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New research provides evidence that the risk of developing amyotrophic lateral sclerosis, or ALS, varies depending on a veteran’s military branch and rank. The findings suggest that those who served in the Air Force, Navy, and Coast Guard, as well as military officers, tend to experience higher rates of the disease compared to Army veterans and enlisted personnel. The research was published in Neurology.
Amyotrophic lateral sclerosis is a fatal neurodegenerative condition that slowly destroys motor neurons, the nerve cells in the brain and spinal cord that control voluntary muscle movement. As these cells break down, people gradually lose their ability to walk, speak, eat, and eventually breathe. While genetic factors play a role in who develops ALS, researchers estimate that environmental factors account for a substantial portion of the risk.
Military service is one of the most consistently identified risk factors for the disease. For instance, a 2026 study using the national ALS registry indicated that military veterans not only have a higher risk of developing the disease but also tend to experience a shorter survival time after diagnosis compared to civilians. Despite this established link, scientists still do not know exactly what aspects of military life increase this risk.
The United States military is composed of different branches, each with distinct environments, missions, and occupational hazards. By looking at how ALS rates differ across these branches and ranks, scientists can begin to pinpoint the specific exposures, such as chemical solvents, intense physical exertion, or psychological stress, that might be driving the increased risk. The research was conducted by Andrea L. Roberts, Marc Weisskopf, and their colleagues at the Harvard TH Chan School of Public Health, who aimed to investigate these differences using an exceptionally large dataset of veteran health records.
“We have known for some 20 years that military veterans are at increased risk for ALS compared to non-veterans, but we still don’t understand why,” Weisskopf, a professor of environmental epidemiology and physiology, told PsyPost. “This work was a first step in trying to better understand that by seeing if there are differences in risk between different types of veterans. This kind of thing can help us start to narrow down to what specific things about military service might be increasing ALS risk.”
The researchers analyzed electronic health records from the Veterans Health Administration, focusing on veterans who received care between January 2000 and October 2024. To ensure they were looking at new cases of ALS, they only included veterans who had at least two years of medical history with the hospital system before any ALS diagnosis. The final sample was massive, including over 9.1 million men and nearly 785,000 women. Within this group, the researchers identified 13,935 men and 484 women who developed ALS.
The team categorized the veterans by their branch of service (Army, Navy, Air Force, Marine Corps, Coast Guard, or multiple branches), their rank (enlisted or officer), and the length of their military careers. The researchers then used statistical models to compare the rates of new ALS cases across these groups, adjusting for factors like age, racial identity, and Hispanic ethnicity. Men and women were analyzed separately because military jobs and the resulting environmental exposures often differ by sex.
The results indicated distinct patterns depending on the branch of service. Among men, Army veterans were used as the baseline comparison group. Compared to the Army, men who served in the Air Force had a 29% higher rate of developing ALS. Navy veterans showed a 15% higher rate, and Coast Guard veterans had a 26% higher rate. On the other hand, men who served in the Marine Corps had a 22% lower rate of ALS compared to Army veterans.
“The lower rate among the Marines was not so much a surprise in that it had been seen in many studies before, but those all had few Marines,” Weisskopf explained. “So seeing it in this much larger population really confirmed that finding and left that as a bit of a puzzle as to why they seem to be at lower risk.”
When looking at rank, the researchers found that officers experienced higher rates of ALS than enlisted personnel. Male officers had a 64% higher rate of ALS than male enlisted personnel. For women, a similar pattern emerged, with female officers showing a 72% higher rate of ALS than their enlisted counterparts. Differences between branches were most pronounced among younger veterans, those ages 17 to 61, and tended to shrink in the oldest age groups.
“The higher rate among officers was a bit of a surprise,” Weisskopf noted. “Because there are differences in ALS by branch and rank, it suggests that there is likely something specific to military experience. Given the higher risk among those in the Air Force, Navy, and Coast Guard, and officers we are considering how to probe those groups more specifically now.”
Despite these relative increases across certain branches and ranks, the researchers emphasized that the absolute risk to any individual remains low. “It’s important to realize that ALS is still relatively rare. So any single person’s overall risk is small, even if elevated because of military service,” Weisskopf said. “Nonetheless, it is hugely impactful for those who get it, so we want to figure out why some people get it and some don’t so we can both try and prevent occurrences and also better understanding how it develops can give us insight into possible therapeutic avenues.”
Surprisingly, the study found that a longer length of military service was associated with lower rates of ALS. This runs contrary to the idea that more time in the military means more exposure to risk factors. The authors suggest a few possible explanations for this pattern. Jobs with high exposure to risk factors might simply be associated with shorter service commitments.
Alternatively, veterans who serve longer might be more likely to seek treatment at private civilian clinics rather than veteran hospitals after retirement, meaning their ALS diagnoses would not appear in this dataset. The higher rates among Air Force, Navy, and Coast Guard veterans suggest that specific occupational hazards in those branches, such as exposure to jet fuel, aircraft exhaust, or radiation, might play a role in developing the disease. The higher risk for officers is also a point of interest, as enlisted personnel generally face more physical strain and chemical exposure.
Officers often experience different stressors and tend to have higher levels of education. Some previous studies have indicated that people with higher education are more likely to be diagnosed with ALS, which might partly explain the difference. If the risk is tied to unique features of an officer’s environment, identifying those factors could help protect future service members.
As with all research, there are a few things to keep in mind. Veterans generally qualify for veteran healthcare based on service-related disabilities or specific environmental exposures. If the same exposures that increase the risk of ALS also make someone more likely to use this healthcare system, this could skew the results. To limit this issue, the researchers required all participants to have been in the health system for years before their diagnosis.
Weisskopf also highlighted a specific caveat regarding the findings for the Marine Corps. “Maybe that lower rate among Marines may not necessarily mean they are truly at lower risk,” he pointed out. “There are epidemiological reasons why we might see that if in fact they are at higher risk but that higher risk happens sooner after their military service. This is just speculation at the moment, but we are trying to see if we can address that question.”
The study also faced missing data, with rank information unavailable for over 900,000 male veterans. Because ALS is a rare disease and women make up a smaller percentage of the veteran population, the small number of cases among women made it difficult for the researchers to draw firm conclusions about branch differences for female veterans, as many comparisons did not reach statistical significance. The researchers also lacked genetic data, though they noted it is unlikely that genetic differences alone could explain the specific patterns seen across branches and ranks.
Moving forward, the research team hopes to identify the exact occupational hazards involved. “We are trying to get more granular on the military experience than just branch and rank,” Weisskopf said. “It has turned out, though, to be much harder than we thought to link military service data (DOD) with post service health data (VA).”
The study, “Association of Military Branch and Rank With Amyotrophic Lateral Sclerosis Incidence Among United States Veterans,” was authored by Andrea L. Roberts, Alexandre D. Vilela Braga, Ian W. Tang, Ran S. Rotem, Lauren R. Moo, Donald R. Miller, Steven D. Shirk, and Marc G. Weisskopf.