Vietnam veterans who served from 1962-1971 have double the rate of chronic lymphatic leukemia compared to the general population according to a new study by the University of Otago’s Department of Preventive and Social Medicine.
Nearly 3400 New Zealand military personnel served in Vietnam and the study examined the health records of 2752 men from 1988 to 2008. This is the first cohort study of New Zealand Vietnam veterans which assesses long-term health effects of serving in a combat zone.
The study says most veterans deployed in the Nui Dat area of Phuoc Tuy province, experienced a ‘toxic environment’ because of the widespread use of 2,4,5-T and 2,4-D as defoliant herbicides.
This mixture is more commonly known as Agent Orange and was contaminated with the carcinogen 2,3,7,8,TCDD, or ‘dioxin’. However the study does not have specific data on herbicide exposure of individual soldiers.
The US Institute of Medicine, in their report ‘Veterans and Agent Orange: Health Effects of Herbicides Used in Vietnam’ first classified chronic lymphatic leukemia on their ‘sufficient evidence for cancer’ list in 2002, based on dioxin toxicity and studies of farm workers exposed to herbicides. The cohorts of Australian and New Zealand soldiers are the only group of Vietnam veterans to show an actual excess of the disease.
The results also show that although 407 veterans died over the study period the overall rate of death from all causes was 15% lower than the general population suggesting lower incidence of mortality and morbidity. Mortality from cancer was not significantly lower or higher however than the general population, and there was no decrease in ‘all cancer’ incidence.
“The pattern of lower overall mortality is known as the ‘healthy soldier effect’ which is related to the fact that this cohort would have been selected for its health and fitness,” says lead author Dr David McBride.
“However the study shows a doubling of the risk of mortality from cancers of the head and neck, as well as an increase in oral cancers of the pharynx and larynx. Lung cancer contributed the greatest burden of deaths in both New Zealand and Australian veterans.”
Dr McBride and colleagues say the findings are not at odds with evidence needed for compensation from Veterans Affairs New Zealand for ill-health caused by service in the Vietnam War.
The researchers say that further work is still needed, including the selection of a non-deployed comparison group to reduce the ‘healthy soldier effect.’ As some of the cancers are also associated with smoking and alcohol consumption there is a need to collect further information on confounding factors such as ethnicity, smoking and alcohol use.
The current study will shortly appear in the international journal BMJ Open and was funded by the War Pensions Medical Research Trust Fund. A copy of the paper is available on request to Dr McBride.
The University of Otago Research Theme ‘Health of Veterans, Serving Personnel and their Families’ is holding its annual two-day colloquium on Tuesday the 3rd and Wednesday the 4th of September, hosted by the Dunedin Club.