Association of Military Branch and Rank With Amyotrophic Lateral Sclerosis Incidence Among United States Veterans.

Abstract

BACKGROUND AND OBJECTIVES: Military service is one of the most consistent risk factors for the development of amyotrophic lateral sclerosis (ALS), but little is known about what aspects of military service matter. Understanding the distribution of ALS risk in military personnel may help identify key risk factors. We aimed to ascertain the association of United States (US) military branch and rank with incident ALS. METHODS: We conducted a longitudinal cohort study including all veterans with a Veterans Health Administration encounter from January 1, 2000, through October 1, 2024, and more than 2 years of follow-up. Incident ALS was identified through medical records. Exposures included military branch (Army, Navy, Air Force, Marine Corps, Coast Guard, or multiple branches), military rank (officer, enlisted, or both), and length of service. Risk was estimated with Cox proportional hazards models, controlled for age, adjusted for race/ethnicity, and stratified by sex. RESULTS: The analytic sample comprised 9,157,938 men (13,935 incident ALS cases, mean age = 56.9 years) and 784,941 women (484 cases, mean age = 42.4 at start of follow up). Among men, compared with service in the Army, service in the Air Force (hazard ratio [HR] = 1.29, 95% CI 1.23-1.35), Navy (HR = 1.15, 95% CI 1.10-1.20), and Coast Guard (HR = 1.26, 95% CI 1.06-1.50) was associated with higher rates of ALS and service in the Marines a lower rate (HR = 0.78, 95% CI 0.68-0.88). Officers had higher rates than enlisted personnel (men, HR = 1.64, 95% CI 1.53-1.74; women, HR = 1.72, 95% CI 1.31-2.27). Longer service was associated with lower rates of ALS. In age-stratified models, differences in hazard rates between Army veterans and Air Force, Navy, and Coast Guard veterans were greatest for the youngest men (17-61 years, HR range = 1.26 to 1.51) and smallest for the oldest (>75-104 years, HR range = 0.99 to 1.12). DISCUSSION: ALS rates varied considerably by branch and rank in the US military, with larger differences among younger veterans. Officers and those serving in the Air Force, Navy, or Coast Guard may incur exposure to military environments that increase risk of ALS. It is imperative to identify relevant exposures to reduce harm to service members and, potentially, civilians with similar exposures.