Hope M. Tiesman, MSPH, PhD

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Injuries in the US Army Commonalities
Generalizability to Civilian Injury Research

• Hope M. Tiesman, MSPH, PhD
• Fellow CDC/NIOSH/DSR
• Adjunct Faculty WVU
• WVU ICRC
• Public Health Grand Rounds
• February 6, 2008

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Overview

• Injury Research
• Military Injury Research the TAIHOD
• Gender Differences in Occupational
  Non-Occupational Injuries in the US Army
• Incidence of Re-Injury in the US Army A
  Retrospective Cohort Study of Risk Factors
• The Effects of Re-injury on Military Discharge
  from the US Army

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Acknowledgments

• Corinne Peek-Asa
• Craig Zwerling
• Jim Torner
• Ginger Yang
• Nancy Sprince
• Paul Amoroso
• Paul Whitten
• Heartland Center for Occupational Health Safety
• University of Iowa Injury Prevention Research
  Center

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• The more pain or suffering something causes, the
  more we tend to fear it the cleaner or at least
  quicker the death, the less it troubles us. "We
  dread anything that poses a greater risk for
  cancer more than the things that injure us in a
  traditional way, like an auto crash.

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1996 YPLL vs. Federal Research Investment
(IOM-1998)
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Why ???

• 1. Injuries due to random uncontrollable
  factors
• 2. Prevention challenging due to powerful vested
  interests
• 3. Lack of information interest in injury
  prevention
• 4. Injury data limited

Injury Prevention Public Health-T.Christoffel
SS Gallagher
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Injury Data Issues

• International Classification of Diseases
• Nature of Injury or N codes (skull fracture)
• 800-999 Injury Poisoning
• External Cause of Injury or E codes (fall from or
  on stairs or steps)
• No national requirement for E-codes on hospital
  discharge data forms
• 50 of medical records have enough info to code
  place of occurrence (work relatedness)

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Total Army Injury Health Outcomes Database
(TAIHOD)
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Advantages of TAHIOD Injury

• ICD-9 Code (800-999)
• STANAG injury coding system
• Trauma code (intent duty-relatedness)
• Battle related, intentional inflicted non-battle,
  off-duty, schemes exercises, scheduled
  training, on-duty, unknown
• Injury Code (activity or cause)

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Trauma Code

• Battle Wound/Injury
• Direct result of action
• Other battle casualties
• Intentionally Inflicted Non-Battle Injuries
• Assault
• Intentionally self-inflicted
• Accidental Injury
• Off-duty
• Schemes exercises
• Other scheduled training
• On-duty
• Unknown

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Trauma Code - On-Duty

• Physically present at any location where they are
  to perform work
• Includes lunch, coffee and rest breaks
• Parking lot
• Being transported by DOD or command conveyance to
  perform officially assigned work
• Reimbursable or non-reimbursable travel for
  performing duty
• Not routine travel to and from work

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Trauma Code

• Off-Duty
• Departed duty station at end of normal work
  schedule
• On leave or liberty
• Scheduled Training
• Initial Entry Training (8 weeks)
• Advanced Individual Training
• Schemes Exercises
• Field exercises
• Military Simulations

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Example

• ICD-9CM code
• 800-804 (Fracture of Skull)
• 800.1 Closed with cerebral laceration and
  contusion
• Trauma Code
• 5 off-duty
• Injury Code
• 100 Non-milInjury is to driver of motor
  vehicle
• 101 Non-milInjury is to passenger of motor
  vehicle
• 102 Non-milInjury is to unspecified occupant
  of mv
• 103 Non-milBoarding from vehicle
• 104 Non-milInjury is to pedestrian
• 105 Non-milInjury is to pedal cyclist
• 106 Non-milInjury is to motorcyclist
• 107 Non-milDriver/rider on tracked/semi
  tracked veh.
• 109 Non-milInjury is to other or unspecified
  person

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Military Injuries

• Leading cause of morbidity mortality for US
  Armed Forces
• Leading causes of injury MVC, falls,
  sports/athletics

Writer JV. AJPM 200018(3)
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Generalizability

• Off-duty
• drive cars, ride bikes, play sports, misc
• 72 of enlisted population has job with
  corresponding civilian job titles

Sulsky SI. JOEM 200345(3)
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Proposed Cohort - TAIHOD
No disability related discharge
Categorized Re-injury OR No Re-injury
Cohort with acute, traumatic injury in first 11
months of service
Disability-related discharge
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Gender Differences in Occupational
Non-Occupational Injuries

• Significant correlations between recreational
  injuries having a work-place injury
• Trends not well described with respect to gender
  or occupation
• Majority of military injury research focuses on
  initial entry training

Tiesman HM, Peek-Asa C, Zwerling C, Sprince
NL, Amoroso PJ. Occupational
Non-Occupational Injuries in the US Army Focus
on Gender. AJPM 2007 33(6).
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Retrospective Cohort

• Outcomes
• Injuries
• Re-injuries
• Disability discharges

• Inclusion Criteria
• AD between 1/1992 12/2002
• hospitalized injury via primary diagnosis
  (ICD-9CM 800-959.8)
• injury occurred in first 11 months of service
• Off-duty, schemes exercises, scheduled
  training, on-duty, unknown

Followed till 12/31/2002
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Methods

• Injury Variables
• External cause of injury
• ISS (calculated with ICD-MAP)
• Sum of squares of most severely injured body
  parts
• days in hospital
• Demographics
• Gender, age, education
• Pay grade (Enlisted Officers/Warrant Officers)
• Occupation (12 DoD Career Management Fields)
• infantry, electrical equipment repair,
  communications intelligence, health care,
  technical allied specialties, support
  administration, electronic mechanical equipment
  repair, craft workers, service supply,
  non-occupational enlisted, unknown, officer

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Analysis

• Cross-sectional analysis
• Injury Rates
• Denominator data via DMDC (mid-yr estimates)
• Compared with Rate Ratios (RRs) 95 CIs
• Injuries compared via Pearson chi-squares,
  Fishers exact, t-tests
• Stratified by gender
• P-values adjusted using the Bonferroni correction

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Retrospective Cohort
5,678 soldiers 4,879 men (86) 792 women
(14) 4,051 Caucasian (71) 1,627 Non-Caucasian
(29) 5,441 Enlisted (96) 237 Officers
(4) Average age 21.4 (sd3.2)
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Results Crude Injury Rates
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Duty-Status by Gender
Training plt0.0001, On-duty p0.01, Schemes
p0.006, Off-duty p0.23
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Selected Causes of Off-Duty Injuries by Gender
p0.001 athletics and sports, p0.017 - fighting
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Selected Causes of On-Duty Injuries by Gender
p0.0016 Falls
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ISS Hospital Days by Gender
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Conclusions

• Findings consistent with current research
• Scheduled training most dangerous injury risk
  period for women
• Off-duty No differences in frequency, sig.
  differences in injury causes
• On-duty job tasks within job categories appear
  to be gender specific
• Women longer hospital stays, though injuries not
  more severe
• Special attention paid to mens off-duty injuries

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Strengths Limitations

• Strengths
• TAIHOD database
• Large cohort of mixed occupations
• Limitations
• Confounding
• Out-patient injuries
• Unknown trauma code

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Incidence of Re-Injury in the US Army A
Retrospective Cohort Study of Risk Factors

• Defining re-injury complicated
• distinction between acute chronic injury
• Musculoskeletal conditions
• 75 caused by old injury or injuries
• Identify risk factors calculate incidence rates
  for re-injury in cohort of AD Army personnel with
  an early-career hospitalized injury

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Musculoskeletal Conditions (710-739)

• 717 Internal Derangement of Knee
• 733 Other Disorders of Bone and Cartilage,
• 715 Osteoarthrosis and Allied Disorders
• 716 Other and Unspecified Arthropathies
• 718 Other Derangement of Joint
• 719 Other and Unspecified Disorders of Joint
• 721 Spondylosis and Allied Disorders
• 722 Intervertebral Disc Disorders
• 723 Other Disorders of Cervical Region
• 724 Other and Unspecified Disorders of Back
• 726 Peripheral Enthesopathies and Allied
  Syndromes
• 727 Other disorders of Synovium, Tendon, and
  Bursa
• 728 Other Disorder of Muscle, Liagament, and
  Fascia
• 729 Other Disorders of Soft Tissues
• 730 Osteomyelitis, Periostitis, other
  infections of Bone
• 732 Osteochondropathies
• 733 Other Disorders of Bone and Cartilage
• 736 Other Acquired Deformities of Limbs
• 737Curvature of Spine

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Retrospective Cohort
5,661 followed 337 soldiers injured 329
soldiers re-injured
5,678 soldiers 4,879 men (86) 792 women
(14) 4,051 Caucasian (71) 1,627 Non-Caucasian
(29) 5,441 Enlisted (96) 237 Officers
(4) Average age 21.4 (sd3.2)
Average follow-up 2.7 yrs (sd2.5 yrs)
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Methods

• Retrospective Cohort previously described
• followed to all future hospitalizations
  (12/31/2002)
• excluded 17 soldiers who died from initial injury
  
• Definition of Re-injury
• 1 day between discharge for 1st injury
  admission for re-injury
• ICD-9 code for re-injury same as ICD code for 1st
  injury (n74)
• ICD-9 code for re-injury corresponded with code
  for 1st injury (n36)
• musculoskeletal conditions associated with 1st
  injury (n219)

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Methods Re-injury

• ICD-9 code for re-injury same as code for 1st
  event (n74)
• ICD-9 code for re-injury associated with 1st
  event (n36)
• (844)Sprains Strains of Knee and Leg
  (836)Dislocation of Knee
• Musculoskeletal conditions associated with 1st
  event (n219)
• (717)Internal Derangement of Knee

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219 (67) Soldiers with a musculoskeletal
hospitalization
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Statistical Analysis

• Injury rates calculated compared using Relative
  Risks (RR) 95 CI
• Survival analysis measure risk of a hospitalized
  re-injury
• Hazard Ratios (HRs) 95CI
• Multivariate Cox proportional hazards regression
  model
• Person-time was date of discharge from 1st injury
• admission date of re-injury hospitalization
• date of discharge from military
• end of the follow-up period
• confounders those associated w/ re-injury or
  based on prior research

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Results

• 287 (87) had 1 re-injury hospitalization
• Fracture most common (n46, 14)
• Avg. time between discharge admission of
  re-injury was 281 days (sd394 days)
• 42 occurred within 3 months of first injury
• Traumatic injuries had a significantly shorter
  time between 1st injury re-injury (144.2 days
  versus 350.9 days plt0.0001)

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Results Re-injury Rates
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Hazard Ratios (95 CI)s
Controlling for gender, age, marital status,
education, time in hospital for first injury

• No enlisted group at increased risk
• Occupational injuries not at increased risk
  (HR0.97, NS)
• No causes of injury at increased risk, after
  controlling for injury type body part injured

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Conclusions

• incidence rate of re-injury much higher than
  civilian re-injury rates (23.4/1000)
• socio-demographic factors less importance-RFs
  for re-injury related to first injury
• injuries to knee, upper extremity, back
• dislocations, sprains/strains
• re-injuries resulted in longer average hospital
  stays

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Conclusions

• Disadvantages
• musculoskeletal conditions related to original
  injury?
• bias of the one day difference-medical
  continuation of first injury not a separate
  event?
• Advantages
• only study examining variety of re-injuries in
  large diverse cohort, with extensive follow-up
• did not use self-reported injuries
• data collection was comprehensive

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The Effects of Re-injury on Military Discharge
from the US Army

• Military disability rates rising
• 1/5 partly disabled due to service in Iraq
  Afghanistan
• Difficult to determine role of injuries in
  disability discharge 50
• Re-injury significant outcome for
  physically-active groups
• Investigate role of re-injury on physical
  disability discharge
• male female soldiers
• nature of re-injury

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Identifying Injury-Related Disability

• Disability Agencies
• Physical Evaluation Boards
• Medical Evaluation Boards
• VASRD - diagnostic codes for a wide spectrum of
  diseases physical impairments covering all
  major body systems

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Medical conditions associated with disability
(1994)
Army
Orthopedic/
musculoskeletal
53.1
Mental disorders
14.2
Neurologic/convulsive
12.1
Systemic/respiratory
7.4
Blood/skin/endocrine
3.3
Cardiovascular system
3.4
Digestive system
2.9
Visual/auditory conditions
1.7
Total Number
6,382
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Categories of Disability

• Permanent disability a permanent disability
  resulting in discharge with full compensation.
• Separation with severance pay disability
  resulting in discharge with separation pay.
• Separation without benefits disability
  resulting in discharge without pay
• Temporary disability a medical disability that
  could change over time not fit for active duty
• Fit for duty return for active duty

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Disability in the Armed Forces
Discharge from active duty with or without
compensation

• Permanent disability
• Temporary disability

Not fit for active duty
To be re-evaluated over time
Discharge Return to Duty
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Methods

• Retrospective cohort design described
  previously
• Primary Risk Factor
• re-injury hospitalization after discharge for 1st
  event (n329)
• Outcome
• discharge from the Army, due to physical
  disabilities
• Physical disability, entitled to severance pay,
  no retirement
• Mandatory retirement required by law due to
  temporary disability
• Mandatory retirement, permanent physical
  disability
• Involuntary discharge, physical disability not
  otherwise covered
• Involuntary discharge, physical disability,
  resulted from intentional misconduct, no
  severance pay
• Previously retired, entitled to recomputation of
  retirement pay, aggravate physical disability

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Analysis

• Possible Confounders
• demographics
• DoD occupation code
• body region
• type of initial injury
• work-relatedness
• nature of re-injury
• Survival Analysis
• Cox Proportional Hazards Regression
• Kaplan-Meier estimates of survival
• Log-rank tests for equality

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Results - Univariate

• 977 (17) physical disability discharge
• 3,336 (59) discharged for other reason
• Females, those not married, enlisted soldiers
  significantly more likely to be discharged
  (plt0.0001)
• Soldiers in health care occupations had highest
  proportion receiving a disability discharge (49)
  (plt0.0001)

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Results - Univariate

• Those with sprains and strains most likely to be
  discharged (plt0.001)
• Those with knee injuries most likely to be
  discharged (plt0.001)
• On-duty injuries slightly more likely to result
  in discharge (p0.07)

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Survival curves for disability discharge, by
re-injury status
log-rank test, plt0.0001
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Survival curves for disability discharge, by
re-injury status - Females
Log rank test p0.14
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Survival curves for disability discharge, by
re-injury status - Males
Log rank test, p0.0003
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Multivariate analysis for disability discharge,
stratified by gender
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Conclusions

• Re-injury, regardless of nature, sig. risk factor
  for pre-mature military discharge
• Soldiers with a re-injury 34 more likely to be
  discharged from the Army, after controlling for
  confounders (Men - 36, Women 20)
• On-duty injuries associated with military
  discharge (HR1.28, 1.05-1.56)
• Prospective cohort could fully examine
  relationships between injury, re-injury and
  disability

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Strengths Limitations

• Limitations
• relationship between disability discharge
  injury
• analysis of re-injury not feasible
• Misclassification of the exposure
• No data on rehab services
• Strengths
• large diverse cohort over long period
• control for known confounders

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Final Thoughts

• Purposes
• describe epi. of early career hospitalized
  injuries
• Follow injured soldiers to re-injury
• describe role of re-injury in discharge from
  military service
• Results point towards need for prospective cohort
  studies provide direction for military injury
  prevention programs
• Not realistic to expect that soldiers operate in
  a 100 risk-free environment

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Questions?