title: Infections and the risk of incident giant cell arteritis: a population-based, case-control study.
abstract: OBJECTIVE
  Alterations in the immune system and infections are suspected to increase susceptibility to giant cell arteritis (GCA). Recently herpes zoster has been directly implicated in the pathogenesis of GCA. We examined the association between prior infections, in particular herpes zoster, and incident GCA in a population-based cohort.
  
  
  METHODS
  A nested case-control study was performed using an electronic database from the UK. Cases with newly diagnosed GCA were identified using a validated algorithm and compared with age-matched, sex-matched and practice-matched controls. Conditional logistic regression was used to examine the relationship between any infection or herpes zoster infection on the development of GCA after adjusting for potential confounders; results were expressed as incidence rate ratios (IRRs).
  
  
  RESULTS
  There were 4559 cases of GCA and 22 795 controls. Any prior infection and herpes zoster were associated with incident GCA (IRR 1.26 (95% CI 1.16 to 1.36), p<0.01; and 1.17 (95% CI 1.04 to 1.32), p<0.01, respectively). A greater number of infections was associated with a higher risk of developing GCA (IRR for 1, 2-4 and ≥5 infections was 1.28, 1.60 and 2.18, respectively).
  
  
  CONCLUSIONS
  Antecedent infections and, to a lesser extent, herpes zoster infections are modestly associated with incident GCA. These data provide population-level support for the hypothesis that long-standing alterations of the immune system are associated with susceptibility to GCA and suggest that herpes zoster is unlikely to play a major causal role in the pathogenesis of GCA.
authors.affiliation: Division of Rheumatology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Rennie L
authors.initials: RL
authors.lastname: Rhee
authors.affiliation: Systemic Autoimmunity Branch, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, Maryland, USA.
authors.forename: Peter C
authors.initials: PC
authors.lastname: Grayson
authors.affiliation: Division of Rheumatology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.|Department of Biostatistics and Epidemiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Merkel
authors.affiliation: Department of Public Health Sciences, University of Iceland, Reykjavik, Iceland.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Tomasson
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D005260:Female; D013700:Giant Cell Arteritis / Q000453:epidemiology* / Q000276:immunology; D005938:Glucocorticoids / Q000627:therapeutic use; D006562:Herpes Zoster / Q000453:epidemiology*; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D015994:Incidence; D007239:Infections / Q000453:epidemiology*; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D005938:Glucocorticoids; D007166:Immunosuppressive Agents
keywords: Epidemiology; Giant Cell Arteritis; Infections