Those veterans in whom a distinct diagnosis cannot be made are allocated to a separate group, that of 'unexplained illness' which ICD-9 categorises as 'signs, symptoms, and ill-defined conditions' (SSIDC). This is an extremely heterogenous group of often vague and common symptoms in which no objective clinical or laboratory findings are noted. It is possible that this group may include patients in whom later findings may make a specific diagnosis possible. This group of 'unexplained illness' should not be taken as evidence for the existence of a mystery illness or distinct Gulf War 'syndrome'. Many general medical patients attending outpatient clinics will have no specific diagnosis following examination and investigation.

A total of 284 veterans presenting for assessment, seven of whom were entirely well, were given a total of 403 diagnoses; 106 patients had more than one diagnosis, with 80 patients having two diagnoses, 25 patients having three diagnoses and one patient receiving five separate diagnoses. Using the above classification, the results, obtained in the group are as given in Table 2.

Table 2. Total Diagnoses in 284 Gulf War veterans

Minor physical illness is defined as conditions which are either self-limiting or easily managed and which pose no serious threat to life or health; major physical illness includes conditions which pose a serious threat to life and health. Examples of the former group include conditions such as irritable bowel syndrome, tension headache, proctitis and various of the dermatoses. The latter group of serious illness includes conditions such as myocardial infarction, cardiomyopathy, inflammatory bowel disease, various leukaemias, lymphoma and other solid tumours.

Another method of analysis these data is to use the ICD-9 group coding for infectious disease, neoplasms and major body systems. Our data analysed by ICD-9 coding is shown in Table 3.

Table 3. Frequency distribution of principal diagnosis in UK Gulf War Veterans by ICD-9 coding

PSYCHOLOGICAL ILLNESS

It can be seen from Table 2 that psychiatric conditions account for just over one third of all Gulf War illness, with post traumatic stress disorder (PTSD) contributing to almost one half of all psychiatric conditions. Psychiatric conditions are broken down into specific diagnostic groups in Table 4.

Table 4. Psychiatric diagnosis

All cases of PTSD were attributable to Gulf War service, although in six cases preceding service either in Northern Ireland or The Falklands, had played an important role in causation. Likewise depressive illness and adjustment reaction also seemed to be triggered by Gulf service, although half of these cases had left the army shortly after the Gulf War and the adjustment to civilian life may also have played a part in the onset of the illness. As far as the onset of PTSD is concerned, it does seem from this group that patients do not necessarily require to experience a life-threatening event themselves or to witness it in others, in order to develop PTSD.

SERIOUS PHYSICAL ILLNESS

The majority of cases with serious physical illness had been diagnosed before they attended the MAP. They attended to register their condition and to ask whether their condition had been caused by service in the Gulf. We did identify one case of ischaemic heart disease in an ex-soldier with aching in his arms and an abnormal ECG; he has subsequently had angiography. We have also diagnosed hypothyroidism in a serving solider who has since become symptom-free on replacement therapy.

Table 5. Most frequent complaints among 284 British Gulf War veterans

CFS AND SSIDC

The group comprising 'symptoms, signs and ill-defined conditions' and 'chronic fatigue syndrome' (CFS) make up the second largest presenting group, after psychological conditions. A great deal of Gulf War illness has many of the features of chronic fatigue and some of these patients are severely debilitated and unable to work or even manage household tasks. This group present the greatest problems because chronic fatigue is an ill-understood and controversial condition. There is no certain treatment and 'fringe medicine' abounds in this area. It is within this group that diagnoses such as Multiple Chemical Sensitivity Syndrome and Total Allergy Syndrome will be made by other practitioners who may see Gulf veterans.

Whereas some veterans in this group are severely debilitated, others have minimal symptoms and are able to work full time. Symptoms are not localised to one organ system and there is no characteristic rash, fever or consistent laboratory finding in this group. It is the clinical impression of the author that veterans in this group on both sides of the Atlantic have a similar 'clinical feel'.

The prevalence of CFS in the general population is uncertain ad to determine whether this condition is over-represented in those who saw service in the Gulf will be extremely difficult, nevertheless studies to measure this are planned. This group of patients need a great deal of support with their illness and in the case of some patients who are still serving, a period at the Rehabilitation Unit at Headley Court has been very useful. Here a type of cognitive behavioural approach to treatment has been used, but this is a time consuming and expensive method of treatment.

ANALYSIS OF SYMPTOMS

A striking characteristic of many veterans attending the MAP is the multiplicity of their symptoms. The most commonly occurring symptoms are as detailed below:

Fatigue

Although fatigue is the commonest symptom, occurring in over half of all veterans seen, only a minority with this symptom meet the criteria for a diagnosis of Chronic Fatigue Syndrome. In general population surveys, the incidence of fatigue has been variously estimated, but has been reported as high as 20% in a randomly screened population.

Musculoskeletal disorders

These disorders are common in any service population, particularly knee and low back problems. Although 35% complained of muscle and joint pains, in only a small group of these patients was it possible to diagnose a specific disorder.

Irritability

The high incidence of irritability reflects that one third of all veterans assessed show evidence of psychiatric disorder. Chronic pain and discomfort can both cause irritability, as can sleep disturbance, another common symptom in veterans. Sleep disturbance can sometimes be due to sleep apnoea and several veterans have been referred for sleep studies. These are widely carried out in the US and some subjects with 'unexplained illness' may in fact have sleep apnoea.

Memory loss

Complaints of short-term memory deficit are common, although on closer questioning most patients deny any problems resulting from this deficit. It is usually of the type, 'I went upstairs to fetch something and when I got there I couldn't remember what it was I had to fetch'. I have not seen any veteran who has had a cognitive deficit in association with this memory impairment. Many veterans with memory impairment have had MRI brain scans and all of these have been normal. Memory impairment is of course often associated with depression, anxiety and PTSD, in addition to other non-neurological medical conditions.

Breathlessness

Breathlessness is frequently complained of, often in association with tingling in the limbs. If respiratory disease is excluded in these patients then a diagnosis of hypervention should be considered. This condition often responds well to advice about the control of breathing.

HYPOTHESES TO EXPLAIN GULF WAR ILLNESS

There has been no shortage of hypotheses to explain the illness seen in Gulf War veterans. Environmental factors have been considered, for there is no doubt that many troops were exposed to an arduous and hostile desert environment with extremes of temperature, dust and flies. The popular misconception of a 'four day war' was very far from the truth for troops away from home for many months, uncertain of their return. The event present threat of biological and chemical attack, with the need to get in and out of Individual Protective Equipment, with its resulting physiological degradation, must have imposed constant physical and mental stress on personnel.

Smoke from oil-well fires was a hazard mentioned by many troops, although US studies suggest minimal health risk from this source. 3 , 4 The use of pyridostigmine bromide as nerve agent prophylaxis has also caused concern about subtle long term effects. This drug has been used in medical practice since the 1950s in very much larger doses than those used in prophylaxis. If there were long term effects consequent upon its use, it is very likely that these would have been noted by now. During Gulf deployment there was also widespread use of a whole range of agents such as DEET, chlorpyrifos, d-phenothrin, malathion, methomyl, lindane, pyrethroids, etc. It has been suggested that these agents, perhaps in combination with pyridostigmine, might have given rise to neurotoxic effects. These could appear as memory loss, mood changes, impaired performance and irritability. However, one would expect toxic effects to occur around the time of exposure and then improve with time. Delayed and long-term effects as reported by some veterans would be an unusual manifestation of toxicity. Delayed and long term toxic effects have so far not been substantiated by research on any groups of veterans.

Another area of confusion concerns the possibility that Iraq may have used chemical weapons or that toxic agents may have been released by allied bombing of Iraqi facilities. Many detection devices alarmed during the war with the result that many believed they were under chemical attack. This occurred because the devices were extremely sensitive and this sensitivity had only been obtained at the expense of some specificity. There is no documented Iraqi use of chemical weapons. The suggestion that bombing Iraqi facilities could have released agents which then drifted many miles downwind, causing long-term damage but no acute effects, is discounted by both clinical sense and practical experiment. 5 , 6

There is one illness in veterans which is unique to service in the Gulf and that is viscerotropic leishmaniasis. The US troops noted 31 cases of leishmaniasis in total and of these, 12 cases were of this previously unrecognised viscerotropic form. 7 All these cases were identified within 18 months of return from the Gulf and all had abnormalities, either on clinical examination or on laboratory testing. This condition does however remind us that new illnesses do appear from time to time and that we should always be aware of this possibility, 'fortune favours the prepared mind' (Louis Pasteur). Although the MAP has diagnosed several cases of Giardiasis and one case of gastrointestinal amoebiasis, no British veteran has been identified as having any form of Leishmaniasis.

The vaccination programme is sometimes held to be responsible for Gulf illness in that it may have produced chronic fatigue and debility when various vaccines were given over a relatively short time. This idea is not supported by follow-up studies of US military recruits and laboratory workers both of which groups have received multiple vaccination over a relatively short time period. 8

CONCLUSION

The self-selected group of veterans seen on the MAP, has a variety of illness, some of which is due to Gulf War service, eg PTSD; some of which may be related to Gulf War service, eg bronchial asthma; and some which is not related to Gulf War service. An example of illness in this latter group would be the appearance of a malignant tumour within a few months of returning from the Gulf. We know from tumour induction studies that tumours begin long before they are clinically detectable and in some unfortunate veterans who developed tumours after their return from the Gulf, tumour induction must have stated some time prior to deployment.

From our small database it would not appear that there is a unique cluster of symptoms which would suggest a new pattern of illness in veterans. I have demonstrated above that some symptoms are common to many veterans but these symptoms are common in any population and do not necessarily indicate underlying disease. We know from the aftermath of other conflicts that veterans tend to report more symptoms and ill health, 9 although few differences between them and control populations are found on examination. 10

It is extremely unlikely that such a wide range of illness as that described above could be due to a single cause, even if that single cause was a combination of factors. This whole area is made more difficult by the impossibility of establishing a single case definition for Gulf War illness. US studies which have now assessed more than 27,000 veterans have concluded that 'a single coherent syndrome cannot be defined, even though many illnesses reported by veterans might be attributable to Gulf War service'. In April 1994 the National Institute of Health Workshop Panel found that no single disease or syndrome was apparent, but found multiple illnesses with overlapping symptoms and causes. 11

It is apparent, even from these preliminary data, that the wide range of illnesses described above were not triggered by exposure to a single agent, for in most cases there is no evidence of any such exposure. In many cases where an exposure is claimed the symptoms and signs do not match the diagnostic criteria for such an exposure. The nonspecific, multi-system nature of many veterans' symptoms is compatible with many of the manifestations of psychological stress and I would suggest that not only is this important in well defined conditions such as PTSD, but is an important aetiological factor in a great deal of the less well-defined illness found in veterans.

FUTURE PROGRESS

The analysis of the MAP findings to date indicate a wide range of varying symptoms and illnesses, with no unique factors identified. There is a high incidence of psychological illness, although this is not surprising following such a conflict as the Gulf War. The $64,000 question is whether morbidity from other illnesses is increased in Gulf veterans. Epidemiological studies are being planned to answer this question. These studies are now in the hands of the MRC and we hope that workers in these fields will be able to make some use of the MAP database. We also plan to compare our data sets such as databases held by Defence Analytical Services Agency.

Finally, the MAP raises the questions of health surveillance following any future conflict. A major lesson learned has been the importance of good record-keeping; not only with regard to illness suffered in war but exposure to any environmental or occupational hazards. During future conflicts we will need to know the location of individuals at any time in order to determine these sort of exposures. It seems that the military medical services are ideally placed to carry out the task of post-conflict health surveillance.

ACKNOWLEDGEMENT

I would like to thank Colonel Jack Johnston L/RAMC who played a major role in the clinical assessment of the Gulf veterans described in the above study.

REFERENCES

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4. Report to Congress, United States Gulf Environmental Technical Assistance. Washington. DC: Gulf Task Force, US Environmental Protection Agency; 1991.

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10. The Centers for Disease Control Vietnam Experience Study: Health Status of Vietnam Veterans II: Physical Health. JAMA 1988: 259: 2708-2714.

11. Presidential Advisory Committee on Gulf War Veterans' Illnesses: Interim Report (Washington, DC: US Government Printing Office, February 1996).