BMC Public Health 2004, 4:27 http://www.biomedcentral.com/1471-2458/4/27 Table 3: Summary of self-reported symptoms/diseases among GWV by GWS status (ordered by frequency of reported ill health categories among GWS) (Continued) Cardiovascular disorders 90 (6.9) Genito-urinary system disorders 77 (5.9) Genital system & bladder problems4 46 (3.6) Kidney disease / symptoms 35 (2.7) Night sweats / excessive sweating / 77 (5.9) "fevers" Chest pains / tightness (not elsewhere classified) Auto-immune disease Allergies other than skin Cancer5 Accidental injury 37 (2.9) 31 (2.4) 19 (1.5) 14 (1.1) 344 (3.6) 238 (2.5) 150 (1.6) 101 (1.1) 185 (2.0) 136 (1.4) 197 (2.1) 61 (0.7) 128 (1.4) 237 (1.9) 143 (1.2) 79 (0.6) 68 (0.6) 49 (0.4) 64 (0.5) 136 (1.1) 42 (0.3) 146 (1.2) 3.8 (2.9–5.0)*** 2.1 (1.8–2.5)*** 5.3 (3.9–7.2)*** 6.1 (4.0–9.2)*** 4.4 (2.8–6.9)*** 2.3 (1.8–2.8)*** 2.7 (2.0–3.6)*** 1.9 (1.4–2.6)*** 13.7 (9.2–20.2)*** 4.7 (3.4–6.5)*** 5.2 (3.3–8.1)*** 2.8 (2.1–3.8)*** 2.7 (1.8–4.1)*** 2.2 (1.7–2.8)*** 5.1 (2.8–9.2)*** 2.3 (1.5–3.4)*** 0.9 (0.5–1.5) 1.1 (0.8–1.4) 56 (4.3) 253 (2.7) 87 (0.7) 5.5 (3.8–7.9)*** 3.3 (2.6–4.3)*** 1Subject can appear in the table as many times as they reported different symptoms. More than one symptom within a group in the same subject counted once only. Number of symptoms in sub-groups may not add up to group total if more than one symptom was recorded within the group for the same subject. 2Adjusted for age at survey, service and rank at time of Gulf war, serving status at time of survey, alcohol consumption and smoking. 3Not Otherwise Specified (NOS) 4Category includes those reporting 'burning semen' GWS 6 (0.5%); unsure-GWS 5 (0.1%); non-GWS 2 (0.0%) 5Includes all reported malignant neoplasms, plus all reported brain tumours, benign or malignant. * 0.01 < p < 0.05 ** 0.001 < p < 0.01 *** p < 0.001 swings, memory loss/lack of concentration and head- aches. In common with results from other studies of GWV [13,14,19,21], those who stated that they had Gulf War syndrome reported the same types of symptoms as all GWV, but reported them at higher frequencies, providing evidence against a unique syndrome. Study limitations In the absence of an official register or a mandatory health evaluation programme, obtaining accurate information from post-combat veterans is a difficult process and one which inevitably relies on self-reporting. This method of data collection introduces possible selection bias into a study. After adjusting for undelivered mail, response rates among men were 53% for GWV and 42% for NGWV [15]. Given the relatively low response rate, an intensive tracing study of non-responders was conducted to investigate possible selection bias. Data from the study indicated that the majority of reasons given for previous non-participa- tion were entirely unrelated to reproduction or Gulf War service. Ninety percent of the reasons given by both GWV and NGWV for earlier non-response related to such things as not remembering receiving a questionnaire, thinking they had sent it back, or general 'mistrust' of the MoD [15]. It might therefore be concluded that response bias relating to adverse health outcomes was not large in this study. In terms of suitable controls, an advantage of this study was the comparison of GWV with another military cohort. Comparisons with civilian populations may have been misleading as military recruitment involves medical and fitness screening. Furthermore, 'healthy warrior' bias (where veterans deployed to the Gulf might be healthier than those who were not deployed) [22-24] is unlikely to account for the findings in our study because the comparison group were broadly matched to the GWV on fitness to be deployed. A potential problem with any retrospective study design is recall bias. The questionnaire asked veterans to consider any new medical problems or changes in general health they had experienced since the end of the Gulf War, and this involved them recalling events that might have hap- pened up to seven or eight years in the past. During this time there has been much media speculation over Gulf War illness and this may have introduced recall bias and led to under- or over-reporting of certain symptoms. Gray et al have shown that participation in Gulf War health reg- istries is greatly influenced by media attention and is likely to be influenced by compensation issues. This was illustrated by increased enrollment during periods of high media interest in Gulf War issues [17]. A further limitation of this study concerns the lack of clinical validation of self- reported ill health. However, conducting clinical exami- Page 7 of 10 (page number not for citation purposes)