IoM Study Finds Agent Orange-Diabetes Link - Matt Pueschel
WASHINGTON Vietnam war veterans who suffer from adult-onset diabetes soon will receive benefits and compensation for their illness thanks to a new study by the Institute of Medicine about the effects of the herbicide agent orange.
According to a report released in October, an IoM committee of 13 outside experts found that there is "limited or suggestive" evidence of an association between exposure to the herbicides used in Vietnam or the contaminant dioxin and Type 2 diabetes. The finding represents a change in classification from previous IoM reports on agent orange and diabetic veterans, which revealed inadequate/insufficient evidence to determine whether an association existed.
In response, acting VA secretary Hershel W. Gober announced last month that Type 2 diabetes will be added to the list of presumptive diseases associated with herbicide exposure in Vietnam. Eligibility for disability compensation for those who have the disease will apply to honorably discharged veterans who served in Vietnam between Jan. 9, 1962, and May 7, 1975.
While the limited/suggestive designation doesn't conclusively say that agent orange causes diabetes, the same designation has been used in the past to allow veterans to receive compensation from the VA for other service-connected conditions presumably caused by agent orange.
Prior to Gober's decision to include Type 2 diabetes on the list for presumed service connections for Vietnam veterans, Rep. Lane Evans (D., Ill.), minority leader of the House Veterans Affairs Committee, had introduced a bill (HR 5438) designed to accomplish the same thing and urged Gober to issue the regulation so that the legislation wouldn't be necessary.
Although Gober decided to issue the regulation, VA officials have cautioned that it will take several months to write the rules before Vietnam veterans with Type 2 diabetes can begin applying for disability compensation. VA has 60 days to publish proposed rules for implementing the new regulation's effect on benefits. After the rules are published, a 90-day period will ensue to allow VA time to seek input and public comment on the proposal. VA will then publish final implementation rules.
The policy will expand an already growing list of diseases VA has recognized as being associated with agent orange that are now considered to be service-connected: chloracne, porphyria cutanea tarda, acute or subacute peripheral neuropathy, non-Hodgkin's lymphoma, soft tissue sarcoma, Hodgkin's disease, multiple myeloma, prostate cancer, respiratory cancers and Vietnam veterans? children born with spina bifida.
"At the moment, everything in the ?sufficient? or ?limited/suggestive? [categories], VA has chosen to treat as service-connected," said David Butler, PhD, IoM's study director on the agent orange project. "That wasn't always the case. They've done it since ?97."
Bill Crandell, minority staff director for the House Veterans Affairs subcommittee on oversight and investigations, said IoM has used the limited/suggestive rating consistently in its reports on agent orange for the past several years. He said an initial list of illnesses with "solid" ties to agent orange was produced, followed by others that showed limited/suggestive ties. "It could be a 30 to 60 per cent probability," he said "Basically, this [designation] increases the risk. It also has the tendency to bring on conditions earlier than the rest of the population."
The IoM Study
The diabetes report is part of a series of studies performed by IoM for the VA under the "Agent Orange Act of 1991," which directed the VA secretary to ask the National Academy of Sciences (NAS) to conduct comprehensive reviews and evaluations of medical information regarding agent orange, other herbicides used in Vietnam and their various chemical components.Dr. Butler said the act called for a 1994 report on the relationship between the herbicides and veterans and subsequent reports every two years after that for 10 years. VA funds the studies, but IoM maintains its independence in its analyses and conclusions.
"The common thread was that Congress instructed VA to ask IoM to do comprehensive literature reviews on the science regarding herbicides used in Vietnam and their contaminants, primarily dioxin, and their health effects," said Dr. Butler.
The committee's most recent conclusions on the diabetes-agent orange link were based on cumulative evidence from scientific literature reviewed in its previous studies and relevant papers published in the last two years. "There is not a lot written on VA or Vietnam veterans," said Dr. Butler. "There is the Ranch Hand [Air Force] study, but most are from populations exposed to industrial settings, such as herbicide manufacturers, and populations exposed as a result of accidents in the past."
Although the committee found that no single paper or study led to its new conclusion, it found that the information on diabetes over years of research now meets the definition established for limited/suggestive evidence ' which is defined in the report as "suggestive of an association between herbicides and the outcome, but limited because chance, bias, and confounding could not be ruled out with confidence"' and that studies could not have isolated all of the variables that could have affected the outcome.
"There wasn't any one report that swayed this one way or another," said Dr. Butler. "While you wouldn't take one of them and say ?Whoa, here's the smoking gun,? when a bunch of things go in the same direction, you might say here's an effect. You can see differences popping up between the general population and the population that's had significant exposure [to dioxin]."
Dr. Butler said that when taken altogether, particularly the new morbidity and mortality studies published over the last several years, the committee reached a consensus that there was a trend that was suggestive of an association between diabetes and agent orange.
According to a statement from IoM (which is part of the National Academy of Sciences), there is a plausible link between dioxin exposure and biologic changes associated with diabetes. Dr. Butler said dioxin was a contaminant of the chemical 24D and a hyperchlorinated particle of 245T (agent orange was a 50/50 mixture of these two chemicals).
"It must be emphasized, however, that any increased danger from herbicide or dioxin exposure appears to be small," said IoM's committee chairman on the project David J. Tollerud, MD, MPH, public health professor and director of the Center for Environmental and Occupational Health at MCP Hahnemann University School of Public Health in Philadelphia. "The known predictors of diabetes risk family history, physical inactivity and obesity continue to greatly outweigh any suggested increased risk from wartime exposure to herbicides."
Cumulative Evidence
Four mortality studies were reviewed by the IoM committee in compiling its latest report on agent orange. A study of individuals living near the site of a 1976 industrial accident that involved dioxin in Seveso, Italy, found that they had a higher risk of diabetes death than a reference population in all exposure zones. Dr. Butler said a latency period of 15-20 years is commonly used when studying the effects of the disease.Several studies on Type 2 diabetes morbidity were also reviewed by the committee, including a survey of Vietnam veterans from Australia, a National Institute for Occupational Safety and Health (NIOSH) study of U.S. chemical workers and an update on the Air Force Health Study (Ranch Hand). The survey of male Australian veterans of Vietnam revealed 2,391 cases of self-reported diabetes when only 1,780 were expected. Another survey of female Australian veterans of Vietnam showed only 5 self-reported cases when 10 were expected, but the NIOSH and Ranch Hand studies both showed an elevated incidence of diabetes in individuals who had high levels of serum dioxin relative to others examined.
Although the Air Force study showed nearly identical diabetes incidence in Ranch Hand veterans and the matched comparison group, dose-response relationships between dioxin levels and diabetes incidence were observed in several analyses. Furthermore, animal, laboratory and human data continue to provide reasonable evidence that TCDD (Tetrachlorodibenzo-p-dioxin) exposure could affect Type 2 diabetes risk in humans.
When asked whether a single high dose exposure to dioxin, such as what occurred at Seveso, or a sustained occupational exposure places an individual more at risk to acquire diabetes, Dr. Butler said it's not "immediately clear" which is more important. "You see both happening," he said, adding that the next IoM report on agent orange will focus on 30 to 35 medical conditions, including diabetes.
TCDD, or dioxin, was an unintentional contaminant of one of the four herbicides used in Vietnam. Beginning in 1962, U.S. forces sprayed millions of gallons of agent orange and other defoliants over parts of South Vietnam to destroy jungle hiding places and enemy crops. According to IoM, a 1969 scientific report concluded that one of the primary chemicals used in agent orange could cause birth defects in laboratory animals. The military suspended the use of agent orange in 1970 and halted all herbicide spraying in Vietnam in 1971.
Diabetes Testing Urged
Since the new IoM report was released, leaders of the House Veterans Affairs Committee have called on Vietnam veterans to seek a routine health care examination for Type 2 diabetes. "The VA's decision to compensate veterans who served in Vietnam and who later develop diabetes is a generous one," said committee chairman Rep. Bob Stump (R., Ariz.) in a statement. "Any veteran who served in Vietnam and who has not seen a doctor in the last several years should strongly consider calling the VA and requesting a physical examination. The VA can provide an examination at no expense. If diabetes is diagnosed and treated, serious health complications can be avoided."According to the Centers for Disease Control and Prevention, nearly 16 million Americans have diabetes and about a third aren't aware of their condition. The prevalence among VA patients is substantially higher, holding at about 16 per cent. Type 2 diabetes accounts for 90 to 95 per cent of diabetes cases. With proper treatment and lifestyle changes, according to the VA, complications such as blindness, amputations, heart disease, kidney failure and premature death can be prevented or delayed.