There is some evidence that mild Parkinsonian signs (MPS) are associated with increased risk of dementia, suggesting that MPS could be an early biomarker for dementia.

In a new cohort, to determine whether (1) baseline MPS are a predictor of incident dementia, (2) there is an interaction between MPS and other baseline risk factors for dementia (i.e., the presence of both together greatly elevates the risk of dementia).

In a prospective, longitudinal study of community-dwelling elders in northern Manhattan, NY, Parkinsonian signs were rated with an abbreviated Unified Parkinson’s Disease Rating Scale. Risk of incident dementia was assessed using Cox proportional hazards models.

There were 1,851 participants (mean follow-up = 3.7 years). Participants with baseline MPS were twice as likely to develop dementia as participants without MPS: 16.3% vs. 7.7%, unadjusted hazards ratio (HR)= 2.24 (p < 0.001), adjusted HR= 1.98 (p <0.001). MPS were divided into three subtypes: adjusted HR_{axial dysfunction} = 2.45 (p <0.001), adjusted HR_tremor = 2.38 (p = 0.006), and adjusted HR_rigidity = 1.16 (p = 0.58). When MPS were treated as a continuous variable, the adjusted HR = 1.15 (p = 0.001). There were no interactions between MPS and other baseline risk factors for dementia, including gender, education, race, family history of dementia, stroke, and APOE-e4.

Baseline MPS seem to be a predictor of incident dementia. These motor signs might therefore serve as a useful biomarker for emerging dementia.