title: Lifetime asymptomatic for back pain: the validity of self-report measures in soldiers.
abstract: METHODS
  A 5-year prospective observational study in US Army Reserve soldiers.
  
  
  OBJECTIVE
  The aims of this study were 2-fold: to evaluate the prevalence of soldiers reporting no previous back pain (BP) on 3 consecutive annual assessments, and to compare these findings to those obtained from a subsequent monthly detailed BP assessment.
  
  
  BACKGROUND
  BP history is a risk factor for future BP and disability. Conversely, subjects reporting a negative history of back troubles are thought to be at low risk for future BP events. Reporting of previous BP is assumed to have high validity. Few studies have critically evaluated the validity of the self-reported "lifetime asymptomatic" status in civilian or military populations.
  
  
  METHODS
  Two hundred eighty-five special operations reserve soldiers were queried annually using standardized US Army Medical Questionnaires, among whom 154 (54%) reported no BP or history thereof over 3 consecutive years. Over the next 18 months these soldiers completed annual US Army Medical Questionnaires, as well as monthly numerical rating scale pain scores, Oswestry Disability Indexes, and questions regarding back injuries. At the study's conclusion, soldiers again completed the annual medical certificate, and the results of this final BP assessment were compared with those from monthly surveillance reports.
  
  
  RESULTS
  During monthly surveillance of purported "lifetime asymptomatic" soldiers, the 18-month cumulative percentages reporting BP scores > or = 2, > or = 4, and > or = 6 were 84%, 64%, and 14%, respectively. For Oswestry Disability Index scores, these percentages were 25% for scores > or = 10, and 12% for scores > or = 20. Yet, at the conclusion of the 5-year study, 97% soldiers still described themselves as being "asymptomatic for BP problems."
  
  
  CONCLUSIONS
  In physically active soldiers self-identified as without back problems, the report of BP using frequent surveillance tools is extremely common. The overwhelming majority of these soldiers appeared to have high resilience to common BP episodes (i.e., returned to usual duties). Episodic BP should be considered a normative rather than exceptional occurrence. Similar to other conditions, long-interval surveys of BP history may underestimate the true prevalence of BP.
authors.affiliation: Department of Orthopedic Surgery, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: Eugene J
authors.initials: EJ
authors.lastname: Carragee
authors.forename: Steven P
authors.initials: SP
authors.lastname: Cohen
mesh_terms: D000328:Adult; D001416:Back Pain / Q000453:epidemiology* / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008889:Military Personnel / Q000706:statistics & numerical data*; D010147:Pain Measurement / Q000379:methods; D015995:Prevalence; D011446:Prospective Studies; D015203:Reproducibility of Results; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology