title: Measurement properties of the minimal insomnia symptom scale as an insomnia screening tool for adults and the elderly.
abstract: BACKGROUND
  The psychometric properties of the three-item Minimal Insomnia Symptom Scale (MISS) were evaluated using the classical test theory. Different cut-offs for identifying insomnia were suggested in two age groups (≥6 and ≥7 among adult and elderly people, respectively). The aim of the present study was to test the measurement properties of the MISS using the Rasch measurement model, with special emphasis on differential item functioning by gender and age.
  
  
  METHODS
  Cross-sectional MISS data from adult (age 20-64 years, n = 1075) and elderly (age 65+, n = 548) populations were analysed using the Rasch measurement model.
  
  
  RESULTS
  Data generally met Rasch model requirements and the scale could separate between two distinct groups of people. Differential item functioning was found by age but not gender. The difference between the adult and elderly samples was lower for the originally recommended ≥6 points cut-off (0.09 logits) than for the ≥7 points cut-off (0.23 logits), but greater at the lower and higher ends of the scale.
  
  
  CONCLUSIONS
  This study provides general support for the measurement properties of the MISS. Caution should be exercised in comparing raw MISS scores between age groups, but applying a ≥6 cut-off appears to allow for valid comparisons between adults and the elderly regarding the presence of insomnia. Nevertheless, additional studies are needed to determine the clinically optimal cut-score for identification of insomnia.
authors: The PRO-CARE Group, School of Health and Society, Kristianstad University, Kristianstad, Sweden. Electronic address: Albert.Westergren@hkr.se.
authors: Albert
authors: A
authors: Westergren
authors: Department of Neuroscience, Psychiatry, Uppsala University, Uppsala, Sweden.
authors: Jan-Erik
authors: JE
authors: Broman
authors: Department of Health, Blekinge Institute of Technology, Karlskrona, Sweden; Department of Health and Caring Sciences, Linnæus University, Kalmar, Sweden.
authors: Amanda
authors: A
authors: Hellström
authors: Department of Health, Blekinge Institute of Technology, Karlskrona, Sweden.
authors: Cecilia
authors: C
authors: Fagerström
authors: Department of Health, Blekinge Institute of Technology, Karlskrona, Sweden; The Department of Care Science, Faculty of Health and Society, Malmö University, Malmö, Sweden.
authors: Ania
authors: A
authors: Willman
authors: The PRO-CARE Group, School of Health and Society, Kristianstad University, Kristianstad, Sweden.
authors: Peter
authors: P
authors: Hagell
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D011594:Psychometrics; D015203:Reproducibility of Results; D012737:Sex Factors; D007319:Sleep Initiation and Maintenance Disorders / Q000150:complications* / Q000175:diagnosis / Q000523:psychology*; D011795:Surveys and Questionnaires; D013548:Sweden; D063189:Symptom Assessment; D055815:Young Adult
keywords: Clinical insomnia; Invariant comparisons; MISS; Psychometric properties; Reliability; Targeting