title: Allergy immunotherapy for allergic rhinitis effectively prevents asthma: Results from a large retrospective cohort study.
abstract: BACKGROUND
  Allergic rhinitis (AR) is a main risk factor for the development of asthma. Two randomized open-label trials indicated that allergy immunotherapy (AIT) prevents the onset of asthma in patients with AR. However, these trials have methodological limitations, and it is unclear to what extent this experimental efficacy translates into clinical effectiveness.
  
  
  OBJECTIVE
  We sought to investigate the effectiveness of AIT to prevent asthma in patients with AR.
  
  
  METHODS
  Using routine health care data from German National Health Insurance beneficiaries, we identified a consecutive cohort of 118,754 patients with AR but without asthma who had not received AIT in 2005. These patients were stratified into one group starting AIT in 2006 and one group receiving no AIT in 2006. Both groups were observed regarding the risk of incident asthma in 2007 to 2012. Risk ratios (RRs) were calculated with generalized linear models by using a Poisson link function with robust error variance and adjustment for age, sex, health care use because of AR, and use of antihistamines.
  
  
  RESULTS
  In a total of 2431 (2.0%) patients, AIT was started in 2006. Asthma was newly diagnosed from 2007-2012 in 1646 (1.4%) patients. The risk of incident asthma was significantly lower in patients exposed to AIT (RR, 0.60; 95% CI, 0.42-0.84) compared with patients receiving no AIT in 2006. Sensitivity analyses suggested significant preventive effects of subcutaneous immunotherapy (RR, 0.54; 95% CI, 0.38-0.84) and AIT including native (nonallergoid) allergens (RR, 0.22; 95% CI, 0.02-0.68). AIT for 3 or more years tended to have stronger preventive effects than AIT for less than 3 years.
  
  
  CONCLUSIONS
  AIT effectively prevents asthma in patients with AR in a real-world setting. Confounding by indication cannot be excluded but would lead to an underestimation of the true preventive effects of AIT.
authors.affiliation: Center for Evidence-based Healthcare, Medical Faculty Carl Gustav Carus, TU Dresden, Dresden, Germany. Electronic address: jochen.schmitt@uniklinikum-dresden.de.
authors.forename: Jochen
authors.initials: J
authors.lastname: Schmitt
authors.affiliation: Center for Evidence-based Healthcare, Medical Faculty Carl Gustav Carus, TU Dresden, Dresden, Germany.
authors.forename: Kristin
authors.initials: K
authors.lastname: Schwarz
authors.affiliation: Center for Evidence-based Healthcare, Medical Faculty Carl Gustav Carus, TU Dresden, Dresden, Germany.
authors.forename: Erich
authors.initials: E
authors.lastname: Stadler
authors.affiliation: Department for Otorhinolaryngology, Medical Faculty Carl Gustav Carus, TU Dresden, Dresden, Germany.
authors.forename: Eike Gunther
authors.initials: EG
authors.lastname: Wüstenberg
mesh_terms: D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000453:epidemiology / Q000517:prevention & control*; D002648:Child; D003888:Desensitization, Immunologic; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D065631:Rhinitis, Allergic / Q000453:epidemiology / Q000628:therapy*; D012306:Risk; D055815:Young Adult
keywords: Allergic rhinitis; allergy immunotherapy; asthma; cohort study; effectiveness; epidemiology; prevention