In a new study researchers have found a set of nonmotor and nondopaminergic motor features that predict dementia in patients with Parkinson’s disease (PD). These include orthostatic hypotension, impaired color vision and REM sleep behavior disorder (RBD), according to Ronald Postuma, McGill University, Montreal, Quebec, Canada, and study co-authors.
These findings were the result of a 4.4-year follow-up of 80 PD patients. Researchers used a battery of tests of executive function, memory and visuospatial ability to identify 27 of the patients who developed dementia. An especially strong predictor was orthostatic hypotension with each 10 mmHg drop in systolic blood pressure associated with a 1.84-fold increased likelihood of developing dementia and anything greater than 10 mmHg had a 7.30-fold increased risk.
“The mechanism for this striking relationship is unclear”, write the researchers. In addition, RBD was also a strong predictor. Nearly 96 percent of the patients who developed dementia had RBD at baseline, showing there was nearly a 50-fold increased risk associated with RBD. “It is unclear why this very strong relationship should exist”, say Postuma.
Having impaired vision was associated with a threefold increased dementia risk, having mild cognitive impairment at baseline was a strong predictor, and patients with gait were predictors of developing dementia. “Of importance, gait and postural disturbance are part of the classification of akinetic-rigid vs tremor-predominant disease”, say the researchers, adding that “our study suggests that it may be the gait component of this classification that is the primary driver of dementia risk.”