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. Author manuscript; available in PMC: 2017 May 1.
Published in final edited form as: Environ Int. 2016 Feb 23;91:104–115. doi: 10.1016/j.envint.2016.02.014

Table 3.

Military service and amyotrophic lateral sclerosis in GENEVA.

Cases Controls IP-weighteda
Variable No. % No % OR 95% CI
Military branch of longest service
  Air Force (including Army Air Force) 128 21 201 21 0.94 0.65, 1.36
  Army 252 41 316 33 1.00 Referent
  Marines (including Merchant Marines) 54 9 74 8 0.72 0.45, 1.16
  Navy 140 23 183 19 0.86 0.60, 1.22
  Otherb 45 7 182 19 0.35 0.22, 0.54
  Missing 2 2
Number of military branches of service
  1 (Median = 1) 571 92 727 76 1.00 Referent
  2 (2) 44 7 197 21 0.34 0.20, 0.56
  > 2 (3) 6 1 32 3 0.16 0.06, 0.47
  Missing 0 2
  Trendc 0.36 0.24, 0.54
Officer or Warrant Officer
  No 517 84 743 78 1.00 Referent
  Yes 102 16 213 22 0.72 0.49, 1.06
  Missing 2 2
Years of military service
  ≤ 1 (0.50) 15 2 23 2 1.45 0.53, 3.95
  > 1–5 (3.00) 418 68 429 45 1.00 Referent
  > 5–10 (6.74) 59 10 181 19 0.46 0.29, 0.73
  > 10–15 (12.00) 26 4 38 4 0.40 0.20, 0.81
  > 15 (22.06) 101 16 287 30 0.53 0.37, 0.75
  Missing 2 0
  Trend (IQR = 16.91)c,d 0.59 0.43, 0.81
End of most recent period of military service (month/year)e
  ≤ 06/1950 (07/1946) 48 8 12 1 5.07 1.57, 16.41
  07/1950–01/1955 (05/1954) 56 9 29 3 6.07 1.55, 23.78
  02/1955–02/1961 (08/1957) 97 16 65 7 4.96 2.14, 11.49
  03/1961–07/1964 (01/1963) 44 7 35 4 4.98 1.28, 19.40
  08/1964–04/1975 (07/1970) 191 31 281 29 1.00 Referent
  05/1975–08/1980 (08/1978) 41 7 127 13 0.21 0.10, 0.48
  09/1980–07/1990 (03/1985) 54 9 170 18 0.41 0.19, 0.87
  08/1990–08/2001 (11/1995) 71 11 152 16 0.56 0.27, 1.17
  > 08/2001 (01/2006) 17 3 87 9 0.37 0.09, 1.53
  Missing 2 0
  Trend (20 years, 11.63 months)c,d 0.36 0.23, 0.56

Abbreviation: ALS, amyotrophic lateral sclerosis; ALSFRS-R, ALS Functional Rating Scale-Revised; BIRLS, Beneficiary Identification and Records Locator System; CI, confidence interval; GENEVA, Genes and Environmental Exposures in Veterans with Amyotrophic Lateral Sclerosis; IP, inverse probability; IQR, interquartile range; OR, odds ratio; VA, Department of Veterans Affairs.

a

Weighted for confounding (conditional on age [centered at age 60—the median age among controls-and modeled with linear and quadratic terms], use of the VA health care system, sex, and race/ethnicity), not missing baseline ALSFRS-R score (cases only: conditional on most recent ALS diagnosis category, symptom onset site, time from symptom onset to diagnosis [months; modeled with the natural logarithm of a linear term], and time from diagnosis to enrollment in the Registry [months; modeled with a restricted, quadratic spline with knots at 7.72, 13.24, 23.06, and 44.19 months based on percentiles of the distribution in the Registry cases not missing baseline ALSFRS-R score]), and participating in GENEVA (cases: conditional on race/ethnicity, being a current patient of a VA Medical Center, most recent ALS diagnosis category, symptom onset site, time from symptom onset to diagnosis [months; modeled with linear, quadratic, and cubic terms], time from diagnosis to enrollment in the Registry [months; modeled with a linear term], and baseline ALSFRS-R score [modeled with a restricted, quadratic spline with knots at 12, 34, and 44 based on percentiles of the distribution in GENEVA cases]; controls: conditional on year of birth [modeled with a restricted, quadratic spline with knots at 1920, 1947, and 1974 based on percentiles of the distribution in the BIRLS potential controls], use of the VA health care system, and their interaction). 95% CIs were calculated with robust variance estimates.

b

Includes Coast Guard (cases: n = 8; controls: n = 11), Activated National Guard (cases: n = 6; controls: n = 28), Activated Reserves (cases: n = 17; controls: n = 37), Inactivated National Guard (cases: n < 5f; controls: n = 30), Inactivated Reserves (cases: n = 9; controls: n = 73), Department of Defense (cases: n = 0; controls: n = 0), National Oceanic and Atmospheric Administration (cases: n < 5f; controls: n = 0), and Public Health Service (cases: n = 0; controls: n < 5f).

c

Used within-category medians that were calculated using all controls.

d

Scaled the OR to an IQR-unit increase in the exposure variable. IQRs were calculated using all controls.

e

Category boundaries aligned with the occurrence of the major wars (e.g., the Vietnam War occurred between August 1964 and May 1975) and followed Allen et al. (2008) and Schmidt et al. (2008).

f

Suppressed to preserve the confidentiality of study participants.