Table 1.
Characteristics of early refusers, early consenters, and late/non-responders for enrollment into the Millennium Cohort Study
| Early Refuser† | Early Consenter‡ | Late/Non-responder§¶ | ||||
| N | % | N | % | N | % | |
| Sex | ||||||
| Male | 537 | 76.3 | 15,283 | 70.0 | 147,497 | 76.9 |
| Female | 167 | 23.7 | 6,537 | 30.0 | 44,370 | 23.1 |
| Age quartile (years) | ||||||
| 17–23 | 88 | 12.5 | 2,994 | 13.7 | 47,596 | 24.8 |
| 24–29 | 106 | 15.0 | 3,761 | 17.2 | 46,958 | 24.5 |
| 30–37 | 178 | 25.3 | 6,186 | 28.4 | 51,107 | 26.6 |
| ≥38 | 332 | 47.2 | 8,879 | 40.7 | 46,206 | 24.1 |
| Education | ||||||
| No high school diploma | 22 | 3.1 | 1,330 | 6.1 | 14,961 | 7.8 |
| High school graduate | 187 | 26.6 | 8,436 | 38.7 | 96,903 | 50.5 |
| Some college | 211 | 30.0 | 5,723 | 26.2 | 46,783 | 24.4 |
| College graduate | 147 | 20.9 | 3,874 | 17.7 | 22,953 | 12.0 |
| Advanced degree | 137 | 19.4 | 2,457 | 11.3 | 10,267 | 5.3 |
| Marital status | ||||||
| Married | 492 | 69.9 | 14,074 | 64.5 | 103,076 | 53.7 |
| Not married | 212 | 30.1 | 7,746 | 35.5 | 88,791 | 46.3 |
| Race/ethnicity | ||||||
| White non-Hispanic | 543 | 77.1 | 16,294 | 74.7 | 124,676 | 65.0 |
| Black non-Hispanic | 55 | 7.8 | 2,441 | 11.2 | 36,713 | 19.1 |
| Hispanic | 31 | 4.4 | 1,170 | 5.4 | 14,245 | 7.4 |
| Asian/Pacific Islander | 64 | 9.1 | 1,474 | 6.7 | 11,778 | 6.2 |
| American Indian | 6 | 0.9 | 194 | 0.9 | 1,731 | 0.9 |
| Other | 5 | 0.7 | 247 | 1.1 | 2,724 | 1.4 |
| Service branch | ||||||
| Army | 201 | 28.6 | 9.907 | 45.4 | 86,120 | 44.9 |
| Air Force | 326 | 46.3 | 6,849 | 31.4 | 55,576 | 29.0 |
| Navy | 146 | 20.7 | 3,809 | 17.5 | 35,313 | 18.4 |
| Marine Corps | 21 | 3.0 | 982 | 4.5 | 12,635 | 6.6 |
| Coast Guard | 10 | 1.4 | 273 | 1.2 | 2,223 | 1.1 |
| Duty status | ||||||
| Active duty | 313 | 44.5 | 9,734 | 44.6 | 103,069 | 53.7 |
| Reserve/National Guard | 391 | 55.5 | 12,086 | 55.4 | 88,798 | 46.3 |
| Previous deployment experience# | ||||||
| Non-deployed | 502 | 71.3 | 15,873 | 72.7 | 134,177 | 69.9 |
| Deployed | 202 | 28.7 | 5,947 | 27.3 | 57,690 | 30.1 |
| Occupational category | ||||||
| Electrical/mechanical | 80 | 11.4 | 2,923 | 13.4 | 31,798 | 16.6 |
| Combat specialists | 169 | 24.0 | 4,281 | 19.6 | 40,325 | 21.0 |
| Electronic equipment repair | 73 | 10.4 | 1,837 | 8.4 | 15,388 | 8.0 |
| Communications/intelligence | 39 | 5.5 | 1,481 | 6.8 | 12,827 | 6.7 |
| Health care specialists | 67 | 9.5 | 2,601 | 11.9 | 15,794 | 8.2 |
| Other technical & allied specialists | 12 | 1.7 | 580 | 2.7 | 4,722 | 2.4 |
| Functional support specialists | 158 | 22.4 | 4,562 | 20.9 | 34,713 | 18.1 |
| Craft workers | 23 | 3.3 | 700 | 3.2 | 6,852 | 3.6 |
| Service and supply handlers | 48 | 6.8 | 1,854 | 8.5 | 17,212 | 9.0 |
| Trainees, other | 35 | 5.0 | 1,001 | 4.6 | 12,236 | 6.4 |
** First enrollment into the Millennium Cohort Study.
† Early refusers are invitees who communicated their unwillingness to participate in the study prior to 01 September 2001.
‡ Early consenters are invitees who completed an online or paper survey prior to 01 September 2001.
§ Late/non-responders are invitees who responded after 01 September 2001 or failed to respond in any manner.
¶ Differences between early refusers, early consenters, and late/non-responders were tested with the Pearson chi-square test of association. All p values were < 0.001.
# Previous deployment experience to southwest Asia, Bosnia, or Kosovo between 1998 and 2001.