Risk factors for back-related disability in the US army and marine corps

Study Design: Matched case-control epidemiological study. Objective: To identify pre-enlistment, demographic, and service-related risk factors for back-related disability in enlisted US soldiers and Marines comparing those who were deployed with those who did not deploy during the service term. Summary of Background Data: Back conditions are a major cause of morbidity and lost work days in both the US working population and military. Back-related conditions are among the most prevalent causes of military disability discharge but little research has been conducted to identify risk factors for back-related disabilities in this population. Methods: Cases included enlisted Army and Marine Corps service members evaluated for back-related disability. Controls, frequency matched by year of military entrance and service, were selected from the enlisted service member population. Pre-enlistment demographic and medical characteristics, deployment, and ambulatory care data collected from existing military databases were used. Crude and adjusted odds of back-related disability were modeled using conditional logistic regression. Results: In adjusted models, service members who were overweight (odds ratio [OR]: 1.17; 95% confidence interval [95% CI]: 1.12-1.23) and obese (OR: 1.35; 95% CI: 1.26-1.44), between ages 25 and 29 years (OR: 1.23; 95% CI: 1.16-1.31), or 30 years or older (OR: 1.43; 95% CI: 1.34-1.52) at military entrance were at increased odds of a back-related disability. History of a back diagnosis at the pre-enlistment medical examination (OR: 1.94; 95% CI: 1.50-2.50) and deploying once (OR: 1.09; 95% CI: 1.05-1.14) were also associated with increased odds of a back-related disability. Conclusion: Enlisted soldiers and marines with back-related disabilities were more likely to be older, have a higher body mass index, have a history of pre-enlistment back conditions, and were deployed once, compared with controls without a back-related disability. Additional research is necessary to further examine the complex relationship between deployment to combat zones, onset of musculoskeletal symptoms, and back-related disability in soldiers and marines.