Prior depression and incident back pain among military registered nurses: A retrospective cohort study.

BACKGROUND: Occupational back pain rates are substantial among registered nurses, and nurses also report high rates of depression. The role of depression as a potential predictor of back pain among nurses appears understudied.

OBJECTIVES: The objective of the study was to determine whether a history of depression predicted incident back pain in a population of military registered nurses when controlling for relevant risk factors.

DESIGN: We employed a retrospective cohort approach using longitudinal data in which gender-specific subject groups were followed from the beginning of duty as a registered nurse to the occurrence of an outcome, or to censoring due to completion of service or the end of available data.

PARTICIPANTS: This study included all United States Army registered nurses who began work during 2011-2014 without evidence of prior back pain in clinical records.

METHODS: Data from automatically-collected medical and administrative sources were combined and used to provide 2134 person-years of observation on 1248 individuals. These data were organized at the person-month level in a panel data structure to support discrete-time multivariable logistic regression models. The models examined the relationships between prior depression, Body Mass Index, the presence of prior combat duty and selected control variables and the outcome, the incident occurrence of back pain.

RESULTS: The incidence rate of back pain was 18.6 per 100 person-years and the period prevalence was 31.7%. Prior depression was a statistically-significant predictor of incident back pain among female subjects (odds ratio [OR]: 1.75, 95% confidence interval [CI]: 1.08-2.83, P-value<0.05). Body Mass Index of 30kg/m2 or greater, prior combat deployments, and age 36 years or older was each associated with back pain for male and female nurses.

CONCLUSIONS: The study's findings provide the first evidence of a temporal link between antecedent depression and later back pain among female military nurses. High Body Mass Index was found to be a further, modifiable risk factor for back pain in this population.