Inflammatory Markers, Sleep Disorder Linked In Parkinson’s
Blood levels of c-reactive protein (CRP) and the lymphocyte-to-monocyte ratio (LMR), two indicators of systemic inflammation, were associated with the presence of rapid eye movement (REM) sleep behavior disorder (RBD) in people with Parkinson’s disease, a study found.
Patients with RBD also had worse cognition than those who did not.
The findings suggest that “inflammatory factors are associated with the pathogenesis of RBD in [Parkinson’s] patients,” the researchers wrote, noting that they could serve as potential RBD biomarkers in Parkinson’s.
“However, the role of peripheral [outside the brain and spinal cord] inflammation in disease progression still needs to be elucidated in a larger sample size,” they said.
During the REM phase of sleep, the brain is very active and dreams are particularly vivid. Normally, changes in brain signaling cause the muscles to lose tone, “paralyzing” the body and preventing it from moving too much in response to dreams.
RBD is a common non-motor symptom of Parkinson’s wherein this paralysis does not occur, leading to violent and complex movements while dreaming. Such movements can lead to serious injury to the person or those near them during sleep.
Recent research suggests that inflammation may play a role in causing RBD, but the mechanisms through which it does so are not clear.
A research team in China examined the potential association by measuring blood levels of inflammatory markers in Parkinson’s patients with or without RBD, and a group of healthy volunteers.
A total of 153 patients were enrolled; 60 had RBD and 93 did not. An additional 36 healthy people were also enrolled.
In general, baseline characteristics did not differ between the two patient groups. Motor symptoms, general sleepiness, and medication doses were comparable. But levels of inflammatory markers were different.
In particular, patients with RBD had higher levels of CRP, a biomarker of acute inflammation. They also had increased levels of monocytes — an immune cell type previously associated with non-motor Parkinson’s symptoms — and decreased levels of lymphocytes, a family of infection-fighting white blood cells.
Those with RBD had a higher neutrophil-to-lymphocyte ratio, and a lower lymphocyte-to-monocyte ratio (LMR), both of which are indicators of systemic inflammation.
An analysis also showed that levels of CRP and the LMR were significant predictive factors of RBD, with increased CRP being a risk factor and a higher LMR ratio being a protective factor. Both have been previously associated with Parkinson’s, the researchers noted.
Blood CRP concentrations over 5.05 mg/mL were predictive of RBD, and an LMR of 4.125 was also predictive, according to the researchers.
“These results indicated that CRP level and LMR were independent contributors to [Parkinson’s]-RBD, with CRP level seeming to have greater predictive value,” they wrote.
Cognitive performance was lower among patients with RBD, as measured by the Montreal Cognitive Assessment and the Mini-Mental State Examination.
“[Parkinson’s] patients with RBD had higher inflammatory indicators and worse cognition; therefore, our results indicate that RBD may affect cognitive function due to increased inflammation,” the researchers wrote.
Overall, the findings “present new information on the role of inflammatory factors in the onset of RBD and provide new opportunities for potential treatments,” they added. “CRP and LMR levels may serve as biomarkers and predict the prognosis of [Parkinson’s] patients with RBD.”