EFFECT OF MELATONIN ON PAIN SYNDROME IN DELAYED SLEEP PHASE DISORDER IN PATIENTS WITH PARKINSON'S DISEASE
Authors: Shkodina A.D. 
Published: November 2021

Parkinson’s disease is characterized mainly by damage to the neurons of the substantia nigra and other brain structures and manifested by motor and non-motor symptoms. In patients with Parkinson’s disease receiving dopaminergic therapy, a later onset of sleep has been identified that is associated with the development of the delayed sleep phase disorder. The delayed sleep phase disorder is characterized by a persistent delay in the circadian rhythm that causes a delay in the desired time of falling asleep and waking up. According to clinical guidelines for the treatment of delayed sleep phase disorder, exogenous melatonin is recommended. Along with this, its analgesic properties have been reported. At the same time circadian regulation of fluctuations of painful sensations transmission by either peripheral or central alarm system has been reported. In particular, the two-way connection between the nociceptive system and the circadian rhythm in the human body determines the possibility of mutual influence between these systems. However, the question of the therapeutic effect of melatonin in the presence of concomitant pathology on the circadian rhythm disorders, and, in particular, delayed sleep phase disorder that is a topical issue for patients with Parkinson's disease, is still remaining unexplored. The aim of the study is to compare the changes in subjective perception of pain in patients with Parkinson's disease, who received melatonin therapy and who did not, in delayed sleep phase disorder. We conducted a prospective study that included 48 patients with Parkinson's disease. Circadian rhythm disorders were diagnosed according to the criteria of the International Classification of Sleep Disorders-3. The diagnosis of delayed sleep phase disorder was made on the basis of a clinical interview, filling in a sleep diary and daily thermometry for 7 days. The examined patients were divided into 2 groups according to the chosen method of treatment: group 1 - patients with Parkinson's disease and delayed sleep phase disorder receiving melatonin; group 2 - patients with Parkinson's disease and delayed sleep phase disorder receiving only general recommendations for improving sleep quality and daily functioning without medical intervention. The Unified Parkinson's Disease Rating Scale was used to assess the severity of patients’ clinical condition. The intensity of the pain syndrome was assessed on a visual-analogue scale. The McGill Questionnaire was used to analyze subjective experiences of pain. The patients of group 1 were prescribed to take melatonin, 1 tablet in a dose of 3 mg at 22:00. Individuals in group 2 received general recommendations on the schedule of sleep-wake cycles, light regime and sleep hygiene. Patients with Parkinson's disease and delayed sleep phase disorder have been diagnosed with mild to moderate pain. Treatment of delayed sleep phase disorder in patients with Parkinson's disease reduces the intensity and modality of the pain syndrome, which may be due to improved functioning of the descending pain modulation system and restoration of rhythmic expression of internal clock genes. The administration of melatonin as part of a comprehensive approach to the treatment of circadian rhythm disorders helps to reduce sensory sensations and affective experiences caused by pain that indicates the potential antinociceptive effect of melatonin in the treatment of circadian disorders.