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The importance of sleep is magnified for patients with Alzheimer disease (AD), who commonly experience sleep disturbances due to changes in their neurotransmitter systems. However, the impact of AD and other dementias on sleep is also seen among caregivers of patients with dementia.
The importance of sleep is magnified for patients with Alzheimer disease (AD), who commonly experience sleep disturbances due to changes in their neurotransmitter systems. However, the impact of AD and other dementias on sleep is also seen among caregivers of patients with dementia.
According to a review recently published in Neuroscience and Biobehavioral Reviews,1 sleep abnormalities affect 25% to 60% of all patients with AD and are often some of the first symptoms of the disease. Specifically, these patients experience fragmented sleep-wake cycles, causing longer and more frequent periods of awakening at night and naps or decreased alertness during the day. Potential mechanisms of the relationship between AD and poor sleep center around imbalances in levels of several important neurotransmitters, including glutamate, noradrenaline, serotonin, and acetylcholine.
Reduced total sleep time is part of the normal aging process, but it can cause cognitive function to deteriorate, especially by disrupting the memory consolidation process. Considering that sleep-wake disturbances are magnified in patients with AD, poor sleep may exacerbate the cognitive decline seen with the disease.
The review also noted early evidence suggesting that the sleep-wake cycle is a potential driver of developing AD through the accumulation of β-amyloid. Due to the limitations of those studies, the review authors wrote that there is more evidence that amyloid pathology alters the sleep-wake cycle, meaning that “sleep abnormalities, in the presence of a disrupted [β-amyloid] metabolism, are probably not the initial causal factor of AD. However, poor sleep might still be considered a risk factor for the further progression of AD.”
In this sense, disrupted sleep may create a feedback loop of β-amyloid deposits, disruption of the brain’s sleep centers, increased β-amyloid levels, and further worsening of sleep.
“When multiple neurotransmitter systems start to fail, as in neurodegenerative diseases like AD, the sleep process does not stay unaffected,” the review authors concluded. “By consequence, AD patients often present with severe sleep and circadian disturbances.”
Poor sleep is not unique to patients with Alzheimer, however—it also is seen among their caregivers, according to results published in JAMA Network Open.2 A systematic review and meta-analysis extracted data from 35 studies to analyze the sleeping patterns of 3268 caregivers of patients with dementia, including AD, and compare them with 696 control subjects who were not caregivers.
The investigators found that caregivers had 0.29 SD less total sleep time, on average, than their age-matched noncaregiver controls, which equals about 2.42 fewer hours of sleep per week. Self-reported sleep quality was significantly poorer in caregivers than controls by a difference of 0.66 SD. Analysis of studies of sleep interventions, such as sleep hygiene education, revealed that caregivers had better sleep after completing an intervention compared with those who had not experienced an intervention.
The review authors posited that there could be a bidirectional relationship between sleep and dementia caregiving, in that caregivers may have trouble falling asleep due to the stresses and demands of caring for someone with dementia, and they may also experience difficulty in carrying out their caregiving duties due to the negative cognitive and physical effects of poor sleep. The authors also noted that the accumulation of sleep debt over time is associated with lower β-amyloid clearance, which may increase the caregivers’ risk of developing AD or dementia.
“Given the long-term, potentially cumulative health consequences of poor-quality sleep, as well as the increasing prevalence of dementia and the corresponding need for caregivers worldwide, clinicians should consider sleep interventions not only for the patient with dementia but also for the spouse, child, or friend who will be providing care for that individual,” the study authors wrote.
References
1. Van Erum J, Van Dam D, De Deyn PP. Alzheimer’s disease: neurotransmitters of the sleep-wake cycle. Neurosci Biobehav Rev. 2019;105:72-80. doi: 10.1016/j.neubiorev.2019.07.019.
2. Gao C, Chapagain NY, Scullin MK. Sleep duration and sleep quality in caregivers of patients with dementia. JAMA Netw Open. 2019;2(8):e199891. doi: 10.1001/jamanetworkopen.2019.9891.