Longitudinal assessment of olfactory function in idiopathic REM sleep behavior disorder

Parkinsonism Relat Disord. 2013 Jun;19(6):600-4. doi: 10.1016/j.parkreldis.2013.02.009. Epub 2013 Mar 23.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Analysis of Variance
  • Case-Control Studies
  • Disease Progression
  • Female
  • Humans
  • Longitudinal Studies
  • Male
  • Middle Aged
  • Olfaction Disorders / diagnosis*
  • Olfaction Disorders / etiology*
  • Polysomnography
  • REM Sleep Behavior Disorder / complications*
  • Sensory Thresholds / physiology
  • Severity of Illness Index
  • Time Factors