title: Heterogeneity and event dependence in the analysis of sickness absence.
abstract: BACKGROUND
  Sickness absence (SA) is an important social, economic and public health issue. Identifying and understanding the determinants, whether biological, regulatory or, health services-related, of variability in SA duration is essential for better management of SA. The conditional frailty model (CFM) is useful when repeated SA events occur within the same individual, as it allows simultaneous analysis of event dependence and heterogeneity due to unknown, unmeasured, or unmeasurable factors. However, its use may encounter computational limitations when applied to very large data sets, as may frequently occur in the analysis of SA duration.
  
  
  METHODS
  To overcome the computational issue, we propose a Poisson-based conditional frailty model (CFPM) for repeated SA events that accounts for both event dependence and heterogeneity. To demonstrate the usefulness of the model proposed in the SA duration context, we used data from all non-work-related SA episodes that occurred in Catalonia (Spain) in 2007, initiated by either a diagnosis of neoplasm or mental and behavioral disorders.
  
  
  RESULTS
  As expected, the CFPM results were very similar to those of the CFM for both diagnosis groups. The CPU time for the CFPM was substantially shorter than the CFM.
  
  
  CONCLUSIONS
  The CFPM is an suitable alternative to the CFM in survival analysis with recurrent events, especially with large databases.
authors.affiliation: Department of Experimental and Health Sciences, Center for Research in Occupational Health (CiSAL), Universitat Pompeu Fabra (UPF), C/Doctor Aiguader 88, Barcelona 08003, Spain. jmiguel.martinez@upf.edu.
authors.forename: Isabel
authors.initials: I
authors.lastname: Torá-Rocamora
authors.forename: David
authors.initials: D
authors.lastname: Gimeno
authors.forename: George
authors.initials: G
authors.lastname: Delclos
authors.forename: Fernando G
authors.initials: FG
authors.lastname: Benavides
authors.forename: Rafael
authors.initials: R
authors.lastname: Manzanera
authors.forename: Josefina
authors.initials: J
authors.lastname: Jardí
authors.forename: Constança
authors.initials: C
authors.lastname: Alberti
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Yasui
authors.forename: José Miguel
authors.initials: JM
authors.lastname: Martínez
mesh_terms: D000041:Absenteeism; D000293:Adolescent; D000328:Adult; D000465:Algorithms; D005260:Female; D006801:Humans; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology; D008875:Middle Aged; D015233:Models, Statistical; D009369:Neoplasms / Q000453:epidemiology; D009790:Occupations; D016012:Poisson Distribution; D016016:Proportional Hazards Models; D012044:Regression Analysis; D013030:Spain; D016019:Survival Analysis; D055815:Young Adult
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