title: Geriatric Anxiety Scale: item response theory analysis, differential item functioning, and creation of a ten-item short form (GAS-10).
abstract: BACKGROUND
  The Geriatric Anxiety Scale (GAS; Segal et al. (Segal, D. L., June, A., Payne, M., Coolidge, F. L. and Yochim, B. (2010). Journal of Anxiety Disorders, 24, 709-714. doi:10.1016/j.janxdis.2010.05.002) is a self-report measure of anxiety that was designed to address unique issues associated with anxiety assessment in older adults. This study is the first to use item response theory (IRT) to examine the psychometric properties of a measure of anxiety in older adults.
  
  
  METHODS
  A large sample of older adults (n = 581; mean age = 72.32 years, SD = 7.64 years, range = 60 to 96 years; 64% women; 88% European American) completed the GAS. IRT properties were examined. The presence of differential item functioning (DIF) or measurement bias by age and sex was assessed, and a ten-item short form of the GAS (called the GAS-10) was created.
  
  
  RESULTS
  All GAS items had discrimination parameters of 1.07 or greater. Items from the somatic subscale tended to have lower discrimination parameters than items on the cognitive or affective subscales. Two items were flagged for DIF, but the impact of the DIF was negligible. Women scored significantly higher than men on the GAS and its subscales. Participants in the young-old group (60 to 79 years old) scored significantly higher on the cognitive subscale than participants in the old-old group (80 years old and older).
  
  
  CONCLUSIONS
  Results from the IRT analyses indicated that the GAS and GAS-10 have strong psychometric properties among older adults. We conclude by discussing implications and future research directions.
authors.affiliation: Veterans Affairs Puget Sound Health Care System,American Lake Division,Washington,USA.
authors.forename: Anne E
authors.initials: AE
authors.lastname: Mueller
authors.affiliation: Department of Psychology,University of Colorado at Colorado Springs,Colorado,USA.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Segal
authors.affiliation: Department of Psychology,University of Colorado at Colorado Springs,Colorado,USA.
authors.forename: Brandon
authors.initials: B
authors.lastname: Gavett
authors.affiliation: Transitions Professional Center,Portland,Oregon,USA.
authors.forename: Meghan A
authors.initials: MA
authors.lastname: Marty
authors.affiliation: Department of Psychology,University of Colorado at Colorado Springs,Colorado,USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Yochim
authors.affiliation: Department of Psychological Science,Central Connecticut State University,New Britain,Connecticut,USA.
authors.forename: Andrea
authors.initials: A
authors.lastname: June
authors.affiliation: Department of Psychology,University of Colorado at Colorado Springs,Colorado,USA.
authors.forename: Frederick L
authors.initials: FL
authors.lastname: Coolidge
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001007:Anxiety / Q000175:diagnosis* / Q000453:epidemiology*; D015982:Bias; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011569:Psychiatric Status Rating Scales / Q000592:standards*; D011594:Psychometrics; D015203:Reproducibility of Results; D057566:Self Report; D012737:Sex Factors
keywords: anxiety; anxiety assessment; geriatric; item response theory; short form