Three Nonmotor Symptoms Found to Be Key Predictors of Poor Parkinson’s Response

To define Parkinson’s disease as a motor disorder would be accurate, but it does not tell the whole story of a condition that can present a range of psychiatric, cognitive, and physiologic symptoms.

In recent years these nonmotor symptoms have taken on increased importance. While historically people with Parkinson’s were distinguished based on the age of disease onset and degree of their tremors, evidence is growing that nonmotor symptoms determine the severity of the disease and how it will progress.

Researchers from Montreal and Stockholm have now identified three particular symptoms—mild cognitive impairment (MCI), REM sleep behavior disorder (RBD, bodily movements during dreaming), and orthostatic hypotension—that can strongly predict how Parkinson’s will progress in someone.

Their findings were published online in JAMA Neurology on June 15.

“A real strength of this work is the extensive battery of motor and nonmotor tests the researchers administered to identify these determinants,” said Daniel Weintraub, M.D., an associate professor of psychiatry at the University of Pennsylvania.

The researchers performed 34 assessments on each participant in the group—which consisted of 73 male and 40 female patients with Parkinson’s—at the start of the study, and then again a few years later. They then analyzed the various patient characteristics to see which cluster of traits correlated best with a more rapid progression of their disease.

They first identified seven characteristics that were telling: orthostatic hypotension, MCI, RBD, depression, anxiety, and scores on the unified Parkinson’s disease rating scale (UPDRS) parts II (self-evaluation of daily life) and III (motor evaluation by clinician).

They eventually narrowed it down to those first three symptoms, which divided the study participants into three clinical Parkinson’s subtypes: mainly motor, intermediate, or diffuse.

The people in the diffuse group had the highest occurrences of these conditions (of the 40 patients in this group, all of them had MCI and orthostatic hypotension, and 37 had RBD); correspondingly, they had the worst disease progression over the years. The mainly motor group fared best, and the intermediate group fell in between, though closer to the mainly motor side.

Lead author Ronald Postuma, M.D., a professor of medicine in the Department of Neurology and Neurosurgery at McGill University, was not certain what underlying mechanism might link these symptoms, as they are biologically quite diverse (which is why the group was classified as diffuse).

“Still, these results provide compelling evidence that doctors should screen Parkinson’s patients for these three symptoms at baseline visits,” he said.

He also added that the average age and Parkinson’s duration were similar across the three groups, so the diffuse group was not simply representative of a more advanced disease stage.

Weintraub agreed that this work provides another illustration of the high degree of problems with which people with Parkinson’s have to deal. “But it would be useful to see a study like this replicated in a larger and more typical Parkinson’s population,” he told Psychiatric News. “Over half the participants had cognitive impairment at the start of the study, which is higher than average.”

This study was supported by the Fonds de Recherche du Quȳbec-Santȳ and the Canadian Institute of Health Research. ■