Association Between Predeployment Optimism and Onset of Postdeployment Pain in US Army Soldiers

IMPORTANCE: Pain after deployment is a major health care concern. While risk factors have been previously studied, few studies have explored protective factors. OBJECTIVE: To examine the prospective association between predeployment optimism and the onset of new pain after deployment in US Army soldiers. DESIGN, SETTING, AND PARTICIPANTS: This prospective longitudinal cohort study examined US Army soldiers (active duty, Reserve, and National Guard) who deployed to Afghanistan or Iraq between February 12, 2010, and August 29, 2014, and completed the necessary psychological and health assessments before and after deployment. Analyses were performed in the Person-Event Data Environment between July 2016 and November 2018. This study relied exclusively on existing, secondary Army data. Of the 413 763 Army soldiers who met the specified deployment criteria, 385 925 soldiers were missing 1 or more of the required assessment forms. Of the remaining 27 838 soldiers who were examined for eligibility, 7104 soldiers were excluded because of preexisting back pain, joint pain, or frequent headaches. These exclusions resulted in a final analytic sample of 20 734 eligible soldiers. MAIN OUTCOMES AND MEASURES: This study examined new reports of pain after deployment, including new back pain, joint pain, and frequent headaches. RESULTS: Among 20 734 US Army soldiers (87.8% male; mean [SD] age, 29.06 [8.42] years), 37.3% reported pain in at least 1 new area of the body after deployment: 25.3% reported new back pain, 23.1% reported new joint pain, and 12.1% reported new frequent headaches. As a continuous measure, each 1-U increase in optimism was associated with 11% lower odds of reporting any new pain after deployment, even while adjusting for demographic, military, and combat factors (odds ratio, 0.89; 95% CI, 0.86-0.93). Tertile analyses revealed that compared with soldiers with high optimism (lowest odds of new pain) soldiers with low optimism had 35% greater odds of reporting new pain in any of the 3 sites evaluated (odds ratio, 1.35; 95% CI, 1.21-1.50). In addition, a larger increase in risk of new pain was observed when comparing the moderate-optimism and low-optimism groups rather than the high-optimism and moderate-optimism groups. CONCLUSIONS AND RELEVANCE: Higher levels of optimism were associated with lower odds of reporting new pain after deployment, over and above other common determinants of pain, including demographic and military characteristics and combat experiences. Soldiers with low levels of optimism before deployment could benefit from programs geared toward enhancing optimism.