Clinical ReviewSleep disturbances increase the risk of dementia: A systematic review and meta-analysis
Introduction
More than 35 million people worldwide are affected by dementia, characterized by progressive cognitive and functional decline (http://www.who.int/mediacentre/factsheets/fs396/en/). With increases in life expectancy, this number is estimated to double every 20 y, reaching 81.1 million by 2040 [1]. Alzheimer's disease (AD) and vascular dementia are the two major types of dementia. According to the global burden of disease study, years of life lost that are caused by AD and other dementias increased more than 50% from 1990 to 2013 [2]. However, no effective strategies are currently available for treating dementia or predicting its occurrence. Emerging evidence suggests independent associations between different sleep disturbances and dementia. Identifying sleep factors that are related to dementia may help identify individuals who are at risk of developing dementia and inform preventive strategies.
Sleep patterns change as people age. Compared with younger adults, older adults experience less nighttime sleep and have more sleep disturbances [3], [4]. The prevalence of sleep disturbances in older people varies from 9.1% to 69% [5], [6]. The types of sleep disturbances in elderly individuals include insomnia, sleep disordered breathing (SDB), and other sleep problems, such as excessive daytime sleepiness (EDS), sleep-related movement disorder (SRMD), circadian rhythm sleep disorder (CRSD), and nonspecific sleep problems. Specifically, insomnia and SDB are two common problems that affect older adults [7]. Sleep disturbances have a multifaceted influence on health and well-being and increase the risk of morbidity of physical and mental diseases [8]. Moreover, sleep plays an important role in cognitive processing, and sleep disturbances can lead to impairments in cognitive performance in children, adolescents, and adults [9], [10]. Two meta-analyses reported that sleep problems are risk factors for developing cognitive impairment, preclinical AD, and AD [11], and insomnia alone is associated with a higher incidence of dementia in older adults [12]. However, a comprehensive examination of the predictive role of sleep disturbances in incident dementia is lacking. Some studies have reported that insomnia and SDB increase the risk of developing dementia [13], [14], [15], [16], but others reported that delays in sleep onset, difficulty maintaining sleep, early morning awakening, snoring, and sleep apnea do not increase the risk of incident dementia [17], [18], [19]. Several reviews have discussed associations between different sleep characteristics and cognitive impairment and dementia in older adults ∗[20], ∗[21], ∗[22], ∗[23], but the magnitude of such associations has varied across studies, given differences in the characterization of sleep disturbances and various assessments to evaluate sleep disturbances. Moreover, causal links have not yet been convincingly established between different sleep disturbances and dementia.
The purpose of the present study was to systematically review the links between overall sleep disturbances, the most common sleep complaints (i.e., insomnia and SDB), and several types of dementia (all-cause, AD, and vascular dementia) by performing a meta-analysis of longitudinal studies. We discuss the mechanisms that may underlie these associations.
Section snippets
Search strategy and selection criteria
We performed a systematic review and meta-analysis in accordance with preferred reporting items for systematic reviews and meta-analyses guidelines [24]. A systematic search of the PubMed, EMBase, ISI Web of Science, and PsycINFO databases was performed to identify studies that reported associations between sleep disturbances and dementia. The search used the following search terms: (sleep OR sleep disorder OR sleep problems OR sleep disturbances OR sleep quality OR insomnia OR sleepiness OR
Literature search
As shown in Fig. 1, a total of 12,926 papers were retrieved, among which 72 evaluated the relationship between sleep and cognition in adults. Of these 72 articles, 15 identified cognitive function as a continuous variable and reported scores of global cognitive function or a specific cognitive domain (e.g., memory, executive function, etc.). Twenty-nine articles treated cognitive impairment or cognitive decline as the outcome. We excluded six cross-sectional studies and three studies without
Discussion
This systematic review and meta-analysis provided quantitative estimates of the predictive roles of sleep disturbances in the incidence of dementia based on longitudinal studies with large samples and long durations of follow-up. Overall sleep disturbances, including insomnia, SDB, EDS, SRMD, CRSD, and nonspecific sleep problems, were associated with a higher risk of incident all-cause dementia and both AD and vascular dementia subtypes. Self-reported, objective, and diagnostic sleep
Conclusion
Sleep disturbances can enhance the risk of developing dementia. Insomnia may increase the risk of incident AD, and SDB is a risk factor for all-cause dementia, AD, and vascular dementia. These results elucidate the influence of sleep disturbances on the incidence of dementia and highlight the importance of regular sleep in general and in older adults in particular. Future well-designed studies, both prospective cohort and experimental, are needed to confirm the present findings and provide more
Authors' contributions
L Shi, MV Vitiello, and L Lu proposed the topic of the meta-analysis. L Shi, MY Ma, and SJ Chen performed the literature search, extracted and selected articles, performed the primary analysis, and wrote the paper. YP Bao, Y Han, and YM Wang checked the data and commented on and revised the manuscript. MV Vitiello commented on and revised the manuscript.
Declaration of interest
The authors declare no conflicts of interest.
Acknowledgements
This work was supported by the National Basic Research Program of China (No. 2015CB856400), Beijing Municipal Science and Technology Commission (No. Z151100003915121), and Natural Science Foundation of China (No. 81521063).
References∗ (70)
- et al.
Global prevalence of dementia: a Delphi consensus study
Lancet
(2005) - et al.
Prevalence and correlates for sleep complaints in older adults in low and middle income countries: a 10/66 Dementia Research Group Study
Sleep Med
(2012) - et al.
Risk factors for sleep disturbances in older adults: evidence from prospective studies
Sleep Med Rev
(2016) - et al.
The influence of sleep quality, sleep duration and sleepiness on school performance in children and adolescents: a meta-analytic review
Sleep Med Rev
(2010) - et al.
Insomnia and daytime cognitive performance: a meta-analysis
Sleep Med Rev
(2012) - et al.
Sleep quality and risk of dementia among older male veterans
Am J Geriatr Psychiatry
(2015) - et al.
Connections between sleep and cognition in older adults
Lancet Neurol
(2014) - et al.
Can sleep apnea cause Alzheimer's disease?
Neurosci Biobehav Rev
(2014) - et al.
Sleep: a novel mechanistic pathway, biomarker, and treatment target in the pathology of Alzheimer's disease?
Trends Neurosci
(2016) - et al.
Sleep duration and risk of all-cause mortality: a flexible, non-linear, meta-regression of 40 prospective cohort studies
Sleep Med Rev
(2017)
A change in sleep pattern may predict Alzheimer disease
Am J Geriatr Psychiatry
Self-reported sleep disturbance is associated with Alzheimer's disease risk in men
Alzheimers Dement
Sleep disturbance induces neuroinflammation and impairment of learning and memory
Neurobiol Dis
Synaptic activity regulates interstitial fluid amyloid-beta levels in vivo
Neuron
Insomnia with objective short sleep duration: the most biologically severe phenotype of the disorder
Sleep Med Rev
Hypoxia increases abeta generation by altering beta- and gamma-cleavage of app
Neurobiol Aging
Sleep deprivation impairs memory, tau metabolism, and synaptic integrity of a mouse model of Alzheimer's disease with plaques and tangles
Neurobiol Aging
Voxelwise meta-analysis of gray matter anomalies in Alzheimer's disease and mild cognitive impairment using anatomic likelihood estimation
J Neurol Sci
Greater cortical thinning in normal older adults predicts later cognitive impairment
Neurobiol Aging
Epidemiology of restless legs syndrome: a synthesis of the literature
Sleep Med Rev
Periodic leg movements in sleep and periodic limb movement disorder: prevalence, clinical significance and treatment
Sleep Med Rev
Global, regional, and national age-sex specific all-cause and cause-specific mortality for 240 causes of death, 1990–2013: a systematic analysis for the Global Burden of Disease Study 2013
Lancet
Meta-analysis of quantitative sleep parameters from childhood to old age in healthy individuals: developing normative sleep values across the human lifespan
Sleep
Sleep disturbances are related to decreased transmission of blue light to the retina caused by lens yellowing
Sleep
Sleep and aging: 1. Sleep disorders commonly found in older people
CMAJ
Disrupted sleep: from molecules to cognition
J Neurosci
Sleep, cognitive impairment and Alzheimer's disease: a systematic review and meta-analysis
Sleep
Insomnia and risk of dementia in older adults: systematic review and meta-analysis
J Psychiatr Res
Risk of dementia in patients with insomnia and long-term use of hypnotics: a population-based retrospective cohort study
PLoS One
Sleep apnea and the risk of dementia: a population-based 5-year follow-up study in Taiwan
PLoS One
Greater risk of Alzheimer's disease in older adults with insomnia
J Am Geriatr Soc
Daytime sleepiness and sleep inadequacy as risk factors for dementia
Dement Geriatr Cogn Dis Extra
Sleep disturbance and daytime sleepiness predict vascular dementia
J Epidemiol Community Health
Excessive sleepiness is predictive of cognitive decline in the elderly
Sleep
Impact of sleep on the risk of cognitive decline and dementia
Curr Opin Psychiatry
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