Parkinson’s disease (PD) is a neurodegenerative disease that has various motor and non-motor manifestations. The pathophysiology of PD is linked to the accumulation, aggregation, and prion-like propagation of pathological alpha-synuclein, resulting in the degeneration of dopaminergic and non-dopaminergic neurons. There are both motor and non-motor symptoms (NMS) in Parkinson’s disease including parkinsonism (bradykinesia, rigidity, rest tremor, postural instability, flex posture, and freezing of gait), sleep and circadian rhythm disorders, neuropsychiatric disorders, and autonomic dysfunction.1 Sleep and circadian rhythm disorders are one of the most common non-motor symptoms in PD. There are several causes and associated factors of sleep problems in PD presented in this slide including neurodegenerative process and aging effect, medication effects, and OFF related phenomena.2
Why sleep problems are important in PD?
Sleep problems in PD can be found from very early (prodromal stage) before the motor symptoms and all disease courses. In the prodromal stage, REM sleep behavior disorder or RBD is the most important sleep problem of PD. RBD is the highest risk factor for the development of alpha synucleinopathy. Moreover, prodromal PD usually has other sleep problems including excessive daytime sleepiness, circadian rhythm disorders, and insomnia. When the disease progresses, the impairment of motor symptoms is not only present during daytime but also during night time which is called nocturnal hypokinesia. Other manifestations include nocturia which is the autonomic nervous system dysfunction.2
The prevalence of sleep disorders in PD is nearly 100% but most physicians and patients lack awareness of the association between these problems and PD. Sleep problems in PD are associated with significant impairment of quality of life, not only PD patients but also for their caregivers. In this review, we will discuss the most common sleep problems in PD which is insomnia.2
Insomnia
The definition of insomnia in PD is the same as insomnia in the general population which is the persistent or chronic difficulty to initiate, maintain or consolidate sleep, and/or early morning awakenings, or generating an overall good sleep quality. This problem must be accompanied by daytime symptoms, for example, excessive daytime sleepiness. According to “International Classification of Sleep Disorders (ICSD-3)” the definition of chronic is when insomnia occurs for more than 3 months. There are some differences between insomnia patterns in PD and the elderly. In elderly, insomnia usually presents with difficulty in sleep initiation, while PD, usually has sleep fragmentation and early awakening.
The proposed mechanism of insomnia in PD is due to the degeneration in OD which impacts the sleep-wake mechanism and other risk factors that have impacts on sleep-wake cycles. The insomnia risk factors in PD involve many aspects including nocturnal motor symptoms, non-motor symptoms, treatment, sleep disorders, and behavioral and also mental health.3,5
How to evaluate insomnia?
The clinical interview is still the gold standard for insomnia diagnosis. These should include a sleep schedule, sleep diary, and sleep habits. In addition, the standard sleep questionnaires in PD such as Parkinson’s Disease Sleep Scale (PDSS-2), and Scales for Outcomes in Parkinson’s Disease-Sleep (SCOPA-Sleep) might help but are not specific for insomnia. Polysomnography is not the gold standard for insomnia diagnosis except other sleep breathing disorders, REM sleep Behavior Disorder (RBD), or periodic limb movement disorder (PLMD) are suspected.3
Clinical implications
Insomnia causes poor sleep quality which impacts the daytime symptoms (general and PD-specific symptoms) and quality of life. PD patients with insomnia tend to have more severe advanced PD and are associated with other problems, for example, falling, balance problems, depression, cognitive impairment, poor response to dopaminergic treatments, or more severe autonomic dysfunction in both day and night time.4
How to manage insomnia in PD?
The important first step is to review the possible treatable or modifiable causes such as nocturnal hypokinesia, nocturia, mood disorders, obstructive sleep apnea (OSA), or PLM, and correct them. After that, there are 2 main management approaches, which are non-pharmacological and pharmacological management. Cognitive behavior therapy (CBT) is the first-line treatment for insomnia, others are bright light therapy, sleep hygiene, and regular exercise. For pharmacological management, there are 3 medications; melatonin, doxepin, and eszopiclone which have evidence (possibly useful) in insomnia treatment in PD. 3
Conclusion
Sleep problems in PD are common and significantly impairs quality of life. They are usually under-reported and under-recognized by patients, caregivers, and healthcare providers. Insomnia is also the most common one and causes a variety of impacts. Proper evaluation and management can improve both motor, non-motor, and quality of life of people with Parkinson.
