title: Longitudinal assessment of olfactory function in idiopathic REM sleep behavior disorder.
abstract: OBJECTIVE
  Idiopathic REM sleep behavior disorder (IRBD) is an early marker of Lewy body disorders and is linked to olfactory loss. We evaluated whether olfactory function deteriorates with time in IRBD. Progressive smell loss could be a useful way in which to monitor the effect of disease-modifying interventions in subjects with IRBD.
  
  
  METHODS
  We conducted a prospective study in which 19 IRBD patients and 19 healthy age and sex matched controls underwent serial clinical evaluations and olfactory identification testing. We used the 40-item University of Pennsylvania Smell Identification Test (UPSIT) at baseline and after 1.5, 3 and 4 years, and olfactory detection testing with the Smell Threshold Test (STT) at baseline and after 1.5 and 4 years.
  
  
  RESULTS
  Mean UPSIT score was lower (poorer smell identification) in patients than in controls at baseline, 1.5-, 3-, and 4-year assessments. Mean STT score was higher (poorer smell detection ability) in patients than in controls at 1.5- and 4-year evaluations. At 4 years, there were no differences between patients and controls in the rate of change of UPSIT (P = 0.093) and STT (P = 0.964) scores from baseline. Three patients were diagnosed with Parkinson's disease at 3-year evaluation and one with multiple system atrophy at 4-year assessment. At 4 years, UPSIT and STT scores did not change from baseline in these four patients.
  
  
  CONCLUSIONS
  In IRBD, olfactory identification and detection deficits do not worsen over time. Serial olfactory tests may not serve as an outcome measure in future disease-modifying trials in IRBD.
authors.affiliation: Neurology Service, Hospital Clinic, Barcelona, Spain. airanzo@clinic.ub.es
authors.forename: Alex
authors.initials: A
authors.lastname: Iranzo
authors.forename: Mónica
authors.initials: M
authors.lastname: Serradell
authors.forename: Isabel
authors.initials: I
authors.lastname: Vilaseca
authors.forename: Francesc
authors.initials: F
authors.lastname: Valldeoriola
authors.forename: Manel
authors.initials: M
authors.lastname: Salamero
authors.forename: Cristina
authors.initials: C
authors.lastname: Molina
authors.forename: Joan
authors.initials: J
authors.lastname: Santamaria
authors.forename: Eduardo
authors.initials: E
authors.lastname: Tolosa
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D016022:Case-Control Studies; D018450:Disease Progression; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D000857:Olfaction Disorders / Q000175:diagnosis* / Q000209:etiology*; D017286:Polysomnography; D020187:REM Sleep Behavior Disorder / Q000150:complications*; D012684:Sensory Thresholds / Q000502:physiology; D012720:Severity of Illness Index; D013997:Time Factors