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The authors ask you:
Background
The Biomechanics Branch, US Air Force (AF) Research Laboratory, leads the Department
of Defense in research focused on injury prevention for aircrew members. With
the addition of an occupational epidemiologist, the Branch is now positioned
to identify non-aircrew occupational categories at increased risk for injury
and illness. Once identified, biomechanical engineers, and others, will explore
causes and solutions to decrease identified hazards.
Approach
Electronically available demographic and occupational data have been linked
to inpatient and outpatient injury and illness data to assemble a historical
prospective cohort. Univariate methods were used to describe the data, which
were stratified by rank (officer and enlisted) and gender. Cox’s proportional
hazards analyses were used to produce adjusted hazard ratios for the association
between AF occupations and hospitalizations for injuries and illnesses.
Results
Injury and musculoskeletal disorder hospitalization data have undergone preliminary
analysis, with a number of occupations at increased risk identified.
Conclusions
Teaming occupational epidemiology with experienced biomechanical engineers has
significant potential to reduce occupational injuries and illnesses within the
AF workplace.
The US Air Force (AF) is decreasing the number of Airmen retained on active duty, but continues to have a high operational tempo in support of ongoing operations in Iraq and Afghanistan. As a result, active duty AF personnel (Airmen) are being pushed to their limits. In fact, General Moseley, the AF Chief of Staff, recently described an Airman’s time as a “critical commodity”. Yet lost duty day injuries have been estimated to be between 0.4 and 2.6 injuries per 1,000 Airmen per year.1 Similarly, approximately one out of every 100 Airmen per month are placed on limited duty for one or more days due to an unspecified injury.2 With Airmen working at maximum pace, there is now an increased need to understand the causes of occupational injuries and illnesses, and develop mitigation strategies.
Currently, there is no centralized agency within the AF that focuses on occupational injury and illness reduction. The US Air Force Safety Center has established a mishap reporting system that collects data on most mishaps that result in one or more lost work days. Although this organization has the ability to conduct epidemiological studies of occupational injuries, it lacks the ability to conduct focused studies to identify underlying causes and apply multi-disciplinary resources to develop plans of action to reduce occupational injuries and illnesses.
The Biomechanics Branch at the Air Force Research Laboratory has a long-standing tradition of transitioning basic research into operational products that improve the safety of Airmen who perform flight-related duties. Leveraging previous successes, and with the addition of an occupational epidemiological capability, the Biomechanics Branch will undertake a series of studies to identify Airmen at increased risk of occupational injury or illness. Airmen identified at increased risk for occupational injuries or illnesses will be further studied to identify leading occupational hazards, with the goal of developing actionable plans to reduce injury or illness occurrence.
This project utilizes a multidisciplinary approach including epidemiologists, biostatisticians, biomechanical engineers and anthropometrists. The team will identify Airmen at increased risk for occupational injuries and illnesses, and then conduct workplace investigations to identify specific hazards and develop solutions. Figure 1 provides an overview of this process.
Figure 1. Overview of US Air Force Injury and Illness Study, 2001-2005
Population
Electronically-available demographic and military-specific data were obtained from the Defense Manpower Data Center (DMDC) for all Airmen serving on active duty for six or more months during the period of October 1, 2001 through December 31, 2005. Individual-level data includes personal identifiers, date of birth, gender, race/ethnicity, marital status, education, rank, occupational specialty, inclusive dates of service, and duty locations. Additional demographic and military-specific data are available from the Air Force Personnel Center, and may provide more detail on specific occupations, such as aircraft flown and number of accrued flight hours.
Outcomes
International Classification of Diseases, Ninth Revision, Clinical Modifications (ICD-9-CM) coded electronic inpatient and outpatient health data were obtained from the Military Health System (MHS). The MHS maintains a data repository for the DoD, and this source was used to identify Airmen with hospitalizations or outpatient visits during the study period. Data obtained from the MHS included personal identifiers, ICD-9-CM coded diagnoses, and direct costs for each visit. Additionally, disabled Airmen may be identified using a disability file provided by the DMDC. This file includes all Airmen who received disability payments during the study period. A summary of the data sources and analytic database assembly process is illustrated in Figure 2.
Figure 2. Assembly of the injury and illness database from electronically-available demographic, military-specific, occupational and duty information, all of which is linked to health outcomes and disability data.
Analyses
Analyses will be stratified into four groups, including male officers, female officers, male enlisted, and female enlisted. Univariate analyses, including chi-square and t-tests will be performed to assess the significance of associations between injury outcome categories and occupational specialty. An exploratory model analysis will be completed to assess regression diagnostics, significant associations, and possible confounding, while simultaneously adjusting for all other variables in the model. We use Cox’s proportional hazards time-to-event modelling to calculate hazard ratios for the association between occupational status and outcomes of interest for Airmen, while accounting for attrition from and delayed entry into the AF over the follow-up period. Outcomes of interest for this study include hospitalizations and outpatient visits for musculoskeletal disorders (ICD-9-CM 710-739), injury and poisoning (ICD-9-CM 800-999), direct costs, and veterans’ disability payments. SAS Version 9.1.3 (SAS Institute, Inc., Cary NC) is used for all data analyses. This study was approved by the governing Institutional Review Board prior to collecting any data.
Epidemiological analyses are ongoing at this time. Preliminary analyses have been completed for hospitalization diagnoses for the broad ICD-9-CM categories of musculoskeletal disorders and injury and poisoning. Compared to their respective referent groups, male medical officers, and enlisted male aircrew, battlefield airmen, maintenance, supply, civil engineering, or security forces, and female enlisted civil engineering or security forces were at significantly increased risk for musculoskeletal disorder hospitalizations. Results were similar for injury and poisoning hospitalizations in that male officers working in operations or medical specialties, in addition to male enlisted Airmen working in aircrew, battlefield airmen, maintenance, electronics, supply, civil engineering, security forces, or medical, and female enlisted Airmen working in supply or civil engineering specialties were at significantly increased risk compared to their respective referent groups.
The Biomechanics Branch at the Air Force Research Laboratory is uniquely positioned within the AF to identify Airmen at increased risk for occupational injuries and illnesses. To date, a number of occupational specialties have been identified as being potential candidates for more in-depth workplace investigations that will draw heavily on in-house specialties, including biomechanics and anthropometry.
Epidemiological analyses will continue to better describe occupational categories at increased risk for injury. Future efforts include analyses of the disability data and similar analyses for AF civilian employees. Although comprehensive data are lacking for civilian employees, worker’s compensation data are available, and will be the outcome of interest. Finally, the Air Force Safety Center collects detailed mishap report information that may be useful when conducting workplace investigations.
The findings and conclusions in this poster are those of the author(s) and do not necessarily represent the views of the National Institute for Occupational Safety and Health. Citations to Web sites external to NIOSH do not constitute NIOSH endorsement of the sponsoring organizations or their programs or products. Furthermore, NIOSH is not responsible for the content of these Web sites.
