Table 1.
Characteristics of the NAS-NRC Twin Registry population
| Characteristics | Total registry (at induction) | Baseline (Q2)e | Q3 | Q7 | Q8 |
|---|---|---|---|---|---|
| 1967–73 | 1974 | 1985 | 1998 | ||
| Number of respondents | 31 848 | 14 299 | 4938 | 9475 | 6248 |
| (number of complete pairs) | (pairs = 15 924) | (pairs = 5126) | (pairs = 2469) | (pairs = 2722) | (pairs = 2174) |
| Age range, years | 15–33 | 40–56 | 47–57 | 57–70 | 70–82 |
| Mean age (SD), years | 19.8 (2.3) | 45.4 (3.9) | 51.1 (2.9) | 62.5 (3.0) | 74.4 (2.8) |
| Zygositya | |||||
| MZ | 37.5% | 44.2% | 50.3% | 45.5% | 46.4% |
| DZ | 47.6% | 52.5% | 47.2% | 49.5% | 46.5% |
| Unknown | 14.9% | 3.3% | 2.5% | 5.0% | 7.1% |
| Rank | |||||
| WW II officer | 8.1% | ||||
| WW II enlisted | 89.5% | ||||
| Korean War officerb | 0.1% | ||||
| Korean War enlistedb | 2.3% | ||||
| Branch | |||||
| Armyc | 58.9% | ||||
| Air Force | 4.7% | ||||
| Navy | 30.3% | ||||
| Marines | 4.6% | ||||
| Coastguard | 1.5% | ||||
| Education, mean (SD) years | 13.3 (3.1) | 13.7 (3.1) | |||
| Education, highest degree | |||||
| Bachelors | 17.6% | ||||
| Masters | 5.8% | ||||
| JD or LLBd | 1.8% | ||||
| MD or DDS | 1.9% | ||||
| PhD or ScD | 1.4% |
aZygosity is based on DNA markers where available.
bKorean War includes Korean War and later.
cArmy includes Army Air Force until September, 1947.
dJD, Juris Doctor; LLB, Legum Baccalaureus or Bachelor of Laws (but considered a graduate degree); MD, Doctor of Medicine; DDS, Doctor of Dental Surgery; PhD, Doctor of Philosophy; ScD, Doctor of Science.
eWe refer to the Qs by their original numbering by MFUA. Q1 (not shown here) was a request to enrol in the study. Q2 constituted the baseline data collection. Q3 was a follow-up focusing on education and work. Q4 (not shown here) was a request for permission to link to medical records. Q5 was part of the ancillary NHLBI study. Q6 has been lost to history. Q7 and Q8 were follow-up surveys replicating many of the questions asked at Q2.