Early Parkinson’s sleep disorders tied to NfL biomarker in study
Monitoring blood levels could help with treatment, researchers say
The presence of sleep disorders in the earliest stages of Parkinson’s disease correlated with blood levels of neurofilament light chain (NfL), a biomarker of neurodegeneration, in a study.
“This finding underscores the potential of sleep disorders as a robust clinical indicator of neuronal degeneration, closely linked with PD [Parkinson’s disease] progression,” the researchers wrote.
The scientists said prompt identification of sleep disorders and NfL monitoring are “pivotal” for enabling early treatment in at-risk patients, and also could be used as biomarkers for evaluating treatment outcomes.
The study, “Associations of sleep disorders with serum neurofilament light chain levels in Parkinson’s disease,” was published in BMC Neurology.
Sleep disorders are among the most common nonmotor symptoms of Parkinson’s. Often, such sleep disturbances are evident very early in the disease course, sometimes years before the typical motor symptoms of the disease appear. This is known as the prodromal stage of disease.
Study probes relationship of sleep disorders to Parkinson’s development
Indeed, rapid eye movement sleep behavior disorder (RBD) is considered to be a reliable clinical predictor that a person will later develop Parkinson’s. This condition involves a person acting out their dreams during sleep, often with violent movements. Other sleep issues, including excessive daytime sleepiness, also are seen early on in the course of disease.
Still, their exact relationship to neurodegeneration in Parkinson’s is not fully known. To learn more, the researchers explored the association between sleep disorders and blood levels of NfL, which is an established marker of nerve cell damage, early in the course of Parkinson’s disease.
The scientists looked at NfL levels and sleep symptoms among 585 people with early Parkinson’s, 353 with prodromal Parkinson’s, and 175 healthy people, who served as a control group. The data were obtained from the Parkinson’s Progression Markers Initiative (PPMI), a large international Parkinson’s database.
Sleep disorders were evaluated using the RBD Screening Questionnaire (RBDSQ) and the Epworth Sleepiness Scale (ESS), with higher scores on either scale reflecting greater abnormalities.
At the first assessment (baseline), early Parkinson’s patients had the highest NfL levels, followed by prodromal patients, then healthy people.
Early Parkinson’s patients who manifested signs of RBD such as nighttime dream behaviors and arm or leg movements during sleep had significantly higher NfL levels than patients who did not report those symptoms.
Among those with prodromal disease, NfL levels were significantly elevated in patients experiencing disturbed sleep. The specific sleep symptoms associated with elevated NfL levels in both groups varied somewhat by sex.
NfL levels were monitored over a five-year follow-up period. Again, several indicators of RBD in early Parkinson’s patients were associated with increasing NfL levels. Patients with a high ESS score or who were considered to have excessive daytime sleepiness also saw increasing NfL levels over follow-up.
In prodromal patients, daytime sleepiness when sitting and reading was associated with increasing NfL levels in the long term.
Largely, relationships between sleep and NfL were not observed in healthy people.
Increasing daytime sleepiness across several daily life settings over the follow-up period was associated with increasing levels of NfL in female Parkinson’s patients and in men with prodromal disease.
Altogether, “sleep disorders are significantly associated with high levels of serum NfL in the prodromal and early stages of PD,” the researchers wrote.
The data emphasize the importance of timely diagnosis and treatment of sleep disorders for possibly slowing neurodegeneration in Parkinson’s, they said.
“Routine monitoring of NfL levels emerges as an effective and dynamic approach for tracking sleep disorders and PD progression, opening up new avenues for enhancing overall health and quality of life in PD patients,” the researchers concluded.
About the Author
