Sweet or Bland Dreams? Taste Loss in Isolated REM-Sleep Behavior Disorder and Parkinson's Disease.

Background: Hyposmia and isolated REM sleep behavior disorder are well-established features of prodromal Parkinson's disease (PD).

Objectives: The objective of the present study was to evaluate whether taste loss (reported in PD and possibly suggesting brain stem involvement) is present at the isolated REM sleep behavior disorder stage.

Methods: We assessed taste function using the Taste Strip Test (evaluating 4 concentrations of bitter, sweet, sour, and salty) in 44 participants with isolated REM sleep behavior disorder, 19 with PD, and 29 controls.