The authors "found that the PON1 genotype and hearing nerve agent alarms were independent and the findings robust to both measured and unmeasured confounding, supporting a mechanistic [gene–environment] interaction. ... Moreover, the change in the combined effect from one category to the next was significantly greater than the sum of the independent effects of the environmental exposure and the genotype". Although organophosphate pesticides could have triggered the nerve agent alarms in use at the time and contributed to neurotoxic symptoms similar to GWI, Haley et al. ruled out pesticides as a primary cause of GWI, citing that pesticide use was "ubiquitous long before the approximately 10,000 alarms began sounding at the start of the air campaign when Coalition bombing of Iraqi chemical weapon facilities released the fallout cloud that reached U.S. troop concentrations just as sarin was detected at multiple sites," while "the PON1 R isoenzyme is the more efficient detoxifier of most pesticides." Less likely causes
According to the VAs 2008 RAC report, "For several Gulf War exposures, an association with Gulf War illness cannot be ruled out. These include low-level exposure to nerve agents, close proximity to oil well fires, receipt of multiple vaccines, and effects of combinations of Gulf War exposures."
In 2014, the National Academy of Sciences Institute of Medicine (IOM)—contracted by the U.S. Department of Veterans Affairs for the task—released a report concluding that the creation of a new case definition for chronic multisymptom illness in Gulf War veterans was not possible because of insufficient evidence in published studies regarding its onset, duration, severity, frequency of symptoms, exclusionary criteria, and laboratory findings. Instead, the report recommended the use of two case definitions, the "Kansas" definition and the "Centers for Disease Control and Prevention (CDC)" definition, noting: "There is a set of symptoms (fatigue, pain, neurocognitive) that are reported in all the studies that have been reviewed. The CDC definition captures those three symptoms; the Kansas definition also captures them, but it also includes the symptoms reported most frequently by Gulf War veterans. "The Kansas case definition is more specific and may be more applicable for research settings, while the CDC case definition is more broad and may be more applicable for clinical settings. Classification
Medical ailments associated with service in the 1990–1991 Gulf War have been recognized by both the U.S. Department of Defense and the U.S. Department of Veterans Affairs.Before 1998, the terms Gulf War syndrome, Gulf War veterans illness, unexplained illness, and undiagnosed illness were used interchangeably to describe chronic unexplained symptoms in veterans of the 1991 Gulf War.