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The Expectations from Health StudiesSummary of presentation by: Paper prepared from edited transcripts of the RMA Forum The Expectations from Health StudiesThis talk is about health studies and the way in which they may or may not be of use to the RMA and the SOP system. The first thing to note is that the compensation system in Australia depends upon causes of diseases as defined by exposures. It does not depend upon classes of veterans. In fact, factors in SOPs made on classes of veterans are not covered by the legislation. The RMA has had a lot of requests over the years to make factors for groups of veterans, everything from groups down to less than a dozen men, through to whole theatres. If we did go down that path, we would actually finish up with hundreds of factors based around increasingly smaller and smaller groups, and that's not what the parliament, to this point in time, has decided. One example is provided by the Korean War veterans' cancer study, which showed an excess of smoking related cancers. Although there is no factor for Korean War veterans, they can make claims under the SOP system. Korean Veterans who have lung cancer can claim under a number of factors that already exist in lung cancer - smoking, diesel fumes - just to name a couple. If they have cirrhosis of the liver, they can claim under the alcohol factor. It comes back to the point that not all people in a deployment have the same exposures. There is a tendency for a health study to assume that a particular group of soldiers, whether they be Korean veterans or whether they be a smaller group, have all had the same exposures when in fact they haven't. Furthermore, it is sometimes quite difficult to sort out even what the exposures were 50 years ago, or 20 years ago, let alone which individuals were exposed to which particular exposures. It has been our experience that quite often health studies have raised expectations that the RMA is in no position, legally, to meet. The current F-111 deseal/reseal study brings up - from looking at what we have received so far- it brings up another issue about exposures. For a significant proportion of the chemicals that appear to have been part of the exposure, there is no sound medical-scientific evidence, no published literature, about what the effects of those chemicals might be. Again, for the RMA, that's a blind alley because we can't guess at what might be the effects of a chemical. Occasionally, if a chemical were very closely related to a molecule that has been extensively investigated, we might be able to draw some conclusions about potential effects. Another issue that has come up in the Gulf War 1 study, is that the outcomes measured by the study don't fit the definition of "disease" in the legislation or, for that matter, don't fit the definition of "disease" in the standard medical text books. The Gulf War study turned up a constellation of symptoms but no specific identifiable disease. And looking at the F-111 study, it's clear that people have a lot of symptoms and they also sometimes appear to have signs, but unless there is a definable disease, legally we have no starting point. Those are two of the problems with retrospective health studies, the problem of measuring exposures and the problem of the sorts of outcomes that health studies sometimes produce. Retrospective studies depend to a significant extent on people's recall and there is really very little opportunity to measure exposures. It is not that the health studies are not as well done as possible, it is that the retrospectivity and the nature of the data preclude some of the outcomes that you would get from a hypothesis driven prospective study. The general principle is that retrospective studies often only really raise problems, they don't solve them. Another problem with health studies is the finding of many different symptoms, which could just be a chance finding or a finding of unknown significance. If you look at the general practices around Australia on any particular day, there's a percentage of Australians who go to see their GP, say 5%. Now, that 5% who go to see their GP on any one day, bring with them about a dozen different symptoms and many of them never get a diagnosis specifically attached to them. On that same day, 20% of the community had those same symptoms and did not go to a doctor. If you go to the next day, 5% go to their GP again, but it's a different 5%. When you're dealing with human beings and their symptoms, the facts of the matter are that many of the symptoms that human beings have mean nothing, because the next day they're gone and another group of people have got the same symptom. It raises a lot of false alarms, particularly if people have got a heightened susceptibility to observing their own symptoms. There can even be problems with abnormalities detected by laboratory tests. It is well-known that if you do blood tests on everybody in the room here, you find abnormalities by chance, and if you do that same level of blood tests a week or a month later, you get false positive results on a different group of the population. An enormous amount of health resources in this country is wasted following false trails of what are chance laboratory findings in somebody who has got absolutely nothing wrong with them. Laboratories in general have got a false positive rate, so by definition, some of the results you get out of a laboratory are going to be wrong. Some of the ones that are wrong are going to be high, by chance. These are the sorts of background issues that impact upon retrospective non-hypothesis driven studies. They raise problems that actually don't exist, and you finish up with these constellations of symptoms which often don't add up to anything more than what's going on in the average community, day in and day out. It is hard to untangle when you've got something real, and when you've got something that is just one of these false positives. In retrospective studies exposure to risks from medical interventions are often studied. In every situation in treating a patient, or deciding on a vaccination regime for children or soldiers or anybody else, you are balancing the risks against the benefits. All immunisation has a complication rate. Aspirin has a complication rate- if you take aspirin, you're more likely to die of haemorrhagic stroke than you are if you don't take aspirin. There is no medical intervention that does not have a risk. The safest and most cost effective medical intervention ever invented is still aspirin, in economic terms, but it still has a down side. It is important to compare the risk of intervention with what would have happened if there had been no intervention. Because the risks occurred a long time ago they can be difficult to assess. Many retrospective health studies - not just retrospective studies in veterans, but retrospective studies in general - are often under-powered. What happens is that even if you start with a large number, by the time you get down to specific disease entities, or specific findings, or specific syndromes, the number of people left in that category do not give you the statistical power to calculate a statistically significant outcome. When studying small groups another danger is that when the number of cases of a particular disease is measured, instead of finding three cases of cancer X, they find seven. That is two and a half times what is expected and it looks like something is really going on. What you don't know is that in the next 500 people, there are going to be no cases because the statistics will catch up and the rate will balance out over time. The lack of statistical power means that the results are unreliable, and could be purely due to chance. Some ethics committees actually view a study that has small sample size and therefore has low power as being unethical in its own right. They might produce a non-finding and create more questions than you actually answer. That is considered by some ethics committees who do their homework to actually be an unethical thing to ask people to approve. One of the other problems of health studies is that they aren't that, they are actually sickness studies. They ignore the fact that, quite often the group that is being studied has a number of things that positively affect their health. One of the concerns of public health practitioners about these sorts of studies is they have a great propensity to make a group of people who are well become sick, because they overlook the positive effects of whatever the exposures might have been. Those are the main issues that impact upon the RMA's ability to use retrospective studies, whether they be retrospective health studies of veterans; or whether they be retrospective studies of bus drivers in Denmark; or occupational studies of lead workers in factories. That is not to say that retrospective health studies are not capable of providing key information. A lot of the RMA's findings in health have come from retrospective studies when there has been no other option. The limitations- small sample sizes, poor exposure documentation and lack of a predefined hypothesis- restrict their usefulness. Certainly, retrospective studies will be the only way you're going to get efficient collection of information about rare forms of cancer or motor neurone disease or other diseases that don't occur very much. On the other hand, prospective studies give you the opportunity to study the symptomatology that you see in a reasonably short amount of time after deployment. The RMA is very pleased that Defence is moving towards being able to prospectively look at exposures of troops in the field. Some of our allies appear to be far ahead of us in doing it, and are actually plotting where each individual soldier was and his or her particular exposures. I think in the future, those sorts of prospective studies will actually be able to produce some outcomes which may well be more useful to the RMA than the retrospective studies have tended to be. Soldiers will be prospectively tagged for their exposures, not necessarily their deployments. That will mean that a soldier over a lifetime, or over his/her period of service, will build up an exposure profile which may not necessarily reflect the deployment arrangements. Scientifically that is a more powerful tool than trying to measure diseases by deployments because not every soldier on the same deployment has the same exposures. Also, soldiers in the current Defence Force will go on many deployments. I think when you look at exposures rather than geographic parts of the world or different particular conflicts, there are going to be a whole different set of questions and a whole different set of outcomes that potentially might be more useful in the future. Prospective studies can give us, in an evolving way, responsiveness to a whole different set of needs and ways of doing more. It is only through those types of studies that we will be able to discover the evolution of problems, whether they start as constellations of symptoms or whatever, and know if there is going to be a progression to illness and have the opportunity to influence that course in a more positive way. We also shouldn't forget that the most powerful use of this research is not looking at health effects or claims for compensation, but the question of duty of care to make sure that people are not exposed unnecessarily to harmful things during deployments.
This page last updated 22 March 2005. |
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