Skip to main content

Table 1 Characteristics of invited subjects, enrollees, and non-responders in the Millennium Cohort Study by panel (2004-2008)

From: The impact of deployment experience and prior healthcare utilization on enrollment in a large military cohort study

  Panel 2 (2004-2006)a Panel 3 (2007-2008)b
  Invitedd Enrolleese Non-Respondersf Invitedd Enrolleese Non-Respondersf
(N=149,503) (N=31,110) (N=118,393) (N=199,671) (N=43,440) (N=156,231)
Characteristicc n (%) n (%) n (%) n (%) n (%) n (%)
Deployment experienceg*       
  None 76,087 (50.9) 15,682 (50.4) 60,405 (51.0) 75,014 (37.6) 18,168 (41.8) 56,846 (36.4)
  Prior to enrollment only 18,757 (12.6) 3,994 (12.8) 14,763 (12.5) 46,037 (23.1) 9,268 (21.3) 36,769 (23.5)
  During enrollment only 37,236 (24.9) 8,282 (26.6) 28,954 (24.5) 45,921 (23.0) 9,580 (22.1) 36,341 (23.3)
  Prior to and during enrollment 17,423 (11.7) 3,152 (10.1) 14,271 (12.0) 32,699 (16.4) 6,424 (14.8) 26,275 (16.8)
Number of outpatient visitsh*       
  None 11,396 (12.6) 1,421 (7.6) 9,975 (13.8) 18,426 (12.1) 2,494 (7.2) 15,932 (13.6)
  1-3 visits 24,047 (26.5) 4,100 (22.0) 19,947 (27.7) 39,226 (25.8) 7,641 (22.2) 31,585 (26.9)
  4-12 visits 33,099 (36.5) 7,163 (38.4) 25,936 (36.0) 56,426 (37.2) 13,723 (39.8) 42,703 (36.4)
  >12 visits 22,164 (24.4) 5,962 (32.0) 16,202 (22.5) 37,724 (24.9) 10,590 (30.7) 27,134 (23.1)
Cumulative days hospitalizedh*       
  None 85,083 (93.8) 17,335 (93.0) 67,748 (94.0) 143,135 (94.3) 32,253 (93.6) 110,882 (94.5)
  1-2 days 2,770 (3.1) 696 (3.7) 2,074 (2.9) 4,242 (2.8) 1,148 (3.3) 3,094 (2.6)
  > 2 days 2,853 (3.1) 615 (3.3) 2,238 (3.1) 4,425 (2.9) 1,047 (3.0) 3,378 (2.9)
Any diagnosed mental disorderi       
  No 79,984 (88.2) 16,377 (87.8) 63,607 (88.3) 133,992 (88.3) 30,443 (88.4) 103,549 (88.2)
  Yes 10,722 (11.8) 2,269 (12.2) 8,453 (11.7) 17,810 (11.7) 4,005 (11.6) 13,805 (11.8)
Any reported injuryj*       
  No 64,912 (71.6) 12,911 (69.2) 52,001 (72.2) 112,173 (73.9) 24,768 (71.9) 87,405 (74.5)
  Yes 25,794 (28.4) 5,735 (30.8) 20,059 (27.8) 39,629 (26.1) 9,680 (28.1) 29,949 (25.5)
Sex*       
  Male 111,781 (74.8) 19,167 (61.6) 92,614 (78.2) 152,029 (76.1) 27,941 (64.3) 124,088 (79.4)
  Female 37,722 (25.2) 11,943 (38.4) 25,779 (21.8) 47,642 (23.9) 15,499 (35.7) 32,143 (20.6)
Age (years)*       
  17-20 49,372 (33.0) 9,317 (30.0) 40,055 (33.8) 35,767 (17.9) 6,005 (13.8) 29,762 (19.0)
  21-22 35,666 (23.9) 6,693 (21.5) 28,973 (24.5) 74,159 (37.1) 13,916 (32.0) 60,243 (38.6)
  23-24 24,936 (16.7) 5,248 (16.9) 19,688 (16.6) 41,549 (20.8) 9,108 (21.0) 32,441 (20.8)
  >24 39,529 (26.4) 9,852 (31.7) 29,677 (25.1) 48,196 (24.1) 14,411 (33.2) 33,785 (21.6)
Education*       
  Some college or less 131,935 (88.2) 25,752 (82.8) 106,183 (89.7) 179,919 (90.1) 36,287 (83.5) 143,632 (91.9)
  Bachelors + 11,347 (7.6) 4,291 (13.8) 7,056 (6.0) 14,344 (7.2) 5,856 (13.5) 8,488 (5.4)
  Unknown 6,221 (4.2) 1,067 (3.4) 5,154 (4.4) 5,408 (2.7) 1,297 (3.0) 4,111 (2.6)
Marital status*       
  Never married 110,876 (74.2) 21,597 (69.4) 89,279 (75.4) 136,727 (68.5) 26,839 (61.8) 109,888 (70.3)
  Married 35,688 (23.9) 8,708 (28.0) 26,980 (22.8) 59,564 (29.8) 15,574 (35.9) 43,990 (28.2)
  Divorced, separated, or widowed 2,604 (1.7) 711 (2.3) 1,893 (1.6) 3,380 (1.7) 1,027 (2.4) 2,353 (1.5)
  Unknown 335 (0.2) 94 (0.3) 241 (0.2) 0 (0.0) 0 (0.0) 0 (0.0)
Race/ethnicity*       
  White, non- Hispanic 99,362 (66.5) 22,176 (71.3) 77,186 (65.2) 138,261 (69.2) 31,363 (72.2) 106,898 (68.4)
  Black, non- Hispanic 23,060 (15.4) 3,612 (11.6) 19,448 (16.4) 26,888 (13.5) 4,900 (11.3) 21,988 (14.1)
  Asian/Pacific Islander 5,857 (3.9) 1,537 (4.9) 4,320 (3.6) 9,821 (4.9) 2,451 (5.6) 7,370 (4.7)
  Hispanic 16,995 (11.4) 3,142 (10.1) 13,853 (11.7) 18,926 (9.5) 3,407 (7.8) 15,519 (9.9)
  Other 2,260 (1.5) 601 (1.9) 1,659 (1.4) 5,775 (2.9) 1,319 (3.0) 4,456 (2.9)
  Unknown 1,969 (1.3) 42 (0.1) 1,927 (1.6) 0 (0.0) 0 (0.0) 0 (0.0)
Military pay grade*       
  Enlisted 139,848 (93.5) 27,482 (88.3) 112,366 (94.9) 187,964 (94.1) 38,455 (88.5) 149,509 (95.7)
  Officer 9,655 (6.5) 3,628 (11.7) 6,027 (5.1) 11,707 (5.9) 4,985 (11.5) 6,722 (4.3)
Service component*       
  Reserve/Guard 58,711 (39.3) 12,459 (40.0) 46,252 (39.1) 47,869 (24.0) 8,992 (20.7) 38,877 (24.9)
  Active-Duty 90,792 (60.7) 18,651 (60.0) 72,141 (60.9) 151,802 (76.0) 34,448 (79.3) 117,354 (75.1)
Branch of service*       
  Army 61,442 (41.1) 14,995 (48.2) 46,447 (39.2) 81,067 (40.6) 15,798 (36.4) 65,269 (41.8)
  Navy/Coast Guard 28,110 (18.8) 5,263 (16.9) 22,847 (19.3) 35,893 (18.0) 7,922 (18.2) 27,971 (17.9)
  Marine Corps 29,939 (20.0) 2,576 (8.3) 27,363 (23.1) 49,942 (25.0) 6,802 (15.7) 43,140 (27.6)
  Air Force 30,012 (20.1) 8,276 (26.6) 21,736 (18.4) 32,769 (16.4) 12,918 (29.7) 19,851 (12.7)
Military occupation*       
  Combat specialist 47,502 (31.8) 6,833 (22.0) 40,669 (34.4) 44,437 (22.3) 6,333 (14.6) 38,104 (24.4)
  Electronic equipment repairer 9,333 (6.2) 2,490 (8.0) 6,843 (5.8) 13,935 (7.0) 3,867 (8.9) 10,068 (6.4)
  Comm/intel 10,529 (7.0) 2,678 (8.6) 7,851 (6.6) 16,737 (8.4) 4,079 (9.4) 12,658 (8.1)
  Healthcare 9,809 (6.6) 3,444 (11.1) 6,365 (5.4) 14,144 (7.1) 4,477 (10.3) 9,667 (6.2)
  Other technical and allied 3,487 (2.3) 935 (3.0) 2,552 (2.2) 5,904 (3.0) 1,642 (3.8) 4,262 (2.7)
  Functional support/admin 17,841 (11.9) 4,721 (15.2) 13,120 (11.1) 28,018 (14.0) 7,589 (17.5) 20,429 (13.1)
  Electrical/mechanical equipment repairer 22,350 (14.9) 4,171 (13.4) 18,179 (15.4) 34,990 (17.5) 7,087 (16.3) 27,903 (17.9)
  Craft worker 5,398 (3.6) 1,034 (3.3) 4,364 (3.7) 7,032 (3.5) 1,330 (3.1) 5,702 (3.7)
  Service and supply 16,210 (10.8) 3,219 (10.4) 12,991 (11.0) 24,281 (12.2) 4,144 (9.5) 20,137 (12.9)
  Students, trainees, other 7,044 (4.7) 1,585 (5.1) 5,459 (4.6) 5,829 (2.9) 1,689 (3.9) 4,140 (2.7)
  Unknown 0 (0.0) 0 (0.0) 0 (0.0) 4,364 (2.2) 1,203 (2.8) 3,161 (2.0)
  1. *Chi-square test of enrollees vs. non-responders was significant at the P < 0.05 level for both panels.
  2. aThe Panel 2 enrollment cycle was from 1 June 2004 to 14 February 2006.
  3. bThe Panel 3 enrollment cycle was from 5 June 2007 to 31 December 2008.
  4. cCharacteristics were evaluated at the time each sample was drawn (October 2003 for Panel 2; October 2006 for Panel 3).
  5. dInvited subjects are all those approached regarding study enrollment who did not refuse to participate in the Millennium Cohort Study.
  6. eEnrolled subjects are all eligible, invited subjects who successfully completed a baseline questionnaire during the enrollment cycle.
  7. fNon-responders include all those who were approached but did not respond or complete a baseline questionnaire during the enrollment cycle.
  8. gAny deployment experience in support of the operations in Iraq and Afghanistan.
  9. hAny cause healthcare utilization in the 12 months prior to the first day of the enrollment cycle, among active-duty personnel only.
  10. iAny reported principal diagnosis for a mental disorder, as defined by ICD-9 codes 290-319, among active-duty personnel only.
  11. jAny reported principal diagnosis for an injury, as defined by ICD-9 codes 800-959, 990-999, among active-duty personnel only.