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    • Despite the prevalence of sleep disturbs

    2018-11-05

    Despite the prevalence of sleep disturbs be set between elderly individuals without cognitive impairment and dementia patients, the progression of MCI subjects with sleep problems to dementia is still undefined. A longitudinal study that accompanied MCI patients for 10 years conclude, as a major finding, that sleeping problems were associated with decrease risk for AD [6]. The authors report that this finding is in contrast with the literature and justified the differences compared to other studies for basically three reasons: the results can varies if is conducted in a A 779 manufacturer or in a clinical setting, may depend on the type of rating scale used and the variability may have resulted from an interaction between age, MCI type, the length of the follow-up period, setting, vascular risk factors and diagnostic instruments. Another data also concluded that sleep disturbances alone was not significantly different between MCI patients who remained stable and those who progressed to AD after 25 months on average [35]. On the other hand, two studies demonstrated that the presence of sleep problems in healthy older adults was associated with the incidence of cognitive decline or dementia [36,37] and another ones identified the relationship between this two condition, as we describe hereafter. To further investigate, some authors analyze the sleep, using actigraphy or polysomnographic, to better understanding what occurs during the MCI patients sleep. In normal aging, there are some changes in the sleep structure as poor sleep efficiency, fragmented sleep, increased in frequency of daytime napping, propensity in fall asleep and wake up earlier and decreased levels of SWS [38,39]. In AD patients, there are the same alterations but in higher intensity [40]. MCI is classified as a transitional stage between normal aging and dementia, then we expected that these patients present the same alterations described in an intermediate intensity. A study that submitted aMCI patients into polysomnographic demonstrated that SWS is dramatically reduced in aMCI, together with borderline changes in REM, REM latency, WASO, sleep efficiency, lower delta and theta power during sleep and reduced stage-2 spindle counts at frontal recording sites [16]. The authors speculate that SWS begins to decline in healthy aging and then declines further in aMCI and DA, whereas in advanced stages of AD, REM decline accelerates such that SWS. A study using an actigraphy in 15 MCI patients also showed a fragmented sleep and poor sleep efficiency, as described in the literature [14]. Despite this results, when MCI patients were compared with healthy elderly controls, a study also using actigraphy parameters, failed to reveal significant differences between the groups, although they observed a trend for phase-delayed in aMCI subjects [15]. This fact possibly occur because the small number of participants (ten aMCI patients and ten controls). These three studies described above that analyze the presence of changes in the sleep patterns also analyze the relationships between sleep and memory and reached interesting results [14–16]. The data that used the polysomnographic recruited 16 cognitively healthy older adults and 8 aMCI patients and submitted the both groups to 2 declarative memory tests (word-pair recall, fact recognition) and 1 nondeclarative memory test (object priming) at night before the register and repeated the tests in the morning after polysomnographic. After 1 week the subjects was submitted to the same protocol. They found that controls improved their recall in the morning relative to that in the evening whereas aMCI patients did not. The same occur with recognition. They conclude that these difficulties in memory processes during sleep are due to the reduction in delta/theta power, which are associated with many types of memory, especially declarative memory that was assessed before sleep, consistent with the speculation that poor sleep contributes to poor memory in MCI [16]. At the actigraphy studies, the authors cannot explore the delta/theta power but they observed that better sleep predicted better memory and when difficult in falling asleep increased, memory decrease. Participants who exhibited greater across-night sleep variability showed lower story-recall during the neuropsychological battery [15]. In another study, the authors recruited 15 older adults that meet criteria for naMCI and submitted them to a neuropsychological test battery followed by the use of an actigraphy for 14 nights. The results of the battery tests and the actigraphy register were related and converged to two important conclusion: greater number of WASO were significantly associated with poorer nonverbal learning, as well as concept for formation/problem solving and greater durations of WASO were significantly related to poorer performance on tests of attention, response inhibition and concept formation/problem solving [14].