Current knowledge about the rate of progression of extrapyramidal signs (EPSs) in Parkinson disease (PD) is derived largely from cross-sectional studies comparing subjects at various stages of illness rather than longitudinal studies in which the subjects were followed up over time.
To longitudinally study the progression of EPSs in PD by quantifying the rate of change of EPSs and by examining each EPS (rigidity, bradykinesia, tremor, and postural instability) separately.
A community-based cohort of 237 patients with PD living in Washington Heights–Inwood in Manhattan, NY, was evaluated at baseline and at yearly intervals. The EPSs were rated using the motor portion of the Unified Parkinson's Disease Rating Scale Motor Examination. Analyses of longitudinal data were performed by applying generalized estimating equations to regression analyses.
The total EPS score increased at an annual rate of 1.5 points (1.5%), but, among those who died, the total EPS score increased at an annual rate of 3.6 points (3.6%). Bradykinesia, rigidity, and gait and balance subscores worsened at similar annual rates of 2.0% to 3.1%, whereas the tremor subscore did not clearly worsen with time. Patients with a shorter disease duration (≤3 years) may have progressed more rapidly than patients with longer disease duration (annual rate of change, 1.9% vs 1.4%, respectively), although this did not reach statistical significance. A high total EPS score was independently associated with dementia, low Activities of Daily Living score, and long disease duration at baseline.
In this cohort, the progression of EPSs in PD occurred at a rate of 1.5% per year and at twice that rate among those who died. Bradykinesia, rigidity, and gait and balance impairment worsened at similar rates, whereas tremor did not, suggesting that tremor may be relatively independent of these other cardinal manifestations of PD.