Clinical reviewThe relationship between sleep and cognition in Parkinson's disease: A meta-analysis
Introduction
Parkinson's disease (PD) is classified as a movement disorder, but non-motor symptoms are common and have a profound effect on patient experience and quality of life [1]. Up to a decade before the first motor symptoms emerge, patients often experience significant sleep disruption [2]. Sleep quality is strongly correlated with health related quality of life [3] and the impact of PD treatment (levodopa and dopamine agonists) on the sleep–wake cycle is an area of debate, with treatment effects varying between patients and compounds [4], [5].
Sleep disorders affect up to 98% of PD patients [6]. A range of sleep disturbances are common in PD, including insomnia, sleep fragmentation, sleep related breathing disorders (SRBD), hallucinations, nightmares, narcolepsy, REM sleep behaviour disorder (RBD) and non-REM parasomnias [7]. Similar to other neurodegenerative diseases (e.g. Alzheimer's disease) [8], significant sleep problems occur in PD, alongside significant cognitive dysfunction. This is noteworthy as cognitive impairment greatly increases disease burden [9]. Moreover, sleep problems have been shown to contribute to neuropsychological deficits in otherwise healthy people [10], [11], [12]. The cognitive changes observed in early to moderate PD are primarily deficits in executive function (EF) and memory [13], [14], [15]. These are the same domains affected in those with SRBD [16] and in insomnia [17]. SRBD causes sleep fragmentation and hypoxia, leading to daytime tiredness and cognitive deficits [18]. Daytime tiredness has an effect on attention and motivation, affecting neuropsychological test performance [10], and ability to manage daytime activities [19]. Diminished slow wave sleep (SWS) is thought to interfere with the capacity to learn new information [20] and to lead to specific deficits in spatial learning [21].
Given that sleep problems are almost universal in PD, and that they are associated with cognitive impairment even when experienced in isolation, this suggests that the neuropsychological deficits in mild to moderate PD may be compounded by chronic sleep debt or consistently fragmented sleep. That is, cognitive impairment may not only arise directly through the pathology of PD, but also indirectly via the mechanism of chronic sleep disruption. Studies of night-time sleep problems and cognition in PD, however, paint a mixed picture, with many reporting no relationship between sleep problems and neuropsychological performance. Critical appraisal of this literature, taking account of sample size and methodology is needed, as no such synthesis has been conducted.
This meta-analysis systematically examined the relationship between sleep and cognition in PD. The objectives of this study were: 1) to identify whether there are specific cognitive deficits associated with sleep problems (insomnia, sleep fragmentation, SRBD, hallucinations, nightmares, narcolepsy, RBD, and non-REM parasomnias) in PD and 2) which neuropsychological tests are sensitive to sleep-associated cognitive impairment in PD. We analysed, separately, measures of global cognitive function, EF and memory. Additionally, we analysed the sub-domains of memory: long-term verbal recall and long-term verbal recognition and the sub-domains of EF: shifting, updating, inhibition, generativity and fluid reasoning.
Section snippets
Search strategy
Electronic search of Medline, PsychInfo, PubMed, Proquest: Theses and Dissertations and Web of Science: Conference Proceedings databases to 19/12/2013 was conducted, restricted to papers in English, supplemented by hand searches of reference lists from included and seminal papers.
Fig. 1 list search terms which produced a total of 2283 papers. Following exclusion of duplicates and irrelevant reports, judging by title and abstract screening, 43 papers were retained for full-text evaluation. Two
Description of studies
From the 2283 articles initially identified, 16 studies met inclusion criteria. Study details, including methodology and methodological issues, can be found in Table S1.
Across these 16 studies, there were 1882 people with PD. The average age was 66.28 ± 8.65 y, and the average time since diagnosis was 7.17 ± 6.04 y. All studies were conducted in a clinical setting. Mean united Parkinson's disease rating scale (UPDRS) scores were provided for 10 studies, while either mean or median Hoehn and
Discussion
This meta-analysis indicates that, relative to those without sleep problems, people with PD who experience sleep problems demonstrate poorer cognitive performance. Poor sleepers had poorer performance on tests of global cognitive ability such as the Mattis dementia rating scale, and the SCOPA-Cog. When cognition was measured using brief or compound measures (such as the MMSE to measure global cognitive ability, the FAB to measure EF and memory or EF summary scores), no significant effects of
Conflicts of interest
The authors have no conflicts of interest to declare.
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Setting the clinical context to non-motor symptoms reflected by Park-pain, Park-sleep, and Park-autonomic subtypes of Parkinson's disease
2024, International Review of NeurobiologyAnalysis of slow and fast sleep spindle properties in Parkinson's disease – A comparative EEG study
2022, International Journal of PsychophysiologyCitation Excerpt :In the early phase, PD patients show slight executive dysfunctions, but two-thirds of them develop dementia over 20 years (Braak et al., 2003; Zgaljardic et al., 2003). Even sleep disorders and changes in sleep macro- and microstructure themselves might cause cognitive decline in PD (Pushpanathan et al., 2014). The role of NREM sleep, particularly slow-wave sleep in declarative memory reactivation and consolidation has already been confirmed (Rasch and Born, 2013).
Sleep and affective disorders in relation to Parkinson's disease risk among older women from the Women's Health Initiative
2022, Journal of Affective DisordersCitation Excerpt :The role played by sleep in PD risk remains controversial. To date, epidemiological evidence has been mostly limited to small case-control studies focused on PD NMS and to longitudinal studies that examined self-reported sleep-related symptoms rather than diagnosed sleep disorders (Liu et al., 2018; Mao et al., 2018; Mao et al., 2017; Pushpanathan et al., 2016; Wang et al., 2017; Wu et al., 2016). According to Vallee and colleagues, the main risk factor for PD is aging which can be detrimental to cellular homeostasis and lead to metabolic abnormalities such as neuroinflammation and oxidative stress which are in turn driven by circadian rhythms (Vallee et al., 2020).
Sleep alterations are related to cognitive symptoms in Parkinson's disease: A 24-hour ambulatory polygraphic EEG study
2022, International Journal of PsychophysiologyCitation Excerpt :The other domains of cognitive dysfunction are involved only in the latter course of the disease with further spread of the pathology (Braak et al., 2003; Zgaljardic et al., 2003). There are studies suggesting correlation between sleep disturbance and cognitive dysfunction in PD: significant relationship was found between bad sleep quality and impaired long-term verbal recall, recognition, as well as memory and executive functions (Pushpanathan et al., 2014). Excessive daytime sleepiness (EDS), which is common in PD might be also presumed to worsen cognitive performance, particularly executive function (Bolitho et al., 2013).
Sleep, neurocognition, and aging, including secular trends in older adult sleep
2021, Handbook of the Psychology of Aging
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The most important references are denoted by an asterisk.