MFUA) of the Institute of Medicine (IOM). All White male twins born 1917-1927 in which both members had served in the military (N = 15,924 pairs) were identified. The sample was identified by matching VA records with birth certificates for White male multiple births (from all states except Arizona, Connecticut, Delaware, Georgia, Maine, Missouri, Utah, Vermont, and the city of New Orleans). A cohort profile describing the study can be found at Gatz et al. (2014, doi: 10.1093/ije/dyu181).

Longitudinal: Panel

White male twins born 1917-1927 in the United States, both of whom served in the United States military.

Individual, Twin pair

There are 9 datasets associated with this collection; seven are restricted-use and are available to users after completing a Data Use Agreement (DUA); two will only be available via the Virtual Data Enclave (VDE): 1) Administrative File - 29 variables; 2) Service and Other Records - 81 variables; 3) Questionnaire 2 (1967) - 81 variables; 4) Questionnaire 3 (1974) - 100 variables; 5) Questionnaire 7 (1985) - 121 variables; 6) Questionnaire 8 (1998) - 223 variables; 7) NEO Personality Inventory (2005-2006) - 7 variables; 8) Service and Death Records [VDE access only] - 14 variables; 9) Diagnoses [VDE access only] - 382 variables.

Service record information is available for 99 percent of those identified through record matching. When contacted by mail to invite participation in the study, 69.8 percent responded; 7.9 percent were deceased. For subsequent epidemiological questionnaires, it is not always possible to construct a response rate, since the researchers lack complete information about who was sent the questionnaire. Please see the International Journal of Epidemiology paper for more detailed information.

Army General Classification Test (AGCT) / Armed Forces Qualification Test (AFQT) / General Classification Test (GCT); Framingham Type A scale at Q7; Geriatric Depression Scale (GDS) at Q8; NEO Five-Factor Personality Inventory in 2005-2006.



2020-11-16 An updated user agreement is being released.

2018-02-15 The citation of this study may have changed due to the new version control system that has been implemented. The previous citation was:
  • Gatz, Margaret, and David (David Alan) Butler. National Academy of Sciences-National Research Council Twin Registry (NAS-NRC Twin Registry), 1958-2013 [RESTRICTED]. ICPSR36234-v6. Ann Arbor, MI: Inter-university Consortium for Political and Social Research [distributor], 2020-11-16.

2017-06-29 The data for dataset 1 and 7 are being replaced. In dataset 1, the values for zygosity variables have been updated. In dataset 7, additional records have been added.

2016-07-27 The enclave data files (datasets 8 and 9) are being re-released in order to correct an access issue caused by ICPSR systems. No changes have been made to the data or documentation.

2016-06-24 The data for dataset 7 is being updated. The questionnaires for datasets 1 and 3-7 are being publicly released. In addition, the Codebooks for the enclave datasets 8 and 9 are being publicly released.

2016-01-29 Publicly releasing codebooks for datasets 1-7.

2015-11-06 The fully-processed collection is being released.


No weights have been constructed for these data.



  • The public-use data files in this collection are available for access by the general public. Access does not require affiliation with an ICPSR member institution.

  • One or more files in this data collection have special restrictions. Restricted data files are not available for direct download from the website; click on the Restricted Data button to learn more.