title: The relationship between smoking and knee osteoarthritis in the Osteoarthritis Initiative.
abstract: OBJECTIVE
  To estimate the extent that smoking history is associated with symptoms and disease progression among individuals with radiographically confirmed knee Osteoarthritis (OA).
  
  
  METHODS
  Both cross-sectional (baseline) and longitudinal studies employed data from the Osteoarthritis Initiative (OAI) (n = 2250 participants). Smoking history was assessed at baseline with 44% current or former smokers. The Western Ontario and McMaster Universities Arthritis Index (WOMAC) was used to measure knee pain, stiffness, and physical function. Disease progression was measured using joint space width (JSW). We used adjusted multivariable linear models to examine the relationship between smoking status and exposure in pack years (PY) with symptoms and JSW at baseline. Changes in symptoms and JSW over time were further assessed.
  
  
  RESULTS
  In cross-sectional analyses, compared to never-smokers high PY (≥15 PY) was associated with slightly greater pain (beta 0.36, 95% CI: 0.01-0.71) and stiffness (beta 0.20, 95% CI: 0.03-0.37); and low PY (<15 PY) was associated with better JSW (beta 0.15, 95% CI: 0.02-0.28). Current smoking was associated with greater pain (beta 0.59, 95% CI: 0.04-1.15) compared to never-smokers. These associations were not confirmed in the longitudinal study. Longitudinally, no associations were found between high or low PY or baseline smoking status with changes in symptoms (at 72 months) or JSW (at 48 months).
  
  
  CONCLUSIONS
  Cross-sectional findings are likely due residual confounding. The more robust longitudinal analysis found no associations between smoking status and symptoms or JSW. Long-term smoking provides no benefits to knee OA patients while exposing them to other well-documented serious health risks.
authors.affiliation: Department of Quantitative Health Sciences, University of Massachusetts Medical School, Worcester, MA 01655, USA. Electronic address: catherine.dube@umassmed.edu.
authors.forename: C E
authors.initials: CE
authors.lastname: Dubé
authors.affiliation: Department of Quantitative Health Sciences, University of Massachusetts Medical School, Worcester, MA 01655, USA. Electronic address: ShaoHsien.Liu@umassmed.edu.
authors.forename: S-H
authors.initials: SH
authors.lastname: Liu
authors.affiliation: Division of Rheumatology, Tufts Medical Center, Boston, MA 02111, USA. Electronic address: Jeffrey.Driban@tufts.edu.
authors.forename: J B
authors.initials: JB
authors.lastname: Driban
authors.affiliation: Division of Rheumatology, Tufts Medical Center, Boston, MA 02111, USA. Electronic address: tmcalindon@tuftsmedicalcenter.org.
authors.forename: T E
authors.initials: TE
authors.lastname: McAlindon
authors.affiliation: Center for Primary Care and Prevention, Memorial Hospital of Rhode Island, Pawtucket, RI 02860, USA; Department of Family Medicine, Warren Alpert Medical School, School of Public Health, Brown University, Providence, RI 02912, USA; Department of Epidemiology, Warren Alpert Medical School, School of Public Health, Brown University, Providence, RI 02912, USA. Electronic address: CEaton@careNE.org.
authors.forename: C B
authors.initials: CB
authors.lastname: Eaton
authors.affiliation: Department of Quantitative Health Sciences, University of Massachusetts Medical School, Worcester, MA 01655, USA. Electronic address: Kate.Lapane@umassmed.edu.
authors.forename: K L
authors.initials: KL
authors.lastname: Lapane
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D010147:Pain Measurement / Q000379:methods; D012720:Severity of Illness Index; D012907:Smoking / Q000009:adverse effects* / Q000453:epidemiology; D012959:Socioeconomic Factors; D014481:United States / Q000453:epidemiology; D055815:Young Adult
keywords: Knee osteoarthritis; Osteoarthritis Initiative; Smoking