Objective: To clarify if impaired melatonin secretion is associated with daytime or nighttime sleep disturbances in patients with Parkinson’s disease (PD).

Background: PD is associated with various kinds of sleep disturbances such as insomnia, interrupted sleep, early awakening at night,  and excessive somnolence during the day. PD is reported to be associated with decreased melatonin secretion. However, the association between sleep disturbances and impaired melatonin secretion in PD is not well known.

Methods: This study comprised 32 patients with PD and 13 controls. Salivary melatonin levels were measured using ELISA; the saliva was collected noninvasively in the morning (8-9 AM), day (2-3 PM), and before sleep (9-10 PM). We used the Parkinson’s Disease Sleep Scale (PDSS) for assessing nighttime sleep disturbance and the Epworth Sleepiness Scale (ESS) for assessing daytime sleepiness. The association between salivary melatonin levels and the PDSS and ESS scores was evaluated.

Results: The controls did not show abnormal melatonin secretion rhythms. However, patients with PD showed paradoxically increased salivary melatonin levels in the day, which were normally suppressed. The ESS scores and salivary melatonin levels were significantly correlated in the day: patients with higher ESS scores had higher melatonin levels in the day (R＝0.55, p＜0.05). The PDSS scores and salivary melatonin levels before sleep were negatively correlated, indicating that patients with higher PDSS scores had lower salivary melatonin levels before sleep (R＝0.58, p＜0.05).

Conclusions: We found correlation between salivary melatonin levels and PDSS and ESS scores. Our results suggest that impaired melatonin secretion is associated with sleep disturbance in PD. Patients with PD with higher melatonin levels in the day showed tendency for daytime sleepiness, indicating that high salivary melatonin levels could be an indicator of daytime sleepiness. We found negative correlation between PDSS scores and salivary melatonin levels before sleep, indicating poor sleep quality in patients with higher melatonin levels before sleep. This may be explained by the possibility that the peak melatonin secretion, which is usually observed at night, while sleeping, in healthy individuals, may occur in early evening or even during the day in patients with PD. Further observations with saliva collection in the night during sleep may be necessary.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/association-of-impaired-melatonin-secretion-with-sleep-disturbance-in-parkinsons-disease/