New scoring system catches hidden sleep issues in Parkinson’s

A new sleep scoring system could help doctors better track sleep disruptions in people with advanced Parkinson’s disease, a study suggests.

Standard monitoring methods often miss unique disruptions in brain activity caused by the disease. By tracking five newly identified stages of abnormal sleep and wakefulness — patterns absent in healthy people and those in the early stages of the disease — researchers found that these disturbances are closely linked to older age, cognitive decline, and fluctuating motor symptoms.

“The scoring method may improve sleep assessment in neurodegenerative diseases,” the researchers wrote in the study, “Novel sleep scoring method for neurodegenerative diseases: feasibility and reliability in advanced Parkinson disease,” published in Sleep Medicine.

Sleep disturbances are a common nonmotor symptom of Parkinson’s. Sleep issues include difficulty falling or staying asleep, vivid dreams or nightmares, moving or speaking while dreaming, and excessive daytime sleepiness.

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Sleep patterns

Sleep is usually staged following the American Academy of Sleep Medicine (AASM) manual, which relies on brainwave patterns recorded by electroencephalography (EEG). Under these standard rules, a night’s sleep is divided into wakefulness, rapid eye movement (REM or dream) sleep, and three stages of non-REM sleep (N1, N2, and N3), which progress from light dozing to deep rest.

In neurodegenerative diseases like Parkinson’s, these patterns may be lost, which can compromise the accuracy of standard sleep assessments and limit the management of sleep.

Researchers in Spain and Italy previously detected five additional sleep stages in people with Parkinson’s and similar conditions: abnormal wake, subwake, undifferentiated NREM sleep, poorly structured N2 sleep, and abnormal REM sleep.

The team built on those findings, testing whether this method is feasible and reliable in Parkinson’s alone, and including more participants, a control group, and consecutive recordings from routine clinical practice.

“We selected [Parkinson’s] because it is both highly prevalent and widely recognized as a prototypical neurodegenerative disorder,” the team wrote, noting it as an “appropriate model for developing and validating the novel scoring rules in patients in whom conventional sleep stages may be absent.”

The study involved 15 adults with Parkinson’s, four of them women, and five age-matched healthy individuals (three women) who served as controls. Three patients had mild cognitive impairment and four had dementia. Motor fluctuations were seen in eight.

Each participant underwent overnight video-polysomnography, a sleep study that records brain waves, eye movements, muscle activity, breathing, and video. Five blinded scorers first assessed the recordings using AASM rules and then, where those rules could not be applied, used the new method.

The analysis detected new sleep stages in 12 (80%) of the 15 participants with Parkinson’s, accounting for a median of 56.8% of recording time.

All 12 patients (100%) had undifferentiated NREM light and deep sleep, while subwake was found in nine (75%) and abnormal wake in seven (58.3%). Slow arousals, encapsulated REM sleep behavior disorder (brief, REM-like episodes occurring within non-REM sleep), and abnormal REM sleep were each detected in seven (58.3%). Poorly structured N2 sleep was not observed.

The three remaining participants in the early stages of disease, who had neither cognitive impairment nor motor fluctuations, had recordings that could be scored entirely with AASM criteria. No abnormal stages were seen in any of the healthy control participants.

When the researchers compared clinical data with the novel stages, older age at the time of the study was linked with abnormal wake, slow arousals, and abnormal REM sleep. Cognitive impairment was associated with abnormal wake, slow arousals, encapsulated episodes of REM sleep behavior disorder, and abnormal REM sleep. The undifferentiated NREM stage was associated with motor fluctuations.

To assess the reliability of the new system, five specialists with varying levels of experience — two neurologists and three sleep technicians — independently scored the sleep recordings. Overall, they agreed just as consistently using the new method as they did with the standard system.

While scoring healthy individuals produced nearly perfect agreement, evaluating patients with Parkinson’s proved more challenging. Scorers showed the strongest consensus on clear-cut stages such as wakefulness, deep sleep, and REM sleep, as well as on the novel undifferentiated non-REM stages. Transitional stages, such as light sleep (N1) and subwake, were harder to pin down, though the new method still captured light sleep better than the standard method did.

Using the novel method, scorers had a harder time reaching agreement in patients who were older than 75 or living with dementia, whose sleep patterns were the most severely disrupted. With the AASM method, agreement was also significantly lower in patients with dementia, while age showed no relationship.

The team concluded that the proposed method is “feasible, reliable, and clinically applicable in advanced Parkinson disease,” and that it will help identify “abnormal sleep-wake stages that are not captured by conventional AASM criteria.”