title: Incidence and course of low back pain episodes in the general population.
abstract: METHODS
  Population-based, prospective cohort.
  
  
  OBJECTIVE
  To estimate incidence and course of severity-graded low back pain (LBP) episodes in adults.
  
  
  BACKGROUND
  Past studies report variable estimates that do not differentiate LBP severity.
  
  
  METHODS
  An incidence cohort of 318 subjects free of LBP and a course cohort of 792 prevalent cases was formed from respondents to a mailed survey. Incident, recurrent, persistent, aggravated, improved, and resolved episodes were defined by the Chronic Pain Questionnaire. The follow-up at 6 and 12 months was 74% and 62%, respectfully. Annual estimates were age and sex standardized.
  
  
  RESULTS
  The cumulative incidence was 18.6% (95% confidence interval [CI], 14.2%-23.0%). Most LBP episodes were mild. Only 1.0% (95% CI, 0.0%-2.2%) developed intense and 0.4% (95% CI, 0.0%-1.0%) developed disabling LBP. Resolution occurred in 26.8% (95% CI, 23.7%-30.0%), and 40.2% (95% CI, 36.7%-43.8%) of episodes persisted. The severity of LBP increased for 14.2% (95% CI, 11.5%-16.8%) and improved for 36.1% (95% CI, 29.7%-42.2%). Of those that recovered, 28.7% (95% CI, 21.2%-36.2%)had a recurrence within 6months,and 82.4% of it was mild LBP. Younger subjects were less likely to have persistent LBP (incidence rate ratio, 0.88; 95% CI, 0.80-0.97) and more likely to have resolution (incidence rate ratio, 1.26; 95% CI, 1.02-1.56).
  
  
  CONCLUSIONS
  Most new and recurrent LBP episodes are mild. Less than one third of cases resolve annually, and more than 20% recur within 6 months. LBP episodes are more recurrent and persistent in older adults.
authors.affiliation: Division of Outcomes and Population Health, Toronto Western Hospital Research Institute, University Health Network, Toronto, Ontario, Canada. dcassidy@uhnres.utoronto.ca
authors.forename: J David
authors.initials: JD
authors.lastname: Cassidy
authors.forename: Pierre
authors.initials: P
authors.lastname: Côté
authors.forename: Linda J
authors.initials: LJ
authors.lastname: Carroll
authors.forename: Vicki
authors.initials: V
authors.lastname: Kristman
mesh_terms: D000328:Adult; D000367:Age Factors; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D017116:Low Back Pain / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012737:Sex Factors; D013997:Time Factors