stiffness, myalgia, polyarthralgia, numbness or tingling, headaches, and nausea), psychologic distress (feeling nervous, worrying, feeling distant or cut off, depression, and anxiety), and panic (anxiety attacks; a racing, skipping or pounding heart; attacks of chest pain or pressure; and attacks of sweating). They confirmed them in a separate factor analysis in the validation sample. They also conducted factor analysis in the nondeployed group and found the same three factors, which accounted for 29% of the variance. Thus, the study did not support the existence of a new syndrome. The authors noted the difficulty of attributing to a single condition the increased reporting of nearly every symptom in every bodily system. The strengths of this study included the size and diversity of its study population and the inclusion of nondeployed veterans. It also had a substantially higher participation rate (90.7%) than earlier studies.
Ismail and colleagues (Ismail et al. 1999) applied factor analysis to a large representative sample of UK veterans. They were able to identify three fundamental factors, which they classified as related to mood and cognition (headaches, irritability or outbursts of anger, sleeping difficulties, feeling jumpy or easily startled, unrefreshing sleep, fatigue, feeling distant or cut off from others, forgetfulness, loss of concentration, avoiding doing things or situations, and distressing dreams), the respiratory system (unable to breathe deeply enough, faster breathing than normal, feeling short of breath at rest, and wheezing), and the peripheral nervous system (tingling in fingers and arms, tingling in legs and arms, and numbness or tingling in fingers or toes). The pattern of symptom reporting by Gulf War veterans differed little from the patterns reported by Bosnia and Gulf War-era comparison groups, although the Gulf War cohort reported a higher frequency of symptoms and greater symptom severity. The UK authors interpreted their results as arguing against the existence of a unique Gulf War syndrome. Strengths of the study were its two comparison groups and its ability to compare how well its three-factor solution fit its Bosnian and nondeployed (“era”) cohorts. As with the study by Haley et al. (1997b, see below), however, a lower-than-ideal response rate of 65% may have introduced selection bias.
In a population-based study of all Australian Gulf War veterans, Forbes and colleagues (Forbes et al. 2004) applied factor analysis to findings from a 62-item symptom questionnaire. Symptom reporting was ordinal: “none”, “mild”, “moderate”, and “severe”. Three factors were found that accounted for 47.1% of the variance: psychophysiologic distress (23 symptoms), cognitive distress (20 symptoms), and arthroneuromuscular distress (six symptoms). They were broadly similar to factors in previous analyses and were the same as factors found among nondeployed Australian veterans. However, although the prevalence was similar among deployed and nondeployed veterans, factor scores were higher among the deployed than among the nondeployed. That indicates greater severity of symptoms. The authors concluded that there was no evidence of a unique pattern of self-reported symptoms in deployed veterans. One limitation of this study is that most members of the Australian cohort were from the Navy, so its generalizability to services and personnel from other countries, particularly the United States, may be limited. Nonetheless, its inclusion of all Australian Gulf War veterans and a stratified random sample of nondeployed Gulf War-era Defence Force personnel eliminated the potential for selection bias that other studies had more difficulty in controlling. It is also valuable in setting a baseline of unexplained illness as an effect of deployment itself without the overlay of direct combat and environmental exposures more commonly encountered on land.