title: Longitudinal Analyses of Presenteeism and Its Role as a Predictor of Sick Leave in Patients With Ankylosing Spondylitis.
abstract: OBJECTIVE
  To investigate, in a cohort of patients with ankylosing spondylitis (AS) adequately treated with infliximab, changes over time in presenteeism and the role of presenteeism relative to that of the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the Bath Ankylosing Spondylitis Functional Index (BASFI) in predicting sick leave.
  
  
  METHODS
  Data were analyzed from 71 patients with paid work and taking a stable dose of infliximab participating in a 96-week study with 5 assessment points. Covariates included presenteeism, sick leave, time, sex, age, BASDAI, BASFI, Bath Ankylosing Spondylitis Metrology Index, and part- or full-time work. Presenteeism represented the AS impact on productivity (by visual analog scale, range 0-10, where 10 = completely unproductive). Sick leave represented the number of days absent from work due to AS in the last 6 months. A linear mixed-effects model for presenteeism, and hurdle and zero-inflated count models for sick leave were explored.
  
  
  RESULTS
  Mean ± SD presenteeism ranged from 2.2 ± 2.2 to 3.8 ± 7.8, and sick leave occurred in 8-17% of the patients during the 6-month period. Presenteeism positively correlated with BASDAI and BASFI, but was not significantly influenced by time. The chance of incurring sick leave was affected by presenteeism but not by BASDAI and BASFI. Conditional on being absent from work, the effect of presenteeism on the length of sick leave (in days) was much stronger than BASDAI and BASFI. For presenteeism ≥5, an increase of 1 unit in presenteeism yielded an increase by 36-40% (or 2-12 days) in the length of sick leave during the following 6 months.
  
  
  CONCLUSIONS
  Presenteeism, even measured by a simple visual analog scale, was an important factor to explain future sick leave.
authors.affiliation: Maastricht University Medical Center, Maastricht, and University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: An
authors.initials: A
authors.lastname: Tran-Duy
authors.affiliation: Hasselt University, Diepenbeek, Belgium.
authors.forename: Thien T V
authors.initials: TT
authors.lastname: Nguyen
authors.affiliation: Hasselt University, Diepenbeek, Belgium.
authors.forename: Herbert
authors.initials: H
authors.lastname: Thijs
authors.affiliation: Rheumazentrum Ruhrgebiet, Herne, Germany.
authors.forename: Xenofon
authors.initials: X
authors.lastname: Baraliakos
authors.affiliation: Rheumazentrum Ruhrgebiet, Herne, Germany.
authors.forename: Frank
authors.initials: F
authors.lastname: Heldmann
authors.affiliation: Rheumazentrum Ruhrgebiet, Herne, Germany.
authors.forename: Juergen
authors.initials: J
authors.lastname: Braun
authors.affiliation: Maastricht University Medical Center, Maastricht, The Netherlands.
authors.forename: Annelies
authors.initials: A
authors.lastname: Boonen
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D000069597:Presenteeism / Q000639:trends*; D018582:Sick Leave / Q000639:trends*; D013167:Spondylitis, Ankylosing / Q000175:diagnosis* / Q000453:epidemiology*