Open AccessMilitary service, deployments, and exposures in relation to amyotrophic lateral sclerosis survival
Author(s) -
John D. Beard,
Lawrence S. Engel,
David B. Richardson,
Marilie D. Gammon,
Coleen P. Baird,
David M. Umbach,
Kelli D. Allen,
Catherine L. Stanwyck,
Jean Keller,
Dale P. Sandler,
Silke Schmidt,
Freya Kamel
Publication year - 2017
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0185751
Subject(s) - medicine , proportional hazards model , hazard ratio , confounding , amyotrophic lateral sclerosis , veterans affairs , confidence interval , environmental health , demography , agent orange , selection bias , military service , military personnel , covariate , statistics , disease , pathology , archaeology , sociology , political science , law , history , mathematics
Background Military veterans may have higher rates of amyotrophic lateral sclerosis (ALS) mortality than non-veterans. Few studies, with sparse exposure information and mixed results, have studied relationships between military-related factors and ALS survival. We evaluated associations between military-related factors and ALS survival among U.S. military veteran cases. Methods We followed 616 medical record-confirmed cases from enrollment (2005–2010) in the Genes and Environmental Exposures in Veterans with Amyotrophic Lateral Sclerosis study until death or July 25, 2013, whichever came first. We ascertained vital status information from several sources within the Department of Veterans Affairs. We obtained information regarding military service, deployments, and 39 related exposures via standardized telephone interviews. We used Cox proportional hazards regression models to estimate hazard ratios (HRs) and 95% confidence intervals. We adjusted for potential confounding and missing covariate data biases via inverse probability weights. We also used inverse probability weights to adjust for potential selection bias among a case group that included a disproportionate number of long-term survivors at enrollment. Results We observed 446 deaths during 24,267 person-months of follow-up (median follow-up: 28 months). Survival was shorter for cases who served before 1950, were deployed to World War II, or mixed and applied burning agents, with HRs between 1.58 and 2.57. Longer survival was associated with exposure to: paint, solvents, or petrochemical substances; local food not provided by the Armed Forces; or burning agents or Agent Orange in the field with HRs between 0.56 and 0.73. Conclusions Although most military-related factors were not associated with survival, associations we observed with shorter survival are potentially important because of the large number of military veterans.