Military Service Prior to Amyotrophic Lateral Sclerosis Tied to Longer Survival

Military service prior to amyotrophic lateral sclerosis (ALS) onset is associated with longer survival, according to study results presented at the 2024 American Academy of Neurology (AAN) annual meeting, held from April 13 to 18, 2024, in Denver, Colorado.

Although military service has historically been associated with an increased incidence of ALS, the effects of lead exposure on ALS survival have not been parsed from the impact of military service on ALS survival.

Researchers at the Harvard TH Chan School of Public Health and the University of Miami investigated the relationship between military service and ALS survival in the context of occupational lead exposure. Clinical and occupational data from patients with ALS who were enrolled in the CReATe PGB study conducted between 2015 and 2019 were collected for this study. Lead exposure from military and civilian occupations was determined using a job-exposure matrix and the military-occupational-classification crosswalk. The primary outcome was survival, which was analyzed using Cox proportional hazard models that considered sex, age of onset, site of symptom onset, smoking, and body mass index as covariates.

A total of 135 patients (military veterans, 23; non-military veterans, 112) with ALS were included in the study, 38 of whom died or required permanent assisted ventilation (median survival, 3.6 years). While 14 veterans had military occupational lead exposure, 13 non-veterans had a lead-exposed civilian occupation.  

Compared with individuals with no history of military service prior to developing ALS, those with a history of military service prior to developing ALS survived longer (hazard ratio [HR], 0.59; 95% CI, 0.23-1.54). This effect was more pronounced after adjusting for occupational lead exposure (HR, 0.36; 95% CI, 0.13-1.00). Results were comparable when restricted to those without lead exposure (HR, 0.23; 95% CI, 0.03-1.70). Lead exposure was associated with shorter survival (HR, 3.25; 95% CI, 1.45-7.28).

“This association is independent of other prognostic factors and suggests ‘military service’ may be too broad to capture the variance of multiple exposures,” the researchers concluded.