Sleep disorders in aging and dementia

Abstract

This paper reviews the characteristics of sleep disorders found in people at a greater risk of dementia: the elderly adult, patients with mild cognitive impairment (MCI) and those with neurodegenerative diseases. The frequency of sleep architecture modifications and circadian rhythm sleep disturbances increases with age. Although around 40% of older adults complain of poor sleep, true sleep disorders are far less prevalent in healthy older adults and are frequently associated with comorbidities. The sleep disorders observed in Alzheimer's disease (AD) patients are often similar to (but more intense than) those found in non-demented elderly people. Poor sleep results in an increased risk of significant morbidities and even mortality in demented patients and constitutes a major source of stress for caregivers. The prevalence of primary sleep disorders such as rapid eye movement (REM) sleep behavior disorders (RBDs), restless legs syndrome (RLS), periodic limb movements (PLMs) and sleep-disordered breathing increases with age. There are no published data on RLS and PLMs in demented persons but RBDs and sleep apnea syndrome have been studied more extensively. In fact, RBDs are suggestive of Lewy body dementia (LBD) and are predictive for neurodegeneration in Parkinson's disease. Obstructive sleep apnea (OSA) shares common risk factors with AD and may even be an integral part of the pathological process in AD. In MCI patients, the hypotheses in which (i) sleep disorders may represent early predictive factors for progression to dementia and (ii) MCI is symptomatic of a non-diagnosed sleep disorder remain to be elucidated. Guidelines for drug and non-drug treatments of sleep disorders in the elderly and in demented patients are also considered in this review. In healthy but frail elderly people and in early-stage AD patients, sleep should be more thoroughly characterized (notably by using standardized interviews and polysomnographic recording).

P4–021: A hypnic hypothesis of Alzheimer's disease

“…It has been proposed that chronic sleep deprivation and associated neuronal overactivity may directly confer an increased risk of developing AD [26] . Sleep disturbance is more frequent in patients with AD than the general population [36] , occurring in some 25-54% of patients overall [54,58] ; as this is based largely on caregiver reports, it may be an underestimate. Sleep disturbance occurs early in the course of disease [61] and worsens as disease evolves [27,69] , though not necessarily in a simple monotonic relation [39,63] .…”

“…However, converging evidence drawn from molecular biology, sleep neuroscience [21][22][23][24][25][26][27][28][29][30][31][32][33][34] and clinical neurology [35][36][37][38][39][40][41][42] suggests that sleep may interact in diverse and important ways with the pathophysiology of AD. Ramifications of long-term disruption in the sleep-wake cycle could include synaptic overactivity and excitotoxicity [10,21,[43][44][45] , impaired synaptic pruning [46] , failure of synaptic scaling and homeostatic responses [19,20,27,[47][48][49][50][51] , transmission of pathogenic proteins (β-amyloid and tau) [9,15,16] , and disruption of neural circuitry in the vulnerable DMN [6,8,12,21,52,53] .…”

Sleep and dementia

“…However, the three cited reviews in this issue confirmed that our knowledge in the field of sleep disorders in older adults and in dementia has increased in recent years (4)(5)(6). The challenges of coming decades will be to optimize the understanding of the role of sleep in the cognitive process and its potential implication at earlier stages and in presence of particular behaviors in AD.…”

“…Bombois and their colleagues published a comprehensive review on the association between dementia and sleep disorders including insomnia (mainly secondary to medical, psychosocial comorbidities or multiple medications), daytime sleepiness, rapid eye movement (REM) sleep behaviour disorder, sundowning, restless legs syndrome, periodic leg movements and sleep-disordered breathing (4). Etiologies of sleep disturbances in patients with AD is thought to be multifactorial and include components specific to dementia and a number of nonspecific factors associated with the normal aging process.…”

Behavioral management in the person with dementia

“…Bright light (2000 lux) given in the morning can reverse this abnormality and can reduce agitated behavior (63). Sleeping abnormalities, especially sleep apnea, have been associated with rapid cognitive decline (64,65).…”