Seattle Epidemiologic Research and Information Center (ERIC)
Identification of Vietnam-Era Veteran Twins
Formation of the Vietnam-Era Twin Registry
During the early 1980s, the VET Registry was formed through a search of computerized records maintained by the Department of Defense (DoD) and supplemented by the Department of Veterans Affairs (VA) database files. The DoD estimated that roughly 5.5 out of the 9 million Vietnam era Veterans were included in their systems. With help from the DoD, a computerized record linking method was developed that identified pairs of records that were likely to be twins. The method that was used involved the following criteria: males, born between 1939 and 1957, served on active duty during the Vietnam era (the interval 1964-1975), same last name, different first name, same date of birth, and same first 5 digits of the Social Security number (Goldberg et al., 1993). In total 15,711 potential Vietnam era Veteran twin pairs were identified using the computerized records.
Who is in the Registry?
All military records of discharged Veterans are maintained at the National Personnel Records Center (NPRC) in St. Louis. The records of Veterans from the Vietnam era are all stored in hard-copy format and take up approximately seven shelf-miles of space. Within the hard-copy record for each Veteran is their place of birth and the full names of both parents. Twinship was confirmed when there was an exact match on place of birth and parental names. In total, 7,369 twin pairs (14,738 individuals) were confirmed from the initial pool of potential twins identified from the record matching. These twins form the core of the VET Registry.
The VET Registry also includes 2,251 presumed biological adult offspring of the twins (∼50% male and ∼50% female) and 1,336 biological, adoptive, and stepmothers of these offspring. The non-twin groups were added to the Registry in the late 1990s as part of a set of VET Registry family studies. The adult offspring were born between 1971 and 1992, and the mothers were born between 1951 and 1963.