Department of Epidemiology and Preventive Medicine, Monash University, Melbourne
Department of Epidemiology and Preventive Medicine, Monash University, Melbourne
Australian Centre for Post-traumatic Mental Health, University of Melbourne, Melbourne
Department of Epidemiology and Preventive Medicine, Monash University, Melbourne
Department of Psychiatry, University of Adelaide, Adelaide
Department of Epidemiology and Preventive Medicine, Monash University, Melbourne
Menzies Centre for Population Health Research, University of Tasmania, Hobart
Royal Australian Navy, retired, Canberra
Australian Government - Department of Veterans'Affairs, Canberra
Health Services Australia, Melbourne, Victoria, Australia
Correspondence: Jillian Ikin, Monash University, Department of Epidemiology and Preventive Medicine, Central and Eastern Clinical School, Alfred Hospital, Commercial Road, Melbourne, VIC 3004, Australia. Tel: +61 3 9903 0555; Fax: +61 3 9903 0556; e-mail: jill.ikin{at}med.monash.edu.au
Declaration of interest Supported by the Australian Government - Department of Veterans'Affairs.
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ABSTRACT |
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Aims To measure psychological disorders in Australian Gulf War veterans and a military comparison group and to explore any association with exposure to Gulf War-related psychological stressors.
Method Prevalences of DSM-IV psychological disorders were measured using the Composite International Diagnostic Interview. Gulf War-related psychological stressors were measured using a service experience questionnaire.
Results A total of 31% of male Gulf War veterans and 21% of the comparison group met criteria for a DSM-IV disorder first present in the post-Gulf War period. The veterans were at greater risk of developing post-Gulf War anxiety disorders including post-traumatic stress disorder, affective disorders and substance use disorders. The prevalence of such disorders remained elevated a decade after deployment. The findings can be explained partly as a war-deployment effect. There was a strong dose-response relationship between psychological disorders and number of reported Gulf War-related psychological stressors.
Conclusions Service in the 1991 Gulf War is associated with increased risk of psychological disorders and these are related to stressful experiences.
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INTRODUCTION |
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We report the results of psychological health assessments in a cross-sectional study of the entire cohort of Australian veterans of the 1991 Gulf War and a randomly sampled military comparison group who did not deploy to that conflict. The aim of this investigation was to use a validated, diagnostic interview, utilising the criteria of DSM-IV (American Psychiatric Association, 1994), to determine whether Australian Gulf War veterans have been at increased risk of developing psychological disorders at any time since the Gulf War or at increased risk of having a psychological disorder in the past 12 months. The study explored whether any excess risk of psychological disorders could be explained as a war deployment effect. Furthermore, a military experience questionnaire was used to investigate any association with psychological stressors experienced during the Gulf War deployment. Finally, a prediction model was applied to investigate the possible effects of participation bias.
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METHOD |
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Recruitment
The study population was the entire cohort of 1871 Australian veterans who
served in the Gulf region during the period 2 August 1990 to 4 September 1991.
They included 1579 members of the Royal Australian Navy, 123 members of the
Australian Army and 169 members of the Royal Australian Air Force. The
Australian Gulf War deployment included 38 women.
The comparison group of 2924 individuals was selected randomly from 26 411 Australian Defence Force personnel who were in operational units at the time of the Gulf War and therefore were fit to deploy but did not deploy to that conflict. The comparison group was frequency matched to the Gulf War veteran group by service type, gender and 3-year age bands. The comparison group sample included 74 women.
Participants were recruited via mailed invitation with two further mailings and intensive follow-up telephone contact for non-responders. Last known addresses were obtained from several databases maintained by the Department of Veterans' Affairs and by the Department of Defence.
Data collection
Participation in the study included completing a postal questionnaire and
undergoing a comprehensive health assessment. The health assessments were
carried out by trained teams comprising a doctor, nurse and psychologist at
ten Health Services Australia medical clinics located around Australia. Some
individuals were unable or unwilling to attend the health assessment but
completed the postal questionnaire.
Interviewer-administered psychological health assessment
Individuals who attended the health assessment at Health Services Australia
medical clinics were evaluated for any history of affective, anxiety, somatic
and substance use disorders according to diagnostic criteria described in the
DSM-IV, using the interviewer-administered and computer-assisted version of
the Composite International Diagnostic Interview (CIDI): the CIDI-Auto 2.1
(World Health Organization,
1997). The CIDI is a structured interview of demonstrated
reliability and validity for research purposes
(Farmer et al, 1987;
Wittchen et al, 1991;
Janca et al, 1992).
The instrument has been used widely, including in the 1997 Australian National
Survey of Mental Health and Well-being
(Australian Bureau of Statistics,
1998) and in the 1990 and 2001-2002 US National Comorbidity
Surveys (Kessler et al,
1994,
2003). All interviews were
carried out face to face by registered psychologists who were specifically
trained in the administration of the CIDI. The psychologists were initially
masked to each individual's study group, and participants were asked to
refrain from revealing this information during the course of the interview if
possible. However, study group may have been surmised by the psychologists on
the basis of certain responses during the interview. Using standard output
from the CIDI, individuals were classified according to any diagnosis of the
following:
Postal questionnaire
The postal questionnaire enquired about demographic variables, including
age, gender, country of birth, educational level, marital status, occupational
status, service type and rank at the time of the Gulf War. Participation in
active deployments other than the Gulf War was also reported. Active
deployments were defined as war or peacekeeping deployments and specifically
excluded training exercises or goodwill visits.
Exposure to psychological stressors during the Gulf War was measured using the Military Service Experience questionnaire, which was developed specifically for this study of Australian military personnel. The questionnaire comprised 44 items, each representing a potentially stressful experience considered relevant to Australian Defence Force military service, including the Gulf War. The items were largely based on information drawn from a focus group of Australian Gulf War veterans. Some items were modified from pre-existing combat exposure questionnaires, such as the Laufer Combat Scale (Gallops et al, 1981) modified for studies of US Gulf War veterans (Erickson et al, 2001), the Combat Exposure Scale (Keane et al, 1989) and the Operation Desert Storm Exposure Scale (Wolfe et al, 1993; Sutker et al, 1995). Common themes covered by the Military Service Experience questionnaire items included fear of entrapment below the waterline on ships, fear of death, threat of biological or chemical attack, exposure to the death or suffering of others, feelings of helplessness and lack of control, poor preparation, malevolent environment, lack of support and lack of unit cohesion. Respondents indicated whether or not they had experienced individual items during the Gulf War. The questionnaire was scored by summing the number of positive responses, providing a score range of 0-44.
Statistical analysis
Owing to very small numbers of female Gulf War veterans, the analyses were
limited to males. Statistical analyses were performed using Stata
(StataCorp, 2001). Differences
between the Gulf War and comparison group participants on demographic
variables were assessed using chi-squared tests for categorical measures and
t-tests for continuous measures. Associations between Gulf War
deployment and psychological disorders, after adjusting for potentially
confounding factors, were assessed using logistic regression and reported as
adjusted odds ratios with 95% confidence intervals. Odds ratios for
CIDI-defined post-Gulf War disorders are incident odds ratios, and odds ratios
for CIDI-defined disorders present within the previous 12 months are
prevalence odds ratios. Where fewer than five people in either study group
experienced the disorder of interest, exact logistic regression was performed
(CYTEL Software Corporation,
2000). Likelihood ratio tests
(Hosmer & Lemeshow, 2000)
were performed to investigate homogeneity of the effects of study group across
categories of age, rank and service type. These were performed using
interaction terms added to the logistic regression model. To explore the
relationship between CIDI disorders and Gulf Warrelated psychological
stressors in Gulf War veterans, exposure-response trends were computed using
the Military Service Experience questionnaire score as a linear variable in
the regressions.
Assessment for participation bias
Typically, in Gulf War veteran research the participation rates in the
non-Gulf comparison groups have been low
(Goss Gilroy, 1998; Ishoy et al, 1999;
Unwin et al, 1999;
Kang et al, 2000,
2003), rendering the results
of these studies vulnerable to participation bias. To investigate possible
participation bias in this study, we collected some brief demographic and
Short Form 12 (SF-12) Health Survey (Ware et al,
1996,
1998) data on a number of
non-participants via a telephone-administered questionnaire. Study
participants who completed the postal questionnaire also completed the SF-12
in that instrument.
A complete description of the analysis conducted to assess participation bias in this study can be obtained from the authors. To summarise, a prediction model was used to impute SF-12 scores for all non-participants by using the relationship observed between SF-12 scores and study group, age, rank, service type and serving status in those non-participants who completed the telephone questionnaire. Subsequently, by using the relationship observed between the SF-12 scores of participants, the above demographic variables and their CIDI-defined psychological health outcomes, it was possible to impute CIDI results for all non-participants. This procedure, replicated 100 times, was applied to each of the major post-Gulf War psychological health outcomes, each time computing an age-, rank- and service-adjusted odds ratio for the relative health of Gulf War veterans v. those in the comparison group as if the study had achieved full participation. The difference between the average imputed odds ratios and the actual observed odds ratios among participants represented the degree of participation bias.
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RESULTS |
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The total eligible sample in the comparison group was 2796 after removal of those reported deceased (n=31) or overseas (n=97). The overall participation rate in the comparison group was 56.8% with 1588 participants. These included 1411 (50.5%) who completed both the health assessment and postal questionnaire and a further 177 (6.3%) who completed the postal questionnaire alone. The 1588 comparison group participants included 1548 men (97.5%), of whom 1377 (89.0%) completed the psychological health interview.
Demographics
Demographics are shown in Table
1 for all male participants. Gulf War veteran participants were
slightly younger than comparison group participants, more likely to have
served in the Navy, less highly ranked and less likely to have tertiary
education. There were no differences in other variables. Just under 60% of
participants in each group were no longer serving members of the Australian
Defence Force at the time of recruitment.
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Participation in active deployments other than the Gulf War
In addition to their deployment to the Gulf War, 44% of male Gulf War
veterans (n=625) reported participation in at least one other active
deployment. One-third of the male comparison group (n=514, 33%)
reported participation in at least one active deployment.
CIDI-defined DSM-IV psychological disorders
The results for CIDI-defined pre-Gulf War disorders and CIDI-defined
post-Gulf War disorders in males are shown in
Table 2. Prevalences of most
pre-Gulf War disorders were similar in the two groups, indicating that they
varied little in their overall levels of psychological morbidity prior to the
time of the Gulf War deployment.
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Gulf War veterans (31%) were more likely than the comparison group (21%) to develop post-Gulf War psychological disorders. The greatest increased risks were for anxiety disorders, including PTSD, obsessive-compulsive disorder and social phobia. There were also increased risks for post-Gulf War bipolar disorder, major depression, alcohol dependence or abuse and drug dependence or abuse. The levels of post-Gulf War somatic disorders were very low in both groups and no participants were found to have somatisation disorder.
Table 3 shows CIDI-defined disorders present within the previous 12 months. The highest odds ratios were for anxiety disorders, including PTSD, obsessive-compulsive disorder, social phobia, panic disorder and agoraphobia, which were three to five times more likely in Gulf War veterans. Excesses also were found for bipolar disorder, major depression and alcohol dependence or abuse. On average, Gulf War veterans had twice as many disorders present in the previous 12 months as the comparison group.
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Investigation of a deployment effect
Approximately two-thirds of the comparison group had never been on active
deployment and therefore it was possible that the excess risk of psychological
disorders in Gulf War veterans could be explained as a war deployment
effect rather than an effect more specific to the Gulf War. To
investigate this we repeated the analysis of
Table 3, but using only those
in the comparison group who reported at least one active deployment and who
completed the CIDI. The results are shown in
Table 4 for the major
categories of CIDI-defined disorders present within the previous 12 months.
The adjusted odds ratio for PTSD was reduced from 4.2 to 2.1, with the
remaining odds ratios the same or slightly lower than those presented in
Table 3 where all comparison
group participants were included. The average number of active deployments
reported by each of the two groups was similar and additional analysis (data
not shown), adjusting for number of active deployments, made little difference
to the adjusted odds ratios in Table
4.
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Risk across age, service type and rank
We investigated the effects of study group across subgroups of age, service
type and rank upon four major categories of CIDI-defined post-Gulf War
disorder: any affective disorder, any anxiety
disorder, post-traumatic stress disorder and any
substance disorder. Within almost every subgroup of age, service type
and rank, Gulf War veterans were more likely to develop CIDI-defined post-Gulf
War disorders than the comparison group. Tests for interaction indicated that
there was no statistically significant variation in the adjusted odds ratios
across the subgroups of age, service type and rank, showing that the Gulf War
deployment did not differentially increase risk in any one subgroup. These
findings are illustrated in Table
5 for any anxiety disorder. The pattern of results
for tests of interaction were similar in the other major categories of
post-Gulf War CIDI disorder.
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Effect of Gulf War-related psychological stressors
For Gulf War veterans only, Table
6 presents the effects of Gulf War service-related Military
Service Experience questionnaire scores upon CIDI-defined post-Gulf War
psychological disorders. Exposure to increasing numbers of Gulf War-related
stressors was strongly associated with increasing risk for all psychological
disorders. The dose-response slopes indicated that the predicted increase in
the odds of each disorder, per unit increase in Military Service Experience
score, varied from 10% for any substance use disorder to 23% for PTSD.
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Investigation for participation bias
The telephone questionnaire for non-participants, upon which part of the
participation bias prediction model was based, was completed by approximately
22% (n=77) and 28% (n=334) of all Gulf War veteran and
comparison group non-participants, respectively. The average and range of the
100 imputed odds ratios, representing the best estimate of the true difference
in risk of CIDI-defined post-Gulf War psychological disorders between Gulf War
veterans and those in the comparison group as if full participation in the
study had been achieved, are shown in the right section of
Table 7. These full
participation odds ratios are fractionally lower but within 5% of those
observed for actual participants. If participation bias exists, it appears to
be slight and possibly leads to a very minor overestimation of risk.
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DISCUSSION |
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Because similar illnesses have affected veterans of past wars (Hyams et al, 1996), causality may be linked to a common war experience rather than to a specific aspect of the 1991 Gulf War. The Gulf War effect could be a war deployment effect whereby military personnel who deploy to any war-like environment develop poorer health than military personnel who have not been actively deployed. This theory is partly refuted by the findings of a British study in which UK Gulf War veterans reported symptoms and disorders significantly more frequently than UK veterans of the Bosnia conflict (Unwin et al, 1999), suggesting that exposures or experiences more specific to the Gulf War are responsible. No specific characteristics of Gulf War service, however, have been associated consistently with the increased risk of psychological disorders. The UK studies report associations between psychological ill health and lowest rank (Ismail et al, 2000) and some Gulf War-related experiences, including injury, seeing maimed soldiers and dismembered bodies, dealing with prisoners of war and the sounding of chemical alarms (Unwin et al, 1999). Psychological ill health in US Gulf War veterans has been associated with brief measures of war zone stress (Sutker et al, 1995; Kang et al, 2003). The US volunteer registry studies also report associations with younger age (Joseph et al, 1997) and reservist status (Persian Gulf Veterans Coordinating Board, 1995) but no other demographic, exposure or geographical risk factors. Data collection in relation to psychological stressors in these Gulf War studies typically has been limited to only a few variables.
Overview of results
Our study clearly demonstrates increased risk of the development of anxiety
disorders, including PTSD, affective disorders and substance- and alcohol-use
disorders, in Australian male veterans of the 1991 Gulf War compared with
Australian Defence Force personnel who were in operational units at the time
of the Gulf War but who did not deploy to that conflict. The increase in risk
of psychological disorders has occurred since the time of the Gulf War, with
the two groups demonstrating similar psychological health patterns prior to
the war. Although the majority of Gulf War veterans did not develop any
psychological disorder in the period since the Gulf War, our findings, using a
psychologist-administered, validated diagnostic interview and DSM-IV criteria,
provide more robust evidence of increased psychological ill health in Gulf War
veterans than that presented in previous studies employing primarily
self-reported symptom-based measures only
(Iowa Persian Gulf Study Group,
1997; Goss Gilroy,
1998; Ishoy et al,
1999; Unwin et al,
1999; Kang et al,
2003). The excess risk of psychological disorders in Gulf War
veterans can be explained only partly as a generalised war deployment
effect. In addition, our results show a strong dose-response
relationship between post-Gulf War psychological disorders and increasing
numbers of psychological stressors experienced during the Gulf War.
Measurement of psychological disorders
The use of the CIDI provided a valuable opportunity to investigate, and
control for, the presence of psychological disorders prior to the time of the
Gulf War. This has not been done in previous studies. The results indicated
that the prevalence of pre-Gulf War psychological disorders was similar in the
two groups. Since the time of the Gulf War, however, a higher proportion of
Australian male Gulf War veterans than comparison group members have developed
psychological disorders. In addition, at the time of the study and more than a
decade after the Gulf War, Australian Gulf War veterans were more likely to
show evidence of psychological disorders present within the previous 12
months. Gulf War veterans have been at greatest risk of developing anxiety
disorders, including PTSD where the elevation in risk is approximately
fourfold.
Investigation for a war deployment effect
The lack of differences between the two groups in pre-Gulf War
psychological morbidity and the heightened emergence of new disorders in the
Gulf War veteran group since the time of the Gulf War provide evidence to
suggest that the cause lies in the exposures and experiences of the Gulf War
deployment. This Gulf War effect, however, could be explained
partly as a common war deployment effect, whereby deployment to
any major war-like environment is expected to result in poor psychological
health. This is supported partly by the finding that the excess risk of PTSD
in Gulf War veterans is reduced when Gulf War veterans are compared with just
those comparison group subjects who have been on active deployments. Full
investigation for a war deployment effect is limited, however,
by the fact that the number of comparison group members reporting active
deployments is relatively small and the destinations and natures of these
deployments are many and varied. Most of these deployments, for example,
involved small groups on peace-keeping missions.
Association with Gulf War-related stressors
We found the risk of developing psychological disorders in Australian Gulf
War veterans to be associated strongly with increasing numbers of
psychological stressors experienced during the Gulf War, as measured using the
Military Service Experience questionnaire. Few previous Gulf War studies have
included measures of war-related stress, and those that did
(Sutker et al, 1995;
Kang et al, 2003)
based their measurements on a limited range of stressful factors. Kang et
al (2003) associated
their symptom-based measure of PTSD with a measure of Gulf War stress severity
derived from service type, deployment status and responses to three exposure
items. Sutker et al
(1995) found an association
between psychological distress and increasing scores on a brief war zone
severity scale. Development of the Military Service Experience questionnaire
allowed us to assess veterans' exposure to a wide range of stressful Gulf
War-related experiences. It should be noted that the Australian Gulf War
deployment involved few direct military attacks and resulted in no deaths and
few casualties. Consequently, instead of reporting stressors of a direct
combat nature, Australian veterans commonly reported stressors in relation to
the threat of combat, fear associated with its uncertainty (particularly the
risk of chemical or biological agent attack) and the isolation and discomfort
of deployment.
The number of these stressors identified by veterans was strongly predictive of psychological ill health in this war-exposed group. The relationship between traumatic or stressful exposure and subsequent psychopathology needs, however, to be interpreted cautiously. The Military Service Experience questionnaire was newly developed for this study and its psychometric properties have not been explored thoroughly. Further, several studies have questioned the stability of recall of military exposures over time. Some prospective studies of Gulf War veterans (Southwick et al, 1997) and veterans of the 1994 conflict in Somalia (Roemer et al, 1998) have demonstrated that as PTSD symptoms increase, for example, so does amplification of memory for traumatic or stressful events. Wessely et al (2003) found a similar association between worsening perception of health (though not worsening psychological health) and increased reporting of Gulf War exposures. In this longitudinal study the authors suggest that considerable media attention, given to the Gulf War and its health effects over the specific interval of the study, could help explain the observed changes in reporting. These various findings raise questions about the validity of any retrospectively determined relationship between the level of exposure to trauma and the degree of psychological symptoms subsequently manifested. Recall bias could explain at least some of the association observed in our study between the reporting of Gulf War-related experiences of threat or fear and psychological disorders.
Association with age, service type or rank
The increased risk of post-Gulf War psychological disorders associated with
deployment to the Gulf War did not vary significantly across subgroups of age,
service type and rank. These findings suggest that, compared with the
comparison group, there is unlikely to be some unique combination of exposures
or experiences particular to Gulf War veterans of different age, service type
or rank groups that is associated with the elevation in psychological
disorders in this veteran group. The finding in relation to service type is
limited by the vast predominance of one service type (navy) in our sample. Our
finding in relation to rank may be limited also by the predominance of navy
personnel in the Australian deployment; within the confines of ships it is
possible that there is only limited variation in the exposures and experiences
of naval personnel across different ranks.
Investigation for participation bias
The participation rate in our non-Gulf War comparison group was moderately
low, although comparable to other Gulf War veteran studies involving non-Gulf
War comparison groups and data collection via questionnaire alone
(Goss Gilroy, 1998;
Holmes et al, 1998;
Unwin et al, 1999;
Kang et al, 2000,
2003) or questionnaire and
medical examination (Ishoy et al,
1999). Despite an immense effort to contact and motivate the
comparison group, difficulties in recruitment reflect the highly mobile nature
of this relatively young adult population, the high turnover within the
defence forces (with close to 60% of both study groups no longer serving with
the Australian Defence Force) and the apparent lack of incentive for non-Gulf
War comparison group members to participate in Gulf War veteran health
research. The differential participation rates contributed to some differences
in the demographic profile of the two study groups and rendered the results of
the study vulnerable to the effects of participation bias and confounding. Our
investigation of the possible effects of participation bias, however, suggest
that our study results may be robust despite some non-participation in the
comparison group, and that participation bias is unlikely to explain the
excess risks found in Gulf War veterans in our study. The participation bias
analysis and its underlying assumptions, however, must be treated with some
caution. The telephone survey, for example, upon which part of the prediction
model was based, was completed by approximately a quarter of all study
non-participants and the model assumed that the telephone respondents' answers
were representative of those of the remainder of the non-participants.
Statistical adjustment for the possible confounding effects of demographic
variables, including age, rank, service type, education and marital status,
indicated that differences in these variables were unlikely to explain the
excess risk.
Implications
The fact that the prevalences of psychological disorders are notably
elevated in Gulf War veterans more than a decade following the Gulf War
suggests a high level of chronicity and possibly poor prognosis. Comorbidity
with PTSD, for example, is very common
(Creamer et al, 2001)
and poor psychological health has been shown previously in war veterans to
persist for several decades after their war experiences
(Branchey et al, 1984;
Hunt & Robbins, 2001). It
is yet to be seen whether the patterns of increased psychological disorders
demonstrated in 1991 Gulf War veterans will be replicated in the recent
veterans of the 2003 Iraq War. The potential costs in terms of human suffering
highlight the need to maintain access to effective mental health care for all
veteran populations.
Despite extensive training already undertaken by many military personnel, our findings also suggest that some Defence Force members need to be even better prepared for the hostile, uncertain environment of future war zones. The question arises, however, as to whether it is even possible to fully prepare a soldier for the array of potential war-zone experiences. If improved methods of preparation cannot be achieved, it may be inevitable that the legacy of poor psychological health following war exposure will continue into the future, to repeat the patterns of the past.
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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Received for publication September 24, 2003. Revision received March 24, 2004. Accepted for publication April 5, 2004.