MILITARY MEDICINE, 171, 3:253, 2006
The Neurocognition Deployment Health Study: A Prospective
Cohort Study of Army Soldiers
Guarantor: Jennifer J, Vasterling, PhD
Contributors: Jennifer J, Vasterling, PhD*t; Susan P. Proctor, DSc^P; COL Paul Amoroso, MC USA^;
Robert Kane, PhDp; Col Gary Gackstetter, USAF BSC**; CDR Margaret A, K. Ryan, MC USNft;
Matthew J. Friedman, MD h
Questions remain regarding the effects of military operational
deployment on health. The Neurocognition Deployment
Healtli Study addresses several gaps in the deployment health
literature, including lack of baseline health data, reliance on
subjective measures of exposure and health variables, pro-
longed intervals between redeployment and health assess-
ments, and lack of a uniform case definition. The Neurocogni-
tion Deployment Health Study uses a prospective cohort
design to assess neuropsychological outcomes associated
with Iraq deplojmient. Methods incorporate administration of
performance-based neuropsychological measures to Army sol-
diers before and after Iraq deployment and to nondeployed
Army Soldiers assessed during comparable periods of garrison
duty. Findings should have the potential to delineate neuro-
psychological outcomes related to combat theater deplojonent
and to identify potential risk and protective factors related to
T T nexplained health symptoms appear to be ubiquitous in
LJ modem war.' However, questions remain regarding link-
ages between military operational deployment and the develop-
ment of physical or mental health symptoms. Unresolved issues
include whether subjective complaints correspond to objectively
measured health indices; whether health problems can be
linked to specific environmental exposures, stress exposures, or
other deployment-related experiences; and the interaction of
deployment with potential risk and resilience factors for health.
The Neurocognition Deployment Health Study (NDHS) is a col-
laboration between the Department of Defense (DoD) and the
Department of Veterans Mfairs (VA), designed to examine a
specific health outcome domain (i.e., neuropsychological func-
•Veterans Mairs Medical Center, New Orleans, LA 70112.
tDepartment of Psychiatry and Neurology, Tulane University School of Medicine,
New Orleans, LA 70112.
fVeterans Affairs Boston Healthcare System, Boston, MA 02130,
§Department of Environmental Health, Boston University School of Public Health,
Boston, MA 02118,
^U,S, Army Research Institute of Environmental Medicine, Natick, MA 01760,
[Baltimore Veterans Affairs Medical Center, Veterans Affairs Maryland Health Care
System, Baltimore, MD 21201,
#Department of Neurology, University of Maryland School of Medicine, Baltimore,
"Uniformed Services University of the Health Sciences, Bethesda, MD 20814,
ttNaval Health Research Center, San Diego, CA,
iJDartmouth Medical School, Hanover, NH 03755,
§§National Center for PTSD, Department of Veterans Affairs, White River Junction,
The content of this article does not necessarily reflect the position or policy of the
government, and no official endorsement should be inferred.
This manuscript was received for review in October 2004 and was accepted for
publication in April 2005,
tioning) after combat-zone deployment. The study incorporates
prospective administration of performance-based measures of
neuropsychological functioning to cohorts of Army soldiers de-
ploying in support of Operation Iraqi Freedom, A comparison
group of Army Soldiers is assessed bef'ore and after an interval of
The primary objectives of this ongoing study are (1) to exam-
ine the impact of combat-zone deployment on neuropsycholog-
ical outcomes, including neurobehavioral and emotional func-
tioning, (2) to examine the impact of deployment-related stress
and environmental exposures on neuropsychological outcomes,
and (3) to identify potential health risk and protective factors
relevant to neuropsychological outcomes. Although post-trau-
matic stress disorder (PTSD) and depression are measured pri-
marily as potential risk factors for neuropsychological compro-
mise, the study design also permits PTSD and depression
screening measures to be treated as outcome variables. There-
fore, a secondary objective of the study is to describe select
psychiatric outcomes, the importance of which is suggested by
high rates of PTSD and other psychiatric disorders after Iraq
Why Neuropsychological Outcomes?
Neuropsychological functioning encompasses cognitive (e.g.,
memory, attention, and reasoning), perceptual-sensory-motor
(e,g,, motor speed), and emotional (e,g., mood) behaviors
thought to reflect neural integrity. Much of the deployment
health literature stems from the 1991 Gulf War (GW), after
which significant subsets of military personnel and veterans
reported nonspecific health (e.g,, headache and fatigue) and
cognitive (e.g., memory impairment) symptoms suggesting pos-
sible neural dysfunction,^^ For example, 24,1% of individuals in
the VA GW Registry Health Examination Program and 36.2% of
individuals in the DoD Comprehensive Clinical Evaluation Pro-
gram complained of memory impairment, making it the fourth
most prevalent complaint in both registries,^ Neuropsychologi-
cal dysfunction may negatively affect occupational functioning
via mechanisms such as reduced performance efficiency, com-
promised decision-making, distractibility, and increased error
rates.^"'" Therefore, from phenomenological and occupational
perspectives, neuropsychological dysfunction is central to the
concerns of military personnel.
From a theoretical perspective, certain aspects of neuro-
psychological functioning would be expected to be sensitive to
potential deployment experiences, including neurotoxicant
and traumatic stress exposures. The cluster of symptoms
reported by some GW returnees overlaps partially with neu-
rotoxic syndromes,'^"'' and recent work revealed that a small
Military Medicine, Vol. 171, March 2006
group of GW participants endorsing health symptoms showed
abnormalities on neuroimaging studies.'^ Similarly, emo-
tional sequelae of war-zone stress exposures have been linked
to neuropsychological dysfunction among GW veterans.'^"^'
Regarding feasibility, neuropsychological assessments can be
conducted without physical discomfort, invasive methods, or
expensive technology, rendering neuropsychological assess-
ment a safe, portable, and cost-effective means of estimating
neural health. Moreover, neuropsychological functioning can be
measured by using standardized, performance-based instru-
ments that facilitate reliable, repeatable, and objective measure-
Current Gaps in the Deployment Health Literature
Although health problems have been documented after mili-
tary conflicts dating from the U.S. Civil War,^^ public conscious-
ness regarding war-related illnesses peaked after the 1991 GW.
This led to the establishment of DoD and VA clinical health
registries'*'^^ and, as recommended by the 1994 National Insti-
tutes of Health Technology Assessment Workshop,^'* large-scale
epidemiological studies examining the effects of GW deployment
on health.^'^'^'^^^^ However, much remains unknown about
health and military deployment because of limitations of the
existing literature, including (1) lack of baseline health data; (2)
reliance on subjective, self-report measures of exposure and
health outcome variables; (3) health assessments generally con-
ducted long after redeployment (i.e., return from the deploy-
ment); and (4) absence of a uniform case definition. The follow-
ing sections discuss the impact of these issues.
One of the most frequently cited and perhaps most significant
obstacles to interpreting health outcome data from the 1991 GW
is the lack of information regarding the health of GW veterans
before deployment to the Gulf region.^''"^^ Without knowledge of
baseline health status, it is difficult to determine whether health
symptoms reported after redeployment are attributable to de-
ployment or instead reflect preexisting conditions. This problem
is exacerbated when self-reported symptoms are "unexplained"
because they are not linked to a specific etiology, resulting in
potential clinician biases in etiological inference and treatment
decisions.^^ The failure to conduct baseline assessments also
limits identification of risk and protective factors present before
deployment that may moderate the impact of deployment on
In addition to advancing scientific understanding of deploy-
ment health issues, accurate chronological attribution of symp-
tom onset and identification of risk and protective factors carry
significant administrative and health care policy implications.
For example, an understanding of whether specific health con-
ditions were caused or exacerbated by military service poten-
tially affects disability, pension, and compensation decisions
within DoD and VA. Similarly, the identification of risk and
protective factors holds promise to enhance health outcomes via
systems-based prevention programs, when risk can be modi-
fied, and via direction of treatment efforts, when risk cannot be
Objective Exposure and Outcome Indices
Environmental hazards, psychological stress, and hazard-
stress interactions have been proposed as contributors to neu-
ropsychological dysfunction among GW veterans.^^ However,
the literature also suggests that neuropsychological and health
problems self-reported by deployed GW veterans may not be
unique to GW service.'•^•^•^^•^^ This controversy centers on in-
complete documentation of GW exposures to exogenous health
hazards. A number of toxicants have been postulated as etio-
logical factors for GW-related health and cognitive problems,
including organophosphate pesticides and chemical warfare
agents, solvents, smoke from burning oil wells, and pyridostig-
mine bromide.'"' However, with rare exceptions (e.g., smoke from
oil wells), exposure levels for known toxicants have been difficult
to document retrospectively, and some war-zone toxic expo-
sures may remain unknown. Although self-reports have been
used in the deployment health literature as proxies for objective
exposure data, self-reported GW environmental exposures have
proved to be over-reported or unreliable over time,'"''^ As a
result, exposure-symptom relationships have been difficult to
Most epidemiological studies examining health outcomes
have relied on self-reports of health and cognitive symptoms.
Although cognitive impairments (e.g., concentration and mem-
ory problems) are among the most common complaints of GW
retumees'''^^'^'''''^ and have distinguished deployed and nonde-
ployed samples,^ self-reported symptoms do not necessarily cor-
respond to objective measures of neuropsychological function-
ing. That is, indices of cognitive dysfunction based solely on
self-reports are vulnerable to subjective biases and may there-
fore diverge from performance-based measures.'^•^^''^
Several studies have attempted to address this issue by ex-
amining performance on neuropsychological tasks among GW
veterans. These efforts yielded inconclusive findings but re-
vealed mild cognitive impairment among some GW subsets.
Whereas some studies found that neuropsychological perfor-
mance deficits among GW veterans were more strongly related
to emotional factors than to war-zone variables,'^•'^'''^'''' others
suggested that neuropsychological deficits were associated with
illness variables'*^'^' and self-reported exposure to war-zone
neurotoxicants.^''^^'^^ Although inconclusive and subject to the
limitations discussed above regarding the lack of baseline and
exposure data, such studies point to the potential utility of
combining prospectively assessed, objective, neuropsychologi-
cal data with objectively verified exposure data.
Assessment of Health Outcomes Proximal to Redeployment
Intervals between redeployment and health assessment
among GW veterans, with rare exceptions,^-^^ often spanned
several years. For example, GW veterans were assessed 4 years
after redeployment in the Iowa Persian Gulf Study,^ 6 years after
their return in a large U.K. epidemiological study,*^ 5 years after
redeployment in phase I of the National Health Survey of Gulf
Era Veterans and Their Families,^ and 6 years after redeploy-
ment in the Canadian GW Forces Study.^'' Although these and
Military Medicine, Vol. 171, March 2006
similar studies provide valuable information about some of the
longer-term health outcomes of GW veterans and may allow
examination of health problems that manifest slowly, a pro-
longed interval between redeployment and assessment permits
the introduction of intervening variables that may also nega-
tively affect health. Furthermore, the health effects of some
environmental exposures may dissipate over time and become
more difficult to detect as the initial exposure becomes more
distant. Therefore, postdeployment health assessments are ide-
ally first conducted soon after redeployment, with repeated as-
sessments to allow detection of more slowly developing condi-
Lack of Uniform Case Definitions
Attempts to define deployment-related illnesses have often
adopted a syndromic approach. However, in the context of un-
explained health symptoms following military deployments,
such approaches have important limitations. For example, after
the 1991 GW, attempts were made to define a syndrome; how-
ever, no consistent symptom pattern emerged across individu-
als or studies.'* Although certain symptoms (e,g,, muscle and
joint pain) were commonly reported, no single cluster of symp-
toms emerged in a consistent manner. Similarly, deployment
health researchers defined illness differently across studies,
leading to ambiguities regarding the comparability of findings.
One potential solution to this problem is to establish a consis-
tent case definition. However, a single-case definition approach
may be of limited utility when multiple etiologies are present and
multiple biological systems are affected. A second potential ap-
proach is to focus on associations between specific exposures
and theoretically related outcome domains.
The NDHS uses a prospective cohort design in which Army
Soldiers are assessed before Iraq deployment and again within
90 days after redeployment and are compared with nondeployed
Army Soldiers assessed once before and once after a comparable
period of nondeployment. Because of the continual rotation of
forces into the combat theater, it is likely that all military units
participating in the study, including nondeploying comparison
groups, will eventually deploy. However, study participation of
the nondeploying comparison group is limited to a period of
garrison duty, and nondeploying units include only those that
have not previously deployed to Iraq. Using a modification of the
categorization procedure reported by Blood and Aboumrad,^^
the design also includes stratification according to unit type
(e,g,, combat arms, combat support, or combat service support)
and duty status (i.e., active duty or reservist).
Sampling is conducted at the battalion unit level, with battal-
ions selected to refiect specific unit types, as described above.
The units sampled are anticipated to refiect varying duties,
stress exposures, and geographic locations during deployment.
The target sample size of 1,550 refiects oversampling of deploy-
ing Soldiers (target n = 850), relative to nondeploying Soldiers
(target n = 700), The decision to oversample deploying Soldiers
was based on power calculations, taking into account planned
analyses within the deployed sample that examine the relative
impact of deployment-related variables, as well as different at-
trition rates between the deploying and nondeploying Soldiers,
Unit identification is conducted by U,S. Army Forces Command.
Inclusion criteria for individual participants include member-
ship in one of the units identified according to the criteria listed
above and willingness to participate. Exclusion criteria include
physical injuries or disabilities precluding ability to complete
the questionnaires, to see the test stimuli, or to respond to the
computer by button-press. Battalion leaders are asked to refer
potential participants at random, facilitating inclusion of a rep-
resentative range of individual ranks, ages, educational back-
grounds, and military occupational specialties (MOSs) from
each battalion. Refusals and individuaJs not completing both
assessments are tabulated for subsequent analyses of response
and longitudinal participation rates.
Tables I (primary data collection measures) and II (secondary
data obtained from military records) provide a summary of the
variables to be examined and the sources for obtaining data.
Variables fall into three categories, i,e,, (1) vulnerability or resil-
ience factors (e,g., previous stress exposure, occupational expe-
rience, cognitive readiness, predeployment health status, and
health perception), (2) deployment factors (e.g., deployment sta-
tus, environmental and stress exposures, and duties), and (3)
neuropsychological outcomes. The consistent finding that only
subgroups of deployed personnel experience health and cogni-
tive impairments after war zone participation emphasizes the
need for statistical models that include potential vulnerability
and resilience factors as covariates.
We attempted to streamline the assessment battery to the
degree possible without compromising the major objectives of
the work. Although issues of respondent burden are always
relevant to data quality, the threshold for overtaxing respon-
dents may be particularly low during preparation for deploy-
ment and soon after redeployment. The assessment battery in-
cludes a survey of relevant demographic, neuromedical, and
historical information; questionnaires assessing stress expo-
sure, emotional distress, and health perception; and perfor-
mance-based neuropsychological tests. Table I provides a sum-
mary of variables derived from the battery.
Survey of Relevant Demograpliic, Neuromedical, and Htstorical
The Time 1 assessment includes a brief survey recording
participant age, handedness, race/ethnicity, gender, education,
rank, MOS, deployment and occupational history, and presence
or absence of risk factors for neurocognitive dysfunction, in-
cluding developmental disorders, seizure disorders, head in-
jury, neurotoxicant exposure, and other neurological and med-
ical disorders thoughts to affect brain functions. In addition,
current alcohol and medication consumption, current and his-
torical use of antimalarial medication, and history of emotional
or psychiatric disorders are recorded. During the Time 2 assess-
ment, current alcohol and medication usage is reassessed, as is
Military Medicine. Vol, 171. March 2006
256 The NDHS
Personal history information
Demographic information, health risk behaviors, military information, neurological and
developmental disorders, previous neurotoxicant exposure, diagnosis and treatment
history of psychiatric and past alcohol use disorders, current medications, history of
head injury, and antimalarial medications
Stress exposure, deployment risk and resilience factors, emotional distress, and health
Life stress before deployment (DRRI)
Perception of unit cohesion (Dfyy)
Perception of training as related to preparedness (DRRIl
Perception of deployment environment (DRRI)
Life and family concerns (DRRI)
Deployment concerns (DfJRI)
Combat stress (DRRI)
Postbattle experiences (DRRI)
Self-reported exposure to nuclear, biological, and chemical agents (DRRI)
Perception of health [V/SF12)
Self-reported cognitive functioning (Medical Outcomes Study CF)
PTSD symptom severity (PCL)
State affective disturbance (POMS)
WMS Visual Reproductions (visual learning and memory)
WMS-III Verbal Paired Associates (verbal learning and memory)
Trail-Making Test, parts A and B (attention and working memory, respectively)
NES3 Continuous Performance Test (sustained attention/vigilance)
Stanford Sleepiness Scale (alertness/sleepiness)
Simple Reaction Time (processing speed)
Mathematical Processing (working memory/computational skills)
Logical Reasoning-Symbolic (grammatical reasoning)
Code Substitution Learning (learning)
Code Substitution Delay (memory)
Running Memory (working memory)
Tapping (fine motor speed)
Matching to Sample (visual memory)
Test of Memory and Malingering
Questionnaire and interview
DRRI, Deployment Risk and Resilience Inventory; V/SF12, Medical Outcomes Study Short Form 12; CF, Cognitive Functioning Scale; PCL, PTSD
Checklist; POMS, Profile of Mood States; CES-D, Center for Epidemiological Studies Depression Inventory; WMS, Wechsler Memory Scale; NES3,
Neurobehavioral Evaluation System, Ed, 3; ANAM, Automated Neuropsychological Assessment Metrics.
any new development (since Time 1) of emotional disorders or
neuromedical risk factors. Verification of this information is
obtained from review of available service and medical records, as
list,^° a 17-item checklist that queries for frequency of each of
the Diagnostic and Statistical Manual of Mental Disorders, Ed.
4, PTSD diagnostic symptoms. Persistent mood disturbance is
measured at Time 2 with the 9-item version of the Center for
Epidemiological Studies Depression Inventory. ^''^^ Health per-
ception is measured in Time 1 and Time 2 assessments with the
Medical Outcomes Study Short Form 12,^3,64 g i2-item scale
adapted for use among military veterans and containing somatic
and emotional health subscales, and the Medical Outcomes
Study Cognitive Functioning Scale,^^ a 4-item scale assessing
perception of cognitive functions such as concentration, deci-
sion-making, and memory,
Stress Exposures, Emotional Distress, and Health Perception
Stress exposures, emotional distress, and health perception
are measured with self-report inventories. However, we also link
self-reported stress exposure information to objective indices of
combat exposures, as available on a military unit basis. Stress
exposures are measured with a modified version of the Deploy-
ment Risk and Resilience Inventory,'^ a modular inventory with
strong psychometric properties that was developed after the GW
to capture events common to contemporary war-zone deploy-
ment. State affect and PTSD symptoms are measured during
Time 1 and Time 2 assessments with the Profile of Mood
States,^^ a 50-item adjective checklist, and the PTSD Check-
Performance-Based Neuropsychological Tests
Administered in its entirety at both Time 1 and Time 2 as-
sessments, the performance-based neuropsychological battery
was designed to include (1) measures that might be expected to
Military Medicine, Vol. 171, March 2006
MEDiCAL AND MILITARY RECORD DATA
Documented medical conditions, immunization history, and
hospital and clinic visits
ICD-9-CM-coded diagnoses (for brain and nervous system
disorders) from inpatient and outpatient records for the time
period starting 1 year (12 months) before the Time 1
assessment through the Time 2 assessment
Anthrax vaccination(s) and date(s) of inoculation
Prescription medication usage and type for the time period
between Time 1 and Time 2 assessments
Personal military service history information
Prior military deployment history
Historical rank and occupational specialty information
Armed Forces Qualification Test scores from testing performed
upon entry into the service (generally available only for
During-deployment medical surveillance information, i.e., ICD-9-
CM-coded diagnoses (for brain and nervous system
disorders) documented in theater
Deployment environmental exposure and geographic location
Environmental exposure data
Unit location information (geographic coordinate information)
over time and locale while in theater
1CD-9-CM, International Classification of Diseases, Ninth Revision,
remain stable in the face of either neurotoxicant or stress expo-
sures, (2) measures sensitive to neurotoxicant exposures, and
(3) measures sensitive to stress-related emotional disturbances.
The battery was designed to emphasize measurement sensitivity
to a greater extent than specificity, and there is some overlap of
neuropsychological domains thought to be affected by neuro-
toxicant exposures and stress (e.g., attention, working memory,
and initial acquisition on anterograde memory tests). However,
measures were also included (e.g., motor functioning, process-
ing speed, visuospatial processing, and memory retention) that
might be expected to differentiate neurotoxic sequelae from
those related to psychological distress.
To increase experimenter reliability and to facilitate adminis-
tration and data management efficiency, most tasks are admin-
istered in a computer-assisted format and are drawn primarily
from the Automated Neuropsychological Assessment Metrics^*
and the Neurobehavioral Evaluation System, Ed. 3.^^'^^ Each of
these batteries has undergone considerable psychometric devel-
opment and has shown acceptable levels of reliability and con-
struct validity.®^"^'' Moreover, each contains tasks developed
specifically for assessment of the neurocognitive sequelae of
hazardous environmental exposures.''^'^" Table I lists Auto-
mated Neuropsychological Assessment Metrics and Neurobe-
havioral Evaluation System subtests included in the assess-
Non-computer-administered, standardized, neuropsycholog-
ical, performance-based tasks are also included, to allow re-
sponses in modalities other than button press (Table I). These
include Trail-Making Test parts A and B,^^ Wechsler Memory
Scale, 3rd Ed.,^^ Verbal Paired Associates, and Wechsler Mem-
ory Scale^^ Visual Reproductions, which were selected because
of their sensitivity to neurotoxicant exposures.*""^^ Trial 1 of the
Test of Memory and Malingering*^ is administered as an objec-
tive index of motivation.
Health and Military Service Record Information
Recognizing the important contributions of deployment med-
ical surveillance information to research investigations,^ we
ask participants for permission to request information from
medical/health records maintained in DoD computer-based or
automated databases. We obtain pharmacy and medical diag-
nostic information from automated military health care record
system databases containing information derived from inpatient
and outpatient visits during military service for the period be-
ginning 12 months before the Soldier's study participation and
ending with the Time 2 assessment. Also, anthrax vaccination
records are requested. We request from the DoD Defense Man-
power Data Center Armed Forces Qualification Test scores (as a
measure of basic academic skills obtained upon entry into ser-
vice), personal military deployment history, historical rank, and
MOS information (see Table II for a summary of information
derived from electronic databases).
Objective Deployment Exposures
Since the 1991 GW, the U.S. Army Center for Health Promo-
tion and Preventive Medicine has collected air, water, and soil
measures of various toxicants (i.e., metals, volatile organic com-
pounds, and particulate matter) in areas worldwide where there
are U.S. deployment missions. In addition, geographic location
information can be used as ancillary data for potential deploy-
ment-related experiences and exposures.^^ As indicated in Table
II, environmental exposure data and unit geographic location
information are acquired from the Center for Health Promotion
and Preventive Medicine as available.
Potential participants are briefed individually and undergo
consent procedures conducted by civilian study personnel, pro-
viding written informed consent before engaging in the study. As
part of the consent process, participants are asked if they wish
to be contacted again for future studies, allowing for extended
longitudinal follow-up monitoring. To protect confidentiality, we
do not disclose a Soldier's willingness or refusal to participate to
other military personnel, including anyone within the Soldier's
unit or chain of command. At each study site, an impartial
ombudsman (i.e., someone not cormected with the study or in
the soldier's chain of command) is available to respond to ques-
tions or concems about the study. Human subject consider-
ations have been reviewed and approved by the Army Surgeon
General Human Subjects Research Review Board, the Tulane
University Health Sciences Center institutional review board,
and local VA committees associated with the principal investi-
Assessments are conducted at the military installations. The
paper-and-pencil questionnaires and neuropsychological tests
Military Medicine, Vol. 171, March 2006
are administered by a civilian data collection team, comprised
primarily of licensed clinicians and other health care personnel
who have completed masters or doctoral level training. The time
per participant averages 75 minutes for Time 1 assessments
and 85 minutes for Time 2 assessments. The performance-
based neuropsychological measures are individually adminis-
tered, including the computerized measures, which are exam-
iner-assisted. Closed-system headphone sets are used to allow
verbal communication between the examiner and study partic-
ipant while minimizing ambient noise. Paper-and-pencil sur-
veys are completed in small groups (i,e,, 8-12 participants).
Data Analysis Plan
Primary research questions will be examined via two ap-
proaches. First, we will use repeated-measures multilevel anal-
ysis to examine potential interactions addressing whether de-
ployed and nondeployed soldiers differ in baseline and
postdeployment measures of neuropsychological functioning.
Second, we will use multivariate regression analysis to identify
the relative contributions of deployment-related variables (e.g.,
stress and environmental exposures, unit type, and geographic
location) and potential risk factors (e.g., individual difference
variables, predeployment health variables, and cognitive perfor-
mance) to postdeployment outcome measures.
Although the past decade has led to increased understanding
of possible deployment health effects, considerable gaps in
knowledge remain. The ongoing NDHS was initiated in February
2003 to address some of the limitations of past deployment
health research, including the absence of prospective health
assessments, over-reliance on subjective measures of exposure
and outcome variables, prolonged intervals between redeploy-
ment and outcomes assessment, and the lack of a uniform case
The NDHS examines neuropsychological functioning before
deployment and again after redeployment among Iraq-deploying
Army soldiers. The prospective design holds potential to assess
changes ih neuropsychological functioning over the period of
deployment, to identify potential preexisting variables that may
serve to increase risk or resilience, and to minimize possible
retrospective reporting biases. The postdeployment assessment
is conducted within 90 days after redeployment, minimizing the
impact of intervening factors developing in the interval between
redeployment and assessment and maximizing the sensitivity of
the assessment to health problems that develop as a result of
deployment exposures that are most potent proximal to their
occurrence. Although the current protocol does not extend be-
yond the initial postdeployment assessment, the cohort design,
combined with consent for future assessments, allows for lon-
gitudinal extension. Such follow-up monitoring, if conducted,
will allow examination of the stability of health outcome mea-
sures and the possible longer-term health consequences of de-
The inclusion of both deploying and nondeploying groups
allows examination of variables related to the passage of time vs.
deployment. The nondeploying comparison groups are selected
to match, as closely as possible, the deploying study groups in
terms of individual and unit military characteristics. It can be
speculated that most of the nondeploying units included in the
study will also eventually deploy. However, their study partici-
pation is limited to assessment before and after a period of
garrison duty, thus allowing them to serve initially as an appro-
priate nondeployed comparison sample. The inclusion within
groups (deployed and nondeployed) of different unit types (com-
bat arms, combat support, and combat service support) will
likely allow variations in both the geographic distribution and
types of missions performed by Soldier participants during Iraq
deployment. The inclusion of both regular active duty and re-
servist Soldiers increases the representativeness of the sample
for the larger Iraq-deploying military population and allows ex-
amination of duty type as a predictive variable.
The choice of neuropsychological functioning as a primary
outcome focus reflects consideration of several factors. First, the
neuropsychological outcome domain has a theoretical and phe-
nomenological basis relative to deployment health effects and
the biological systems that may be affected by hypothesized
deployment-related exposures. Second, neuropsychological im-
pairment has significant implications for occupational function-
ing. Finally, neuropsychological functioning can be measured
with objective, performance-based measures that are portable
and cost-effective. The secondary mental health outcome do-
main reflects disorders (i,e,, PTSD and depression) highly likely
to develop following stress exposures associated with Iraq de-
ployment^ and linked to neuropsychological dysfunction in mil-
itary veteran^^-83 and civilian^^-^^ samples. The inclusion of ob-
jective environmental exposure data will help address past gaps
in the literature related to failure to document or to verify pos-
sible hazardous environmental and occupational exposures.
In summary, this ongoing study, although restricted to a
somewhat narrow range of health outcomes, addresses some of
the gaps in knowledge inherent to the existing deployment
health literature. It is the first relatively large-scale effort to
assess deployment health using a prospective cohort design
with primary data collection of objective outcome measures. It is
hoped that the findings of this study will complement those
produced by large, prospective, survey-based, cohort studies
such as the Millennium Cohort Study,^'' The NDHS also serves
as an additional model of successful DoD-VA collaboration and
of prospective primary data collection of health-related out-
comes. Future research will build on this effort by including
other service branches, examining additional outcomes, and
extending the longitudinal assessment beyond a single fol-
We thank LTC David Brand, COL Peter Garibaldi, and COL Gerald
Cross (Ret.) for their guidance and facilitation in the initiation of this
study. We are gratefut for the ongoing assistance provided by U.S. Forces
Command, Command Surgeon's Office, Special appreciation is extended
to Dr, Stephen Grate, U,S, Army Medical Research and Materiel Com-
mand, for his continual effort and support. We also appreciate the assis-
tance and encouragement provided by COL Karl Friedl, Commander. U.S,
Army Research Institute of Environmental Medicine, and the DoD De-
ployment Health Support Directorate,
This work was supported by U,S, Army Medical Research and Materiel
Command (DAMD 17-03-0020), a VA Medical Research Service Award,
and the South Central (Veterans Integrated Service Network 16) Mental
Military Medicine, Vol, 171, March 2006
Illness, Research, Education, and Clinical Center, The U,S. Army Medical
Research Acquisition Activity (Fort Detrick, Maryland) is the awarding
and administering acquisition office for DAMD 17-03-0020.
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