Motor impairment in PD - Relationship to incident dementia and age

Objective: To analyze the relationship of specific motor impairment in idio pathic PD to incident dementia. Background: The total Unified PD Rating Sca le (UPDRS) motor score at baseline has been associated with an increased ri sk of developing dementia in PD. Methods: A cohort of 214 nondemented commu nity-dwelling patients with PD was followed annually with neurologic and ne uropsychological evaluations. The association of baseline motor impairment with incident dementia was analyzed using Cox proportional hazards models. Facial expression, tremor, rigidity, and bradykinesia were analyzed as part of subscore A (indicative of dopaminergic deficiency); speech and axial im pairment were analyzed as part of subscore B (indicative of predominantly n ondopaminergic deficiency). The correlation between the six motor domains a nd age was also analyzed. Results: Of 173 patients followed for at least 1 year, 50 became demented according to the Diagnostic and Statistical Manual of Mental Disorders, revised 3rd edition (DSM III-R) criteria (mean follow -up, 3.6 +/- 2.2 years). When both subscores A and B were entered into the Cox model, subscore B was associated with incident dementia (relative risk = 1.19; 95% CI, 1.09 to 1.30; p = 0.0001), in addition to gender, age, and education, whereas subscore A was not (relative risk = 1.03; 95% CI, 0.99 t o 1.07; p = 0.19). Of the six motor domains, speech and bradykinesia were a ssociated with incident dementia (p < 0.05), and axial impairment approache d significance (p = 0.06). Only axial impairment was correlated with age (c orrelation coefficient = 0.32; p < 0.001). Conclusion: The findings suggest that motor impairment mediated predominantly by nondopaminergic systems is associated with incident dementia in PD. Axial impairment may be the resul t of a combined effect of the disease and the aging process.