Sleep disorder linked to poor nonmotor status in Parkinson’s disease

By Eleanor McDermid, Senior medwireNews Reporter

The presence of rapid eye movement sleep behavior disorder (RBD) is associated with more severe nonmotor symptoms in patients with early-stage Parkinson’s disease (PD), a study shows.

In addition to worse nonmotor symptoms, patients with the comorbidity had a poorer subjective view of their motor functioning, despite having similar objective motor function to those without RBD. They also reported a worse quality of life.

Michele Hu (Oxford Parkinson’s Disease Centre, UK) and co-workers found the same differences after excluding patients in whom RBD was likely secondary to medication use, suggesting that the differences were probably caused by the underlying pathology.

“These findings go some way to support previous theories that RBD marks a more diffuse and complex phenotype of PD,” they write in the Journal of Neurology, Neurosurgery, and Psychiatry.

“However, we cannot specify whether it is the [probable] RBD itself that is responsible for this phenotype or whether this is due to an association with other non-motor symptoms, for example, a greater prevalence of depression or cognitive impairment.”

Of 475 patients with PD diagnosed within the previous 3.5 years, 224 had probable RBD, based on their responses to the REM Sleep Behavior Disorder Screening Questionnaire.

These patients were significantly more likely than those without RBD to endorse most items on part I of the Unified PD Rating Scale (UPDRS). For example, 19.2% versus 8.8% reported hallucinations, and 58.8% versus 40.7% reported constipation. They also had more depressive symptoms and more severe orthostatic hypotension.

In addition, patients with comorbid RBD had slightly but significantly lower scores on the Mini-Mental State Examination, at 27.1 versus 27.5. The researchers note that this difference was “modest,” and that there was no significant difference in Montreal Cognitive Assessment scores, but add that far more patients with than without RBD reached the threshold for cognitive impairment, at 56.7% versus 14.9%.

Patients with comorbid RBD had similar objective motor function to those without, with UPDRS-III scores of 26.8 and 26.9, respectively, and performed equally well in the Purdue Pegboard and Timed Up and Go tests. Yet they had a poorer subjective view of their motor function as assessed on the UPDRS part II, being significantly more likely to report problems with speech, chewing and swallowing, turning in bed, walking and balance, and freezing.

This was reflected in patients’ quality of life; they had an overall score of 66.4 on the EQ-5D compared with 71.9 for patients without RBD, and the difference was apparent in all EQ-5D domains.

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