title: Duration of step initiation predicts freezing in Parkinson's disease.
abstract: OBJECTIVE
  In some individuals with idiopathic Parkinson's disease (PD), freezing of gait episodes develops as the disease progresses. The neural mechanism underlying freezing in PD is poorly understood. Here, we report a 2-year follow-up on the novel discovery of prolonged step initiation duration as a potential marker of impending freezing.
  
  
  METHODS
  Non-freezing PD participants in stages 2.5-4 of the Hoehn and Yahr disease severity scale were recruited from an earlier study which determined the effect of semi-virtual cues on walking. Responders were those who completed the first step faster in the presence of the virtual cues while non-responders either did not change or took longer to complete the first step. Both groups of participants were interviewed 2 years later to determine who had developed freezing of gait.
  
  
  RESULTS
  Participants in the responder group had a 13-fold risk of developing freezing of gait within 2 years following the cueing study (OR=13.3, 95% CI=1.1-167). A cutoff score of -2.6% (i.e., a decrease in the duration of the first step with visual cues by 2.6% relative to no cues) gave a sensitivity and specificity of 100% and 89%, respectively.
  
  
  CONCLUSIONS
  To the best of our knowledge, this is the first novel discovery of a physical predictor of freezing in PD. The time to complete the first step is a simple test to administer in the clinic or at home and may therefore be easily incorporated into a fall prevention training program for PD before the inception of freezing.
authors: Department of Physical Therapy, Georgia Regents University, Augusta, GA, USA.
authors: R K
authors: RK
authors: Chong
authors: Department of Physical Therapy, Georgia Regents University, Augusta, GA, USA.
authors: K-H
authors: KH
authors: Lee
authors: Department of Neurology, Georgia Regents University, Augusta, GA, USA.
authors: J
authors: J
authors: Morgan
authors: Department of Physical Therapy, Georgia Regents University, Augusta, GA, USA.
authors: C
authors: C
authors: Wakade
mesh_terms: D000328:Adult; D000368:Aged; D018450:Disease Progression; D005260:Female; D020233:Gait Disorders, Neurologic / Q000175:diagnosis* / Q000209:etiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000150:complications*; D012680:Sensitivity and Specificity; D016138:Walking
keywords: falls; fear of falling; gait; questionnaire; walking