Background Musculoskeletal (MSK) injuries are a leading cause of morbidity among US Army soldiers, especially among women and the newly enlisted. While extremes of body mass index (BMI), low physical fitness and tobacco use have been identified as risk factors, no prior studies have determined the combined effects of these risk factors or tested for gender differences in the associations.
Methods We conducted a retrospective cohort study utilising the Stanford Military Data Repository to study all enlisted soldier accessions to the US Army between January 2011 and January 2014, with follow-up through December 2014 (n=238 772). We used discrete-time logistic regression to test for associations between demographic, socioeconomic and health behaviour-related predictors and incident lower extremity injuries. We included interaction terms to test for gender differences.
Results Among men, there were greater adjusted odds of injury among underweight (OR 1.27), overweight (OR 1.14) and obese soldiers (OR 1.54) (all p<0.001) relative to normal-weight soldiers. No statistically significant differences in the odds of injury on the basis of BMI were observed for female soldiers. Physical fitness was a significantly stronger predictor of injury for female as compared with male soldiers, while the association between tobacco use and injury was stronger for men (OR 1.47) than for women (OR 1.30) (p<0.001 for both).
Conclusion This is the largest known study to simultaneously assess important, modifiable musculoskeletal injury risk factors and to test for gender differences in these associations. These findings provide critical gender-related nuances for clinicians and leaders seeking to reduce the risk of these problems.
- cohort study
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Contributors DAN and LMK were responsible for data acquisition and analysis. All the authors contributed substantially to study conceptualisation and design. All authors interpreted the data, drafted the manuscript and approved the final version for publication.
Funding This study was supported by a grant from the US Army Medical Department Advanced Medical Technology Initiative, which had no role in study design; collection, analysis or interpretation of data; writing the report or the decision to submit the report for publication.
Disclaimer The views expressed in this article are those of the authors and do not reflect the views or official policies of the US Government, the Department of Defense, the Defense Health Agency, the Department of the Army or the US Army Medical Command.
Competing interests None declared.
Patient consent Not required.
Ethics approval Stanford University IRB and Defense Health Agency Human Research Protection Office.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Access to data in the Stanford Military Data Repository is restricted per the Data Sharing Agreement with the Defense Health Agency. All results described in the manuscript are provided in the main tables.