Open Burn Pit Exposure Increases the Risk of Headache Disorders and Migraine in Veterans

A retrospective cohort study including almost 250,000 veterans showed that the risk was highest in those with the most exposure.

There is a growing body of evidence linking airborne hazards – any chemical, physical, or biologic agent from the surrounding environment that is inhaled – to a range of adverse health outcomes, including headache disorders and migraine. One potential contributor to these hazards is open burn pits, which the U.S. military has used since the Gulf War in the early 1990s as a way of disposing waste, potentially exposing men and women serving in the military to a variety of toxic compounds.

Despite this, there are no studies on whether there is an association between airborne hazard exposure and the onset of new headaches among active service members and veterans. But now, new research from Jason Sico, VA Headache Centers of Excellence National Program Office, Orange, Connecticut, US, and colleagues shows an association between open burn pit exposure and medically diagnosed headache or migraine.

Using data from the Veterans Health Administration (VHA), Department of Defense, and the Airborne Hazards and Open Burn Pit Registry, the investigators found that the odds of developing headache or migraine in some veterans increased by as much as 60% compared to veterans without such exposure. Moreover, the odds rose as burn pit cumulative exposure increased.

“Given the available data on long-term exposure and outcomes, it would be hard to design a better study,” said Andrea Portt, a PhD candidate from the University of Toronto, Canada, whose doctoral research focuses on the association between air pollution and migraine.

“Environmental factors and hazards affect a lot of us. But most of the work that’s been done looking at environmental exposures or air pollutants and headache, especially migraine, has been in the short-term, that is, looking at ER admissions within a few days of relatively higher air pollutant exposures,” according to Portt, who was not involved in the current work. (See a recent systematic review by Portt and colleagues on migraine and air pollution.)

The research appeared in the September 2024 issue of JAMA Network Open.

Establishing a linked dataset
The Airborne Hazards and Open Burn Pit Registry was established by the U.S. Department of Veterans Affairs in response to the U.S. Congress enacting Public Law 112-260 in 2013. The registry was set up to learn more about whether open burn pit exposure may contribute to long-term injury in current and former service members. The U.S. Congress directed the VHA to explore potential relationships between exposure to open burn pits and headache disorders.

In the current study, the researchers did so by linking the burn pit registry data to electronic health records kept by the Department of Defense and the VHA for nearly 270,000 current and former service members captured by the registry between April 1, 2014, and October 31, 2022. This approach allowed for determination of whether a service member had been exposed to an open burn pit, and if so, what level of exposure they had.

Medically diagnosed headache disorder or migraine, as confirmed by administrative codes entered into the electronic medical record, served as the study’s co-primary outcomes. Portt described the use of a doctor-confirmed diagnosis as a “really solid” choice, as relying solely on self-reported measures introduces the potential for bias.

A dose-response relationship
The participants included in the final sample of roughly 248,000 veterans were predominantly male (222,468; 89.9%) and served in the U.S. Army (150,842; 60.9%). Half of the sample (125,862; 50.8%) were medically diagnosed with at least one headache disorder, while a quarter (61,812; 25.0%) received a migraine diagnosis.

In terms of burn pit exposure, the largest proportion of participants had been exposed to an open burn pit and had open burn pit-related duties (139,658; 56.4%), while a much smaller proportion had not been exposed to an open burn pit and had no known duties related to the burn pit (2,241; 0.9%).

Veterans with the greatest amount of open burn pit exposure had the highest rates of developing any type of headache compared to veterans without any burn pit exposure (55.8% vs. 40.4%), an outcome that also held for migraine (28.7% vs. 18.2%).

Next, the investigators computed an odds ratio (OR) that would show the odds of headache/migraine based on the level of burn pit exposure. These exposure groups included veterans who were near a burn pit and had burn pit duties; those near a burn pit and unknown burn pit duties; those near a burn pit and no burn pit duties; and those not near a burn pit and no burn pit duties.

After controlling for a number of factors including age, sex, race, and ethnicity; the branch of the military in which the individual served; and the presence of a traumatic brain injury, the investigators found that veterans in the highest open burn pit exposure group (that is, veterans near a burn pit and with burn pit duties) had the greatest odds of having medically diagnosed headache (an OR of 1.59) or migraine (an OR of 1.60) compared to veterans without exposure (not near a burn pit and no burn pit duties). This meant that veterans with the highest exposure had roughly a 60% increased likelihood of experiencing headache or migraine.

However, all veterans who had some level of exposure to an open burn pit had increased odds of headache and migraine compared to those with no exposure. And, on a secondary outcome, those with the highest exposure had almost twice the odds of having self-reported disabling migraine.

There was also an association between cumulative exposure and the odds of being diagnosed with headache or migraine, with the two highest quartiles of cumulative exposure having the greatest increase in risk. That included those with 290 to 448 days of burn pit exposure (the second-highest quintile), where the ORs for headache or migraine were 1.20 and 1.19, respectively, compared to those without burn pit exposure. Those who had even more burn pit exposure – more than 448 days (the highest quintile) – had an even higher risk of headache (OR of 1.55) and migraine (1.48).

Portt told Migraine Science Collaborative that the findings were somewhat expected.

“You might say that it’s a stronger association than expected compared to other environmental air pollution studies, but those other studies were looking at citywide levels and different types of pollution,” she said.

“If you are working right beside an open burn pit, you’re going to be exposed to a wider variety of chemicals than you would in more general air pollution studies, and it’s going to be a lot more intense. So it makes sense that there’s a stronger association.”

Positive change
While the researchers controlled for the effects of as many factors as possible in their analyses, there were several key variables for which they could not control.

“There is no systemic environmental measure of toxic chemical exposure from military open burn pits. The toxin composition and amount of toxin entering the area are likely to vary across time, open burn pit sites, open burn pit size, and local weather conditions,” they wrote in their paper.

Fortunately, recognition of the health consequences of open burn pit exposure has already spurred action, with the U.S. Department of Veterans Affairs having previously announced that the Department of Defense has closed out most burn pits and plans are to close out the remaining ones as well.

“My hope is that this type of work continues and workers’ exposures during deployment continue to be improved in terms of safety and monitoring for other environmental exposures, which I’m sure there will be many remaining,” Portt told MSC.

“I think there’s a lot of hope in this area in much of the world,” she added. “There has been a lot of improvement in reducing air pollution over the past decade, and that’s work that will continue. People with headache disorders are probably already benefiting from that and will hopefully continue to benefit.”

Lincoln Tracy, PhD, is a researcher and freelance writer based in Melbourne, Australia.

Reference
Open burn pit exposure in headache disorder and migraine.
Sico et al.
JAMA Netw Open. 2024 Sep 3;7(9):e2431522.

Image credit: U.S. Department of Veterans Affairs.