title: Fatigue and daytime sleepiness scale in myotonic dystrophy type 1.
abstract: BACKGROUND
  Fatigue and excessive daytime sleepiness are frequent complaints in myotonic dystrophy type 1 (DM1) that often overlap. We aimed to construct a combined fatigue and daytime sleepiness rating scale for DM1 using the Rasch measurement model.
  
  
  METHODS
  Questionnaires, including the Epworth sleepiness scale, fatigue severity scale, and daytime sleepiness scale, were completed by 354 patients. Data were subjected to Rasch analyses and tested for required measurement issues such as appropriate response categories, absence of item bias, local independence, and unidimensionality.
  
  
  RESULTS
  The initial 22 items did not meet Rasch model expectations. After rescoring and removing misfitting items, the final 12-item scale showed good model fit and unidimensionality. High internal consistency (person separation index = 0.80) and validity were demonstrated.
  
  
  CONCLUSIONS
  The Rasch-built Fatigue and Daytime Sleepiness Scale, developed specifically for DM1 patients, provides interval measures on a single continuum. Its use is suggested for future clinical trials and therapeutic follow-up.
authors.affiliation: Department of Neurology, Maastricht University Medical Centre P.O. Box 5800, 6202 AZ, Maastricht, The Netherlands. m.hermans@mumc.nl
authors.forename: Mieke C E
authors.initials: MC
authors.lastname: Hermans
authors.forename: Ingemar S J
authors.initials: IS
authors.lastname: Merkies
authors.forename: Luc
authors.initials: L
authors.lastname: Laberge
authors.forename: Eveline W
authors.initials: EW
authors.lastname: Blom
authors.forename: Alan
authors.initials: A
authors.lastname: Tennant
authors.forename: Catharina G
authors.initials: CG
authors.lastname: Faber
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005221:Fatigue / Q000150:complications / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009223:Myotonic Dystrophy / Q000150:complications / Q000503:physiopathology*; D012720:Severity of Illness Index; D012890:Sleep / Q000502:physiology*; D011795:Surveys and Questionnaires; D063189:Symptom Assessment / Q000379:methods*