Sleep Problems in Parkinson’s May Be Linked to Certain Medications
Dopaminergic medications could promote waking from sleep, researchers say
Sleep disturbances are common in people with diseases marked by alpha-synuclein buildup, but they are especially problematic among Parkinson’s disease patients on dopaminergic medications, a study suggests.
Parkinson’s patients tend to have more arousals during sleep and fewer normal sleep cycles than people with isolated rapid eye movement (REM) sleep behavior disorder or dementia with Lewy Bodies (DLB), data show. However, these differences were no longer significant when accounting for the potential influence of medications.
Parkinson’s disease and DLB are often considered to lie on the same continuum of disorders marked by toxic buildup of the alpha-synuclein protein in the brain. While they share common symptoms, including movement and cognitive impairments, cognitive problems tend to develop more quickly in DLB.
Both conditions are marked by sleep disruptions, including REM sleep behavior disorder (RBD).
What happens during a typical sleep cycle?
A normal sleep cycle occurs in five stages: wake, three stages of non-REM sleep, and REM sleep. These cycles repeat themselves, becoming progressively shorter through the night.
During the REM phase, the brain is active and dreams are vivid. To prevent the body from moving too much when a person is dreaming, changes in brain signaling cause muscles to become “paralyzed.” However, this doesn’t happen in RBD, leading to excessive body movements in response to dreams.
When RBD emerges before evidence of the motor and cognitive symptoms used to diagnose these neurodegenerative diseases, it is called isolated RBD, or iRBD, which has also been associated with early alpha-synuclein buildup.
“Thus, [Parkinson’s], DLB, and iRBD could be considered different stages of the same neuropathological process,” the researchers wrote, with iRBD representing an early phase of alpha-synuclein accumulation and DLB the most advanced.
While REM sleep has been the focus of much sleep research in these conditions, it is not well-established how other components of sleep might be affected in each of these three disease states.
Therefore, a pair of researchers in Portugal set out to evaluate various components of sleep — measured by polysomnography — between individuals with iRDB, DLB, and Parkinson’s who underwent a sleep evaluation at a center in Lisbon, Portugal, between January 2015 and June 2021.
The analysis included 54 individuals with Parkinson’s (21 with RBD), 24 with DLB (12 with RBD), and 21 with iRBD. Various facets of sleep were compared between each of the three groups, but also more broadly between patients who had RBD and those who didn’t.
In general, iRBD patients were more frequently male than in the other two groups, and DLB patients were significantly older. Parkinson’s patients more often used dopaminergic medications — a common class of treatments for the disease — whereas DLB patients used more acetylcholinesterase inhibitors.
Overall sleep stability and transitions between sleep phases did not differ by disease type.
“This suggests that the three different disorders are equally affected by changes in the flip-flop mechanism involved in maintaining and switching between states of consciousness,” the researchers wrote, suggesting that the brain regions involved in sleep stability are affected early in disease, and not added to with disease progression.
Data did show, however, that the number of arousals during non-REM sleep were significantly greater among Parkinson’s patients than iRBD patients. That association was lost when accounting for medication use in the statistical analyses.
This finding suggests that the use of dopaminergic medications, which was more prevalent among Parkinson’s patients, could promote waking from sleep.
All three groups showed a low number of sleep cycles through the night compared with the 4–6 typically seen in the general population during an eight-hour sleep period. The mean number of cycles was 2.9 among iRBD patients, 2.25 in DLB, and 1.39 in Parkinson’s.
About a quarter of participants (24%) had no sleep cycle, mostly due to a lack of REM sleep entirely in some Parkinson’s and DLB patients.
The lower number of cycles among Parkinson’s patients relative to the other two groups could be associated with medication use. Again, the differences between groups were lost when medications were accounted for in the analyses.
A greater degree of motor dysfunction in Parkinson’s patients might also play a role, although this was not measured in the study, the team noted.
No sleep measurements differed significantly when comparisons were made between patients with or without RBD regardless of disease type, “which suggests that disease differences could play a larger role in arousals and sleep cycle duration changes than the presence of RBD,” the researchers wrote.
That hypothesis would “merit confirmation from larger sample studies and comparison with a non-neurological control group,” the team concluded.