Clinical features, plasma neurotransmitter levels and plasma neurohormone levels among patients with early-stage Parkinson's disease with sleep disorders.

Background: Sleep disorders occur frequently among patients with Parkinson's disease (PD). Neurotransmitters and neurosteroids are known to be involved in various neurophysiological processes, including sleep development. We aimed to assess the associations of peripheral neurotransmitter and neurosteroid levels with various sleep disorders in early-stage PD.

Methods: Fifty-nine patients with early-stage PD and 30 healthy controls were enrolled. Demographic and clinical data were collected, and sleep conditions were comprehensively assessed with clinical questionnaires and polysomnography. Blood samples were obtained from all participants at 1:00 AM and 9:00 AM. The concentrations of plasma neurotransmitters and neurohormones were detected via high-performance liquid chromatography tandem mass spectrometry.

Results: Sleep disorders were common nonmotor symptoms (81.4%) and coexisted in approximately half of the patients. Dysautonomia was significantly associated with the presence of multiple sleep disorders. RBD was associated with dysautonomia and was negatively correlated with the plasma melatonin concentration at 1:00 AM (r = - 0.40, p = 0.002) in early-stage PD patients. The RLS group had higher PSQI scores, and RLS was negatively associated with the 5-hydroxytryptamine levels (r = - 0.40, p = 0.002) at 1:00 AM and glutamine levels (r = - 0.39, p = 0.002) at 9:00 AM. SDB was associated with cognitive impairment, a greater body mass index, and lower plasma acetylcholine concentrations at 1:00 AM.

Conclusion: Combined sleep disturbances are common in early-stage PD. Dysautonomia is closely related to various sleep disorders, including RBD, EDS, and insomnia. Changes in peripheral neurotransmitter and neurohormone levels may be involved in the development of sleep disorders.