Association between presenting motor symptoms and the risk of cognitive impairment in Parkinson's disease

Neuropsychological data collected from two groups of patients with idiopathic Parkinson's disease (n = 50, 159) were analysed to investigate the association between presenting motor symptoms determined from retrospective chart review and the risk of cognitive impairment. Presenting motor symptoms were abstracted from the medical records and coded by type, location, and laterality. Longitudinal data on changes in the maximum speed of voluntary arm movements were available for a subsample of patients. Bilateral (v unilateral) presentation was associated with an increased risk of cognitive impairment an average of nine years after onset of disease as measured by memory tests and the mini-mental state examination. A higher rate of decline of arm movement speed was also predictive of greater memory dysfunction. The type, side (left v right), and location (lower v upper extremity) of the presenting symptoms were not, however, consistently associated with the risk of cognitive impairment later in the course of the disease.