Gulf War Illness and the Health of Gulf War Veterans Scientific ...

might have had little first-hand knowledge at the time of exposure, such as exposures to depleted uranium
and CARC paint, were reported least reliably. 988,1165,1767
Questions about the accuracy of veterans’ self-reported exposures require that identified risk factors for
Gulf War illness be assessed and interpreted with caution. Errors resulting from misclassification can
produce both overestimates and underestimates of the degree to which a particular exposure is actually
associated with illness. It is useful to note that studies of both U.S. and U.K. Gulf War veterans have
found that the reliability of self-reported exposures was unrelated to veterans’ health status, that is,
symptomatic veterans report exposures with the same degree of reliability as healthy veterans. 988,1767,1804
This indicates a potential for “nondifferential” misclassification of exposures, that could lead to
underestimates of the degree of risk resulting from some Gulf War exposures, particularly those reported
less reliably.
Unlike exposures, Gulf War studies have generally found that veterans report medical conditions with a
high degree of reliability. 692,751,789,989 For example, medical record reviews for a subset of veterans
participating in the U.S. national survey of Gulf War era veterans indicated that self-reported conditions
related to clinic visits and hospitalizations were reported accurately 93 percent of the time. 751
Studies have assessed the impact of reporting biases on epidemiologic findings in Gulf War studies using
different approaches. 692,988,1088,1165 One recent study, for example, reported that veterans in VA’s national
survey who had been notified that they were potentially exposed to nerve agents following weapons
demolitions at Khamisiyah, Iraq, were no more likely to report symptoms, medical conditions, or
healthcare visits than other veterans. Investigators concluded that, contrary to expectation, veterans who
believed they may have been exposed to nerve gas showed no tendency to “over report” health
problems. 1165 A study of Gulf War veterans in the Pacific Northwest found that media coverage of both
the Khamisiyah weapons demolitions and studies showing adverse effects of Gulf War exposures had
very little impact on veterans’ reports of chemical agents and other exposures in theater. 988 Iowa
investigators reported that Gulf War veterans were no more likely to respond to health questions in a
socially desirable way than nondeployed era veterans. 692 And in a study of the Fort Devens cohort,
inclusion of a measure of recall bias in multivariable analyses had no impact on identified associations
between exposures and Gulf War illness. 1804
Taken together, such studies suggest that despite obvious concerns related to the potential effect of recall
bias on Gulf War studies, its actual impact does not appear to have been extensive enough to render study
results uninformative. Still, the potential for error introduced by recall bias and other sources of
information bias is an important reason for considering patterns of results provided by multiple studies,
rather than relying on individual studies, especially when assessing relationships between experiences in
theater and Gulf War illness.
Characteristics and Impact of Gulf War Illness: Epidemiologic Research • 35