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Health Effects of Vietnam ServiceDr. Eileen J. Wilson for Salem-News.com
Originally published in 2003.
(MELBOURNE) - AUSTRALIAN DEFENCE FORCE PERSONNEL participated in the Vietnam Conflict from 1962 to 1973. This was the most significant military commitment of Australian Forces since World War II, involving nearly 60000 personnel, of whom over 500 died during service and 3131 were severely physically wounded.
Service during the Vietnam conflict presented distinctive health challenges. The nature of the conflict meant that troops were under combat-like conditions for extended periods. Herbicides and pesticides were used extensively. The United States military sprayed more than 76000000L of herbicides over Vietnam in their Air Force Ranch Hand and Operation Trail Dust programs. 1
The herbicides were used to strip the jungle canopy in order to reveal enemy positions, as well as to destroy crops and clear the perimeters of US and allied base camps.
The most heavily used of these herbicides was agent orange, contaminated with 2,3,7,8- tetrachlorodibenzo-p-dioxin, a known toxic agent. Other chemicals used widely in Vietnam included other herbicides (paraquat and dimethylarsenic acid), pesticides (picloram and DDT), antimalarial drugs (dapsone) and solvents (toluene).The Far Right of the Republican Party is a coterie of Evangelists and traditionalists whose minds are imprinted with a fixed image, memory, opinion, or idea in such a vivid or lasting way as to make it virtually impossible for them to change or accept defeat gracefully. Wisconsin and Minnesota voters offer a case in point.
Since the Vietnam conflict, ex-Service organisations (ESOs) have maintained that Vietnam service adversely affected the health of veterans. Initial studies into the health of veterans done in the 1980s showed no excess risk attributed to their service. However, more recent studies have shown that Vietnam veterans have excess incidence and mortality rates from several conditions, such as cancers and heart disease. In addition, environmental and occupational studies on the toxic effects of chemicals of interest have been useful in assessing health risks of Vietnam service.
This article reviews Australian and overseas studies on the physical health effects of Vietnam service.
Several key studies on the health of Australian Vietnam veterans have been published since the Vietnam conflict and are summarised in the following sections. In addition, the Box details a comprehensive list of the government studies and peer-reviewed published papers concerning research into the physical health of Australian Vietnam veterans.
Australian Veterans Health Studies
In 1980 the Australian government commissioned the Commonwealth Institute of Health (now known as the Australian Institute of Health and Welfare, [AIHW]) to conduct a series of studies into the health of Vietnam veterans and their families. A retrospective cohort mortality study of 46166 Australian National Servicemen, Part 1 of the Australian Veterans Health Studies, was completed in 1984. 2 The study compared the mortality of National Service veterans who served in Vietnam to National Service personnel who remained in Australia. This study found no significant increase in mortality among veterans compared with non-veterans. Both veterans and non-veterans had significantly lower mortality rates than expected for a similarly aged cohort of Australian males.
A factor that may have influenced the results of this study is the healthy worker effect. 3 Military personnel are screened at recruitment and are generally fitter than the Australian population. Personnel with diseases from congenital anomalies, mental disorders, and endocrine, nutritional and metabolic diseases are ruled out in the screening process.
The healthy worker effect lasts for many years after service and it is not clear what the magnitude of this effect may be over time. 4,5
Dapsone was an antimalarial drug used by Army and land-based Navy personnel serving in Vietnam from 1968 until 1972. The AIHW examined the relationship between dapsone exposure, Vietnam service and cancer incidence among 115407 Australian Army personnel, 40274 Vietnam veterans and a comparison group of 75133 serving members. 6 Dapsone had been shown to be associated with toxicity in white blood cells and other adverse reactions, such as haemolytic anaemia and peripheral neuropathy.
Concerns were also raised about the possible carcinogenicity of this drug. The study compared cancer incidence among Regular Army and National Service veterans and non-veterans and also correlated cancer incidence with lifetime dose of dapsone received. The study concluded that there was no definite evidence for an association between dapsone exposure and overall cancer incidence. Nor was there definite evidence of association between Vietnam service and overall cancer incidence.
However, the study did describe a statistically significant increase in pancreatic, lung, and brain cancers among National Service veterans compared with National Service non-veterans. This association was not seen among all veterans or Regular Army veterans. As 29 different cancer sites were tested for significant association, the authors reasoned that the three cancers showing increased rates could be a statistical anomaly. In addition, the authors concluded that, given the follow-up period was at most 24 years, it was too early to expect a significant increase in rates of solid cancers.
Vietnam veteran mortality study
A second Vietnam veteran mortality study was completed in 1997. 5 This study compiled a comprehensive nominal roll of all Vietnam veterans, including civilians, medical personnel, entertainers, and female veterans. The mortality rate for all male military personnel and individual service branches was compared with the mortality rate for the male Australian population. Not all deaths among Vietnam veterans could be identified within the databases used for the study. This resulted in an underestimation of the observed deaths and consequently an underestimation of the standardised mortality rate (SMR). Thus the results reported were adjusted for under-ascertainment based on the proportion of deaths found on the National Death Index and the Department of Veterans' Affairs client database.
Mortality was assessed from 1980 to 1994, as this was the period in which data from the National Death Index, which was begun in 1980, was available. The mortality rate for male veterans was significantly higher (SMR=1.07; 95% CI, 1.02-1.12) compared with the male Australian population of the same age. There was statistically significant increased mortality from all neoplasms, ischaemic heart disease, and suicide. The significant increase in neoplasms was attributed to elevated rates of prostate and lung cancers, cancers of the tongue, "other" digestive organs, and male breast, although the latter was due to only three cases.
Of the three service branches, Navy veterans had the highest overall mortality (SMR=1.37; 95% CI, 1.23-1.52) and the only significantly elevated overall mortality. The SMR for Army veterans was 1.00 (95% CI, 0.99-1.05) and for Air Force veterans 1.12 (95% CI, 0.97-1.27). The SMR for deaths from neoplasms among Navy personnel was 1.58 (95% CI, 1.31-1.89). Navy veterans also had significantly increased mortality due to diseases of the circulatory system (SMR=1.26; 95% CI, 1.04-1.52) and external causes (SMR=1.48; 95% CI, 1.15-1.86).
Mortality of National Service Vietnam Veterans study
A supplementary study to the Vietnam veteran mortality study was undertaken to examine mortality among National Service veterans and non-veterans. 7 This analysis eliminated the healthy worker effect inherent in comparing a military population with the general Australian population. It also extended the Australian Veteran Health Studies with an additional 13 years of death data. The total follow-up time was 22 to 29 years.
Mortality from all causes was significantly higher in National Service veterans (relative risk [RR]=1.15; 95% CI, 1.00-1.33). Death from all cancers was elevated, but not significantly. The lung cancer rate was twice that among non-veterans (RR=2.2; 95% CI, 1.1-4.3) and cirrhosis of the liver nearly triple (RR=2.7; 95% CI, 1.22-6.4). Brain cancer was also significantly elevated (RR=5.6; 95% CI, 1.53- >10), based on three cases.
As discussed above, the mortality for Army personnel was normal compared to the Australian male population. However, when a cohort of National Service Vietnam veterans (a subset of the Army personnel in the previous study) were compared with a cohort of National Service men who served in Australia, a statistically significant elevation in mortality was observed, although both groups had a lower mortality than the Australian male population. This suggests that a healthy worker effect could still be contributing to the mortality results.
Morbidity of Vietnam veterans studies
A series of studies assessing the morbidity of Vietnam veterans was begun in 1996. A self-completed health questionnaire was distributed to 49944 male veterans 8 and 278 female veterans. 9 More than 80% of the veterans contacted completed the survey. The questionnaire asked veterans to assess their own health, and provide details of their marital status, and the health of their partner and children.
The results of the survey were compared with expected community norms obtained from several surveys including the 1995 National Health Survey conducted by the Australian Bureau of Statistics. 10 The comparisons suggested that the health of Vietnam veterans and their families was worse than that of the Australian population. Even though the results were compared with the National Health Survey, there was no specific comparison group used for this questionnaire. As with all selfreported questionnaires, there may be mis-reporting due to misclassification of specific illnesses or respondents' unfamiliarity with medical terminology.
A series of validation studies were undertaken to assess the reported elevated rates of illness. The number of validated cases of melanoma and cancer of the prostate were significantly higher than expected. 11 There were 483 validated cases of melanoma compared with 380 expected cases according to community norms (95% CI, 342-418). For cancers of the prostate, 212 cases were validated and 147 expected (95% CI, 123-173). However significantly fewer lung cancers, soft tissue sarcomas, and cancers of the testis were observed than expected. For lung cancer, the authors noted that the fewer than expected cases was probably an artefact due to a number of veterans having died from lung cancer and consequently having been missed by the morbidity study. The number of confirmed cases of leukaemia was within the expected range, although the number of cases of chronic lymphatic leukaemia was at the upper limit of the confidence interval. Non-Hodgkin's lymphoma was elevated, with 66 validated cases, 48 expected (95% CI, 34-62). 12
The rare conditions of multiple sclerosis and motor neurone disease were validated among respondents to the morbidity questionnaire. 13 Based on clinical notes and death certificates, 20 cases of multiple sclerosis were validated among Vietnam veterans while 17 cases were expected, (95% CI, 9-26). Three cases of motor neurone disease were validated, compared with 1.2 expected, (95% CI, 0-3.3). This is the upper limit of significance for the expected number of cases of motor neurone disease. While the validation study was taking place one more validated case of motor neurone disease and two probable cases developed in Vietnam veterans who did not participate in the original morbidity survey.
Synopsis of results of the Australian studies
The Australian studies conducted since the mid 1990s have demonstrated a number of statistically significant increases in mortality and morbidity among Vietnam veterans. Specifically, overall mortality, mortality from neoplasms, circulatory diseases and external diseases are elevated when compared with the similarly aged male Australian population. In addition, the number of cases of motor neurone disease and chronic lymphatic leukaemia observed among Vietnam veterans suggests that significantly increased incidence may be revealed with continued follow-up. It should be noted that the Australian studies since 1996 have been government reports, and results have not been published in peer-reviewed journals. Nevertheless, independent scientific committees oversaw these studies.
Major American studies have investigated the effect of dioxin exposure among Ranch Hand Air Force personnel, the unit involved in spraying agent orange in Vietnam. To date, five health assessments of Ranch Hand Air Force personnel and a comparison group matched on age, race and military occupation have been undertaken (in 1982, 1985, 1987, 1992 and 1997). A sixth and final examination during 2002-2003 is scheduled to be reported in 2005. This study used serum dioxin measurements from 1987 to assess the level of exposure. In the latest report, 14 type 2 diabetes and cardiovascular abnormalities demonstrate the clearest positive association with dioxin exposure. In the 15 years of surveillance, the study has not shown any statistically significant association between dioxin exposure and malignant neoplastic disease among the Ranch Hand personnel.
For Vietnam veterans who were not in the Ranch Hand program, it has been difficult to reconstruct exposure to agent orange. However, in assessing the possible health effects of exposure to herbicides and pesticides experienced during Vietnam service, studies of occupational exposure of chemical and agricultural workers to dioxin and other herbicides or pesticides and studies of environmental contamination have been useful. For example, an accident in 1976 at a small Italian chemical plant exposed the local population to dioxin. This population has been extensively studied, which has contributed to the understanding of the human health effects of dioxin.
The Institute of Medicine publication Veterans and agent orange 15 provides researchers with an extensive review of information on the health effects of dioxin exposure and Vietnam service. This literature review, first published in 1994, is updated every two years and draws on veteran studies and studies of occupational and environmental exposure. The report categorises the association between specific health outcomes and exposure to herbicide into four groups: conditions with sufficient evidence of an association, conditions with limited/suggestive evidence, conditions with inadequate/insufficient evidence, and conditions with limited/suggestive evidence of no association. These categories are based on statistical association reported in the literature, not on causality. The strength of the reported association is assessed on the quality of the study and the extent to which chance, bias, and confounding were addressed.
In the latest update of Veterans and agent orange, 16 five diseases were classified as having sufficient evidence of an association with herbicide exposure. These diseases are: chronic lymphocytic leukaemia, soft-tissue sarcoma, non-Hodgkin's lymphoma, Hodgkin's disease, and chloracne. An additional seven diseases have limited or suggestive evidence of an association between herbicides and outcome. That is, there is at least one high quality study that shows a positive association, but the results of other studies are limited and inconsistent. The seven conditions are: respiratory cancer, prostatic cancer, multiple myeloma, acute and subacute transient peripheral neuropathy, porphyria cutanea tarda, type 2 diabetes and, in children of veterans, spina bifida maxima.
The difficulty for epidemiological studies of Vietnam veterans has been the inability of researchers to accurately quantify and separate the exposure associations of herbicides and other wartime hazards with long-term health outcomes. Australian studies have generally assessed exposure as Vietnam service and refined this only to the level of Service branch, corps grouping, and time in Vietnam.
A recent Australian report by the National Research Centre for Environmental Toxicology has identified a potential exposure of Navy personnel to dioxins through potable water produced by evaporative distillation. 17 By constructing a model of the evaporative distillation system used on HMAS Sydney, this study has shown that, in the process of evaporative distillation of potable water, organochlorine pesticides and dioxins, if they had been present in the source sea or estuarine water, would have codistilled and been concentrated. Possible exposure to dioxin for Navy members through the ingestion and personal use of the potable water was estimated to have been several orders of magnitude above what are acceptable standards today.
Exposure assessments in US studies have relied on the US Department of Defense HERBS file. This is a comprehensive file of the Air Force Ranch Hand herbicide spray missions. However, the file did not contain sufficiently coherent data to formulate an exposure reconstruction.
Recent advances by the Columbia University group led by Stellman have greatly increased the potential for researchers to make more accurate assessments of exposure to herbicides for specific military units deployed during the Vietnam conflict. 18 The group has developed a geographic information system that characterises exposure to herbicides in Vietnam. The system has combined several databases, some only recently discovered in US Defense archives, which incorporate flight paths of aerial spray missions, the amount and type of agents sprayed, identification and location of military units and troops, land features, soil typology, and location of civilian populations to produce an exposure opportunity index (EOI). The EOI is based on the proximity in time and space to spraying. It does not measure dose, but provides a systematic method for assessing potential exposure. A user-friendly system is being developed which will allow researchers to input dates and locations of units or troops and receive a Microsoft Excel format output of EOIs.
Conclusion and future directions
The numerous studies on Vietnam veterans over more than thirty years since the war have shown substantial physical health effects as a result of service during the Vietnam conflict. Elucidating the differential impact of the multitude of factors that may be associated with poor health outcomes for Vietnam veterans presents unique challenges for researchers. Nevertheless, research into the health of Vietnam veterans continues. The Australian Department of Veterans' Affairs is currently conducting the Third Vietnam Veteran Mortality Study and Cancer Incidence in Vietnam Veterans Study. 19 This study will undertake a ship-by-ship analysis for Navy and Army small ships and will be the first time a cancer incidence study has been undertaken on Navy and Air Force Vietnam veterans.
Development of spatial epidemiological tools may substantially advance the understanding of the effects of environmental and occupational hazards on the long-term health of deployed troops. This new methodology has the potential to be applied retrospectively for Australian Vietnam veterans or prospectively for current deployments. Indeed, the United States has recognised the potential of this valuable methodology in the Iraq War where they have recorded the real time location of all personnel with a geographic information system in conjunction with surveillance of environmental health conditions. 20 In any future health study of Iraqi War veterans it may be possible for researchers to assess the association between exposures and health outcomes with more certainty than was previously achievable.
The authors have no conflict of interests to declare.
Dr Eileen Wilson received a Masters of Science in Microbiology from Harvard University School of Public Health and completed her PhD at the National Centre for Epidemiology and Population Health, The Australian National University. She is currently involved in the Third Vietnam Veterans Mortality Study, Cancer Incidence in Vietnam Veterans Study and studies of Korean War veterans.
Dr Keith Horsley has worked in the Department of Veterans' Affairs in a variety of roles. In his most recent position, he has been involved in research in Vietnam veterans, Korean War veterans, Gulf War veterans, Nuclear Test Participants and personnel involved in the F-111 aircraft.
Department of Veterans' Affairs, Woden, ACT.
Eileen J Wilson, MSc, PhD, Epidemiologist;
Keith WA Horsley, MBBS, MPubAdmin, Director of Research Studies.
Correspondence: Dr Eileen J Wilson, Department of Veterans' Affairs, PO Box 21, Woden, ACT 2606. email@example.com