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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.