title: The Insomnia Severity Index: cross-cultural adaptation and psychometric evaluation of a Persian version.
abstract: OBJECTIVE
  The main purpose of this study was to describe the cultural adaptation of a Persian version of the Insomnia Severity Index and to evaluate its psychometric properties by testing internal consistency, construct validity, discriminant validity, and concurrent validity.
  
  
  METHODS
  Cross-cultural adaptation was carried out according to guidelines and included forward and backward translations, expert committee, and field test. A sample of 1,037 sleep clinic patients filled in a questionnaire package including the Persian version of the Insomnia Severity Index (ISI-P), the Pittsburgh Sleep Quality Index (PSQI), the Epworth Sleepiness Scale (ESS), and the Beck Depression Inventory (BDI). In addition, 624 of these patients were assessed by polysomnography (PSG). A group of 50 members of hospital staff responded to the ISI-P as the control group. Internal consistency with Cronbach's alpha, construct validity with principal component analysis, discriminant validity with assessing the ISI-P's ability to differentiate patients from control group and concurrent validity with exploring the spearman correlation with the PSQI, ESS, BDI, and corresponding parameters in PSG were followed to examine the psychometric properties of the ISI-P.
  
  
  RESULTS
  The ISI-P showed acceptable internal consistency (Cronbach's alpha = 0.78) and a 2-factor solution in factor analysis. The ISI-P discriminated well between patients and control group (15.90 ± 6.12 vs 10.10 ± 5.76, P value <0.001). Items and total score of the ISI-P showed a weak correlation with the corresponding parameters in PSG. The ISI-P total score was significantly correlated with total score of the PSQI (r = 0.74, P value <0.001) and the BDI (r = 0.42, P value <0.001), while it was not significantly correlated with total score of the ESS (r = 0.12, P value = 0.72).
  
  
  CONCLUSIONS
  Cross-cultural adaptation was successful, and the ISI-P has good psychometric properties. Using the ISI-P is recommended to evaluate insomnia in research and clinical settings in Persian-speaking people.
authors.affiliation: Occupational Sleep Research Center, Tehran University of Medical Sciences, Tehran, Iran.
authors.forename: Khosro
authors.initials: K
authors.lastname: Sadeghniiat-Haghighi
authors.forename: Ali
authors.initials: A
authors.lastname: Montazeri
authors.forename: Ahmad
authors.initials: A
authors.lastname: Khajeh-Mehrizi
authors.forename: Saharnaz
authors.initials: S
authors.lastname: Nedjat
authors.forename: Omid
authors.initials: O
authors.lastname: Aminian
mesh_terms: D000328:Adult; D003431:Cross-Cultural Comparison; D005260:Female; D006801:Humans; D007492:Iran; D008297:Male; D008875:Middle Aged; D010555:Personality Inventory; D017286:Polysomnography; D011594:Psychometrics / Q000379:methods*; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D007319:Sleep Initiation and Maintenance Disorders / Q000175:diagnosis* / Q000523:psychology*; D011795:Surveys and Questionnaires; D014177:Translations
references.citation: Arch Gen Psychiatry. 1961 Jun;4:561-71
references.pmid: 13688369
references.citation: Psychooncology. 2005 Jun;14(6):429-41
references.pmid: 15376284
references.citation: Psychiatry Res. 1989 May;28(2):193-213
references.pmid: 2748771
references.citation: Sleep Med. 2012 Feb;13(2):207-10
references.pmid: 22172961
references.citation: Depress Anxiety. 2005;21(4):185-92
references.pmid: 16075452
references.citation: Spine (Phila Pa 1976). 2000 Dec 15;25(24):3186-91
references.pmid: 11124735
references.citation: J Psychosom Res. 1999 Oct;47(4):335-41
references.pmid: 10616227
references.citation: Sleep Breath. 2013 Mar;17(1):419-26
references.pmid: 22327509
references.citation: Arch Gen Psychiatry. 1985 Mar;42(3):225-32
references.pmid: 2858188
references.citation: Sleep Med. 2001 Jul;2(4):297-307
references.pmid: 11438246
references.citation: Sleep. 1991 Dec;14(6):540-5
references.pmid: 1798888
references.citation: Sleep Breath. 2012 Mar;16(1):79-82
references.pmid: 21614577
references.citation: J Adv Nurs. 2010 Oct;66(10):2350-9
references.pmid: 20722803
references.citation: Sleep. 2011 May 01;34(5):601-8
references.pmid: 21532953
references.citation: Sleep. 1995 Jan;18(1):58-70
references.pmid: 7761745
references.citation: Sleep. 2000 Mar 15;23(2):205-12
references.pmid: 10737337
references.citation: Am J Psychiatry. 1993 Jun;150(6):867-72
references.pmid: 8494060
references.citation: Sleep. 1997 Jun;20(6):406-22
references.pmid: 9302725
references.citation: Sleep Med. 2011 May;12(5):463-70
references.pmid: 21493134