MILITARY MEDICINE, 176, 11:1320, 2011
1320 MILITARY MEDICINE, Vol. 176, November 2011
Lumbar degenerative disc disease (DDD) is a progressive con-
dition that exists along a continuum of pathologic processes.
From desiccation of the nucleus pulposus, to annular tearing,
diffuse disc bulging, and disc space collapse, the degenerative
process can occur over the course of decades, culminating in
substantial debilitation. 1,2 Symptoms of DDD, including back
pain and/or radiculopathy, can limit work and productivity.
Additionally, the cost of treating this condition is especially
high, with an estimated 30 to 50 billion health care dollars
spent on managing degenerative spinal processes annually. 1
Over the course of the 20th century, medicine’s under-
standing of DDD has evolved considerably. 3 Nonetheless, the
etiology and natural history of this condition remain poorly
understood. 1–3 Challenges to the effective investigation of DDD
include the lack of a standardized defi nition for the condition, as
well as disparities in study populations that inhibit comparisons
between published works. 3,4 Moreover, researchers recognize
that DDD can occur as a natural part of aging, and it may be dif-
fi cult to draw morphologic distinctions between expected senile
changes within the disc and pathologic processes. 4–6 Indeed, sev-
eral investigations have documented morphologically degenera-
tive discs in as many as 72% of asymptomatic subjects. 7–10
Genetic factors 1–4,11 , heredity 3,4,11 , age 3–6,11–14 , sex 3,11,15 ,
race 3,11 , level of physical activity 3,5,6,11–20 , smoking 6,21 , and body
habitus 1,3,11,22 have all been proposed as potential factors in the
development of lumbar DDD. Although some investigations
have focused on the prevalence of this condition, as well as
risks implicated in its development, the incidence of lumbar
DDD has not previously been estimated for a young, high-
The population of the U.S. Armed Forces is an ideal group
in which to study lumbar DDD. Compared to the general
population, military service members represent a younger
cohort with higher physical demands, who must maintain
weight requirements, and pass semiannual physical fi tness
tests. Additionally, all members of the Armed Forces must
pass an entry physical, where conditions such as DDD or spi-
nal abnormalities are screened. Individuals with pre-existing
DDD would, for the most part, be excluded from initial entry
into the U.S. military.
Perhaps, most importantly, in terms of epidemiologic
research, the military operates on a closed medical system
where all conditions for which service members are treated
are documented by International Classifi cation of Diseases,
Ninth Revision, Clinical Modifi cation (ICD-9-CM) code in
the medical record. Diagnoses made at military facilities or in
nonmilitary consultations are captured by the system. 23,24
Diagnoses are collected from the medical records of service
members and stored in the Defense Medical Epidemiology
Database (DMED). 24 The DMED contains data for individuals
according to ICD-9-CM diagnosis and can stratify patients by
sex, race, military rank, branch of service, and age. The data-
base can also be utilized to accurately determine the number
of service members within the U.S. military during any given
year. The DMED has been successfully used in the past to
investigate the incidence and epidemiology of several orthope-
dic conditions within the American military population. 25–29
Incidence and Risk Factors for Lumbar Degenerative Disc
Disease in the United States Military 1999–2008
MAJ Andrew J. Schoenfeld , MC USA * ; CPT James H. Nelson , MC USA * ;
COL Robert Burks , MC USA † ; LTC Philip J. Belmont Jr., MC USA *
ABSTRACT The epidemiology of lumbar degenerative disc disease (DDD) is poorly understood, and the incidence of
this disorder has not previously been characterized for a young, physically active population. This study sought to evalu-
ate the incidence of lumbar DDD, and identify risk factors for its development, among individuals serving in the U.S.
military over a 10-year period. The Defense Medical Epidemiology Database was queried for the years 1999–2008 using
the International Classifi cation of Diseases, Ninth Revision, Clinical Modifi cation code for lumbar disc degeneration
(722.52). Overall incidence was determined and multivariate Poisson regression analysis was performed to identify risk
factors among demographic characteristics such as age, sex, race, military rank, and branch of service.
White race, female sex, Army, Air Force, or Marine service, enlisted positions within the ranks, and age were found
to be signifi cant risk factors for the development of lumbar disc degeneration. Increased age appeared to be one of the
most important risk factors, with adjusted incidence rates successively increasing for each age group under study. The
incidence of lumbar DDD in this young, racially diverse, and physically active population is higher than most other
* Department of Orthopedic Surgery, William Beaumont Army Medical
Center, 5005 North Piedras Street, El Paso, TX 79920.
† Naval Postgraduate School, 1 University Circle, Monterey, CA 93943.
All authors are employees of the U.S. Federal Government and the U.S.
Army. The opinions or assertions contained herein are the private views of
the authors and are not to be construed as offi cial or refl ecting the views of
William Beaumont Army Medical Center, the Department of Defense, or
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