title: Effect of diabetes mellitus on giant cell arteritis.
abstract: BACKGROUND
  To determine if Type 2 diabetes mellitus (DM) is protective against giant cell arteritis (GCA) and to estimate the incidence of GCA diagnosis from Medicare claims.
  
  
  METHODS
  Medicare 5% claims files from 1991 to 2011 were used to identify beneficiaries diagnosed with DM, but not GCA, within a 3-year ascertainment period. Propensity score matching was used to define a control group of nondiabetics with comparable demographic covariates. Competing risk regression was then used to assess the impact of DM diagnosis on GCA diagnosis. To allow for a 3-year ascertainment period, the analysis sample was limited to beneficiaries older than 68 years at baseline.
  
  
  RESULTS
  A total of 151,041 beneficiaries diagnosed with DM were matched to an equal number of controls. Mean study follow-up was 67.75 months. GCA was diagnosed among 1116 beneficiaries with DM (0.73%) vs 465 (0.30%) controls. The risk of receiving a GCA diagnosis among patients with DM was increased by 100% (subhazard ratio, 2.00; 95% confidence interval, 1.78-2.25). The annual incidence of GCA diagnosis among claims for US Medicare beneficiaries older than 68 years old was 93 in 100,000.
  
  
  CONCLUSIONS
  A DM diagnosis is not protective against a GCA diagnosis in the Medicare population. Our data suggest that a DM diagnosis increases the risk of GCA diagnosis within 5.7 years for Medicare beneficiaries older than 68 years.
authors.affiliation: Departments of Ophthalmology and Visual Neurosciences (ASA, MSL), Neurology (MSL), and Neurosurgery (MSL), University of Minnesota, Minneapolis, Minnesota; and Department of Economics (APY, FAS), Duke University, Durham, North Carolina.
authors.forename: Anne S
authors.initials: AS
authors.lastname: Abel
authors.forename: Arseniy P
authors.initials: AP
authors.lastname: Yashkin
authors.forename: Frank A
authors.initials: FA
authors.lastname: Sloan
authors.forename: Michael S
authors.initials: MS
authors.lastname: Lee
mesh_terms: D003920:Diabetes Mellitus / Q000175:diagnosis / Q000453:epidemiology*; D005260:Female; D013700:Giant Cell Arteritis / Q000175:diagnosis / Q000453:epidemiology*; D006801:Humans; D008297:Male; D006278:Medicare / Q000706:statistics & numerical data; D012189:Retrospective Studies; D014481:United States / Q000453:epidemiology